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Home My WebLink About911793.tiff • 05:11:91 09:35 $'614 833 9173 Y.A.1t.S.- CORP. O002 Mid-American Waste Referenc Inc. Regulatory Agency g Ms.Linda Welch thief,Division of Solid and Hazardous Waste Management ‘ Ohio Environmental Protection Agency 1800 WarerMark Drive Columbus,Ohio 43266 (614) 644-2917 Mr.Bruce Pain y Chief,Solid Waste Management Branch Indiana Department of Environmental Management I 105 South Meridian Street i Indianapolis,Indiana 46206 I (317)232-4473 Mr.Anthony Orlando Regional Manager,Bureau of Waste Management, Southwestern Region Department of Environmental Resources 121 South Highland Avenue Pittsburgh,Pennsylvania 15206 (412) 645-7100 Mr. Shelby Jett Manager,Solid Waste Branch,Division of Waste Management. Department toafirEnvironmental nv Offs e P t kl Protection 18 Reilly Road Frankfort,Kentucky 40601 (502) 56-6716 Ms.April Gruntsky Staff Engineer,Bureau of Solid and Hazardous Waste Management South Carolina Department of Health and Environmental Control 2600 Bull Street Columbia, South X9176 a 29201 Mr.Michael Fitsimmons Waste Program Administrator Florida Department of Environmental Regulations 7825 Bay Meadows Way Suite B200 Jacksonville,Florida 32256 Mr.Kim Pritchard ' EXHIBIT Supervisor,Solid Waste Office Sg Nest Virginia Division of Natural Resources 0 . - 1 1394 Hanford Street "win 1 7 199i .Charleston,West Virginia 25305 (304) 348-6350 ,E f 911.793 Veld C6. Amain�m 05/14/1991 11117 FRO, ehchant Flick Assoc. TO • 13034571349 P.02 refit Mid-American _� P-0. 6ca 156 Lanai'.vmerasaw Ohic 13110 elf4, Waste Systems Inc. (61418334t55 (814)833-9173 FAX ;614)633.2199 FAX __ SUBSIDIARIES Acme Waste Systems,ins Girard Point Transfer StaBan Mid-American Systems,Ins. Mid-American Wass Systems of ?.C.Sts 4M 7600 South 26th Street Fier a2 Suie 300 Pavilion Florida,Inc.dba Finevest Landfill Oltsa ,'r g)63 4568 Pfillacie(215)1 3-41 0 19145 515 North Fla*Drive e Centre • ✓ 4348 South Pairs Boulevard Ste 101 •0'6".1 m(21 38.4568 (215)463.4170 West Palm Beach.FL 33401 Jacksonville.FL 32218 Arta 215)613-4266 145 FAX(263.7195 (904)296.1400 Fs {2'Sj 633.4266 FAX(215)•163.1068 (107)833.5445 rgos)296.31x7 FAX Bat Borers.GM Mice K:ec)L GM (407)833.5446 comp dial-In _Ray Pontine.Marketing (407)659.7677 FAX Jim Amnia,GM United Was a Systems.Inc. (407)346-S266 MOBILE Ca Landfill Sabatini Transfer Station Jon. 7 Stsiod aRoutLandfill Route County Box 467 31ata Route 328 Rana 5,Road 140 Ii+,7tMAmedan Weaa Systems Box 326 UFaver Hill Road ` cAnhc:,Crio 45651 P.O.Box 1264 Elitism Divisional Office Chase/00A 15024 Office (514)595.55S0 / Penland,Indiana 47371 795.20 Pine Valley Drive (412)265.2080 Ater Sam(614)596.5383 Office (219)726.2871 PO:burgh,PA 15239 (412)255.3833 FAX Fax (514)595.2.64 Fax(215)726.6584 (412)327.7750 Jerry Saomini.GM 0Mi Graves.GM Mike Luken,JaneAnn (412)327-T149 FAX Sanitary Commercial Services Marchetti 1841 Sraah Bridge Read Buz/Mint Refuse Services,tea John1006sat utSlraet,Mc. p ny(TTC,Inc.)3435 Trees y:ewn Road 1008 Walnut Slraet Mound Come Inc. Jackson.Ohio 45140 Colmar,Pennsylvania 18915 P.O.Box 182 P.O.Box 12 08Ica (614)286.2430 P.O.Box 5002 Canal%rimester,Ohio 43110 1612 Salem Road Tell Free 600-752-3760 Larzdate,PA 19446 Office (6111833-9111 South Salem.Ohio 45581 Fax (614)2 �.+2 Offaa (215)222-5875 After Spm(614)883-9113 (513)981.4223 1 After 5pm (215)622.5879 Toll Free 800.3430047 (513)981-2171 After 5pm South Wens Landfill Fax (215)822-3790 Fax (614)833.2199 FAX(513)981-1564 Bruca Wunder,GM,Pal Kelley,OM Sun Bowman.GM,Stara Brewster,OM Mite Shelton.VP,Bill Ogiesbee,GM Route Gh�West • 46768 Cantar Point Landfill Johnson Transfer and Mound Transfer Station - / Mika Luken,X148 P.O.Ecx 9 Recycling Canter 195 Seney Road M GM Rwa1 Roue C2 100 Ecology P.ow, ChiScothe.Ohio 45750 J Canter?cct.IN 47840 P.O.Box 4042 Olarn ysbe3.GM Trig SabmnRoad fill Inc. (an)23x•2068 Newark,Ohio 43055 BM 09 South Salem,Ohio 15681 (812)835-46e)FAX (614)345.3250 ' George KcGmeyer,Sito Mgr. (614)345.1500 After 5pm North Shore Waste Control,Inc. / Office (513)981.4223 (614)345.0662 FAX 10.5 Skokie Valley Road Char 5pm (513)981-1117 Deep Valley Disposal David Wilburn Lake Bluff,Illinois 60044 Fax (513)9814564 Oid Staubenviao Pike Office (708)831.3030 Banff Black P.C.Box 157 Lee County R►gional Recycling Fax (708)2342798 Oakdale.PA 15071 and Dispatch Facility After 5:00 (708)234-•4445 Tri•Valley Waste Systems,Inc. 112)788.474? 109 East Church Street George Moorehead,Kevin McKee 2154 Greensburg Road (' e. Tom Lima,GM New Kensington.PA 15068 Pat Fleck,GM (803)484.6 SC 290]0 office (112)339-4458 (803)484-6173 Fairfield Sanitary Landfill,Inc. . Jim Amon North Walls Landfill Fax (412)339-3934 10110 Hedge Road J 0443 West 1000 Nonh Emir Hershtled,GM Amanda,Ohio 43102 Local Sanitation Ossian,Indiana 46777 Cf ice (614)969.4757 P.O.Box at KY 4801 alias(219)638-4568 Valley Landfill • (614)963.2940 Morehead,Komucky 40351 Fax(219)838-4268 .R.D,e2 Sox 282A Howard Campbell GM (806)784-8544 Maw Luken,GM,Mice McBride.OM Smart Valley Road M06)7 , hwin,PennsyNania 15662 Galtta County Landfill Steve Hodges.GM Northwestern Landfill Office (412)7��6 . / Roush Hcilow Road P.O.Box 1523 • Ga8opo5s,Ohio 45631 11M-American Systems,inc. � Patkersburg,WV 26102 Dewey O iinski,GM (614)328.9740 1006 Walnut Sitter 422.6293 P.O.Box 156 • (304)428.7810 FAX Wellston Landfill Gary Sanitary Landfill Canal Winchester.Ohio 43110 Howard Campbell GM .i Frank Smith Road 1903 Burr Street Office (614)833-9406 Wellston,Oho 4569b 1 ,ft�1 '1! Gary.Indiana 46404 Fax (614)833-2178 (614)3840925 • (213)944.1077 Michael Patton,Ron Ouian e Mid-American P.O.Box 15€ Cana(Winchester, Ohio 43110 Waste oystems, Inc. cs,4, 833-9155 CI ..—....1) ar imillIME=IIIMm..MIIIII0M. ..8. 010•10iiiimir PENNSYLVANIA OHIO INDIANA IRd•Annetiean Waste Systems National Waaro 5 teeny Corp. Fairfield sanitary Landfill,Inc. Mare*Landfill,Inc- IGd-American Waste System of Pym7draniz Inc.dta dba Valley Landfill • 101:0 Hedge Road 1612 Salem Road - of Indiana,Inc.dba Id-Valley Wade Systems RD$2 Box 25-1 i Nnsnada; Oho 431C2 South SalrgOhio 45681 - Aare Waste System 2154GreesaulgRoad • Pleasant Way Road • f614)9694757 (513)9814223 0143West 1003 North Now Keminran,PA15068 mn,PA 64 A -Jason Dale: 2:87 Acquisition Data 120 P.O.Box 403 • (412)359-4458 (M2)744-7146 Can= Sob Sim= Contact ea OBNsbee Oasis&Moans 46m - Asp aaion Cam 4189 ACW6itiar Data: WU (219)6364568 Contact Either Heshflofd Conact Dhana()WN l Johnson Olsposal,Inc. United Was*Systems,Inc sibs Acquisition Dar: 2188 i0C6 Meant Street A91ad Landfill Contact Bab Boers Mb-hericae Wasa*stems Midamencan Waxx Systems P.O.Box 182 Box 467 Sena Route 328 , al Pennsylvehi4 Inc.dba of Pereaylvana Inc.dba Cara:Win urstur,Ohio 43110 MrJMhur,Ohio 46651 B 6 L Wismar.Inc:dba BumMont Refuse Santos Deep Valley Disposal (814)8334:11 (eta)526- 90. NdHt Wells Landfill 3435 Treat=Road Ob SattbenwNe Pike Aepuoiten pate: 196 Acqueitan Date: 4188 (033 West 1000 North • Calm*,PA 18915 P.o.Box:57 Corns= Txm Lau Correct Don Grins Oulu Indiana 46777 (215)922.5875 CakeW4.PA 15071 (219)6354568 Acquisition Due: 5/58 (4.12)788.4743 1pd-Anaeiesn Systems,too. Johnson Dna=Ina ha Acquisition Ore: 5/88 Cantata: Pal Kelly Acquit+ion Da*:5,90 1006 Waver-Stray Johnson Transfer and Contact Bob Wads Contact Pat Pack P.O.Box 154 Recycling Center M!d-Amar:on Wste System Carol Wrrhoster,Ohio 43110 100 Ecology Row - Center Paint Landfill,Inc. of Peesyt ana Inc.dba Mid-Amen=Waste Sys:arrs (614)833.9406 P.O.Box 1042 P.O.Box 8 RR*2 Girard Pohl Translar Station of Pennsylvania.Inc Ma A.;:siton Dew anti Nayarit Ohio 43055 • Center Point,Lmtkna 47840 3500 South 26th Street Plan Ferraro Trimly,Station Cat= Mike Paton (614)345-9250 (812)835-2068 Philadelphia.PA 19145 Rant Box 3C2 Acquisition Dye: 5/89 Acquisition Data: 690 (215)4631170 teaming,PA 15201 Mir:Amedm Was*Sycams Corr= Tim Iwo Contact Andy Kramer kquistion Date: zee Aro/tsar,Oa: urea at 0;*,Ina dhz Cam= Mike Kreck Mamd Company • Mid-Amen:a Was*Systara Mid-Amen=Waste Systems Ltd-Amen=Waste Systems P.O.Box/2 of Ohio,Inc of Indiana.im dba 55d-American Waste Systems of Penrsylvani ,Inc.dba :612SatanRoad Roan Train'erSuntan Wry Sanitary Landfill Easam Divisional Office Sabatini Transfer Station South Salem,Ohio 45681 7450 Oak Leaf Ana.* 1900 Bun Street 795.30 Pine Valle/Drive Box 3.16 Leaver Hit Road 1513)901-4223 Oakwood,Otto 44146 Gary,Indiana 48404 Pittsburgh,PA 15039 Cheswick PA 15024 kansitar Date: 12187 Acodotton Oar 9190 (Z9)944-1077 (412)326775C (412)265.2080 Conan: Bill Oglesgm Contact Jim Bowman Aequeition Daa: 690 Contact Dennis Marched Acquisition Date 290 Contact: Wily Smith lae•Amenan Waste Systems Mid-Amrxiaal Was*% ams of Ono.Inc.aba H 6 D Fxeavatrq,Inc dba - • of Pennsylvania,Inc.dbe Mound Transfer Station County Landfill > Retttiehausen Ref**Sams 195 Stray Road $OUTIi Rate 5 Road 140 KENTUCKY. P.O.Box 159106-4 Cieudni"e,oho 45750 • CAROLINA P.O.Box 1254 •Frzburgn PA 15241 Paden,Indiana 47371 Local 6enitdlm,Ina (5:4)374-3500 Acuisition Data: 1,291 726-2871 Les Counry Regional Ken**Rasa 801 A=a:tan Data: Ina (219) P.O.Box 484. Canx� 8i C5iesbco 0309 Eat Churn,S�vaetok Fad6ty Contact Da W.Walls Morenead.Kerrrky 40351 Contact Bob Walk (606)7&-6544 Mid-Ama:imr.Wasat Systems BkhoM^Ila.SC 29010 r'Olio.Lea. `d.x+ (803)4844173 H S 0 Excavating,Inc be Acquisition Dam: 5/89 of Oita.Lno d* raw Services Acquisition Date: South Wells Landfill Comte Steve Hodges EWESTVIRGLNL VIRGLNL1811 Sraith Bn9e Road Comaet Jm Arnold Rcae a1,203 Washtern Disposal Co,IJsisa:Ohio 45540 Liberty Center,Mdiara 46765 Emt Dry Run Road(614)286.2430 (219)8944148 1523_ Acquisition Dax: 70180 �� r9.WY 3i1 C2Acquisidr.Data: 1288 _ Contact: Bob Walk 9332Comer_ Jonn monger FLORIDA ILLT�i TOLS n Dare: 1c50Mound Landfill,Inc eta Mid•Amonan Waste SystemsMid-American Wale Systems ike Peock.raullm9Wok County LaIdf19 Md-Amenan Waste Systems of Indiana,Inc dba on Graves*nal of Illinois,Inc dba of Florida,Ma dbe Craw(overfills Transfer Station Noroehore Wute Cartlrcl Aotsh}b"vw Road • rower=Landfill LP. 513 Bluff Street GalGpow,Ohio 45431 (55%general partner vh*reN •Craw(rdevide IN 47933 105 Skokie Valley Road (fi!<)38697<0 Inception Dale: 1/9 Acquisition Date: 11,5/90 lake DNS sins 50044 Arauisimn Ora: 12'98 Comaet Am Arnold y ait& (708)831.7030 Contact And g NEW JERSEY Con= Don GM= Acquisition Oa*: 12169 MLd•An*danSy:ten tInc. Contact Tom Late ASOMialec,Inc. R028ox339 Mot d Lintz'',Inc dim Suite 330-Pathan Phillipsburg W 08845 Walston Landfill Daubs Canna Daubs Landfill Ma p1 BSS6269 Frank Smith Read - 515 Non h Nagler Dive P.O.Box 391 ( uisitcn Data: 391• lYaecmn,0.tio 4-5692 West Palm Bead.FL 33401 Fairfad County,Ufincif 62837 Aoq i6:41354.5924 - (518)847-4712 Coot= Art Bossing Aca=ion Dm net 1407)837.5445 .Acquisition Dater. lain Camas Don Graves Mk•Pam Canna Jena Baron- Contact As of 4/1/c _..`_ el if P.-1 `-.) 572-2- ei I Ex k;b:f 51 s w heap of tkereferee, reeled �' am) sol= 42 Wa.s+e- 7-4e ma,r Slows A 0614 1e-r, //M'' ;Pe r IA N di f'kc L f �/, "rhe c l.r K -k `Lc VeAr., aF IA N41 (-oMM:r. v�/tO AA T^II /►1 r, S1 AtS1 n, MAY-21-91 TUE 14:29 HMWM FAX N0. 30?"^14401 P. 02 _ STATE OF COLORADO ___ COLORADO DEPARTMENT Of HEALTH ° .' s. •a 4210 fast 11th Avenue rekracc '. Denver,Cotdrad0 B0220-37 16 (3031 3224076(Main Building/Denver) . � �� . Phone (3031 320-8333 003)320-132B(PtarmiganPIaNOetnrey . 0 031 248-719 0(Grant function Regional Office) ,74 s Roy Romer Governor Thomas M Vernon.M.D. May 17, 1991 fsecueve o6ettor Chuck Cunliffe, Director Weld County Planning & Zoning Office 915 10th street Greeley, Colorado 80631 Project: Solid Waste, ERD Inc. , Southern Weld County. Dear Mr. Cunliffe: I know that members of the Solid Waste staff in the Colorado Department of Health, Solid Wasce program have prepared, documented and provided technical to you and the county commissioners their comments and concerns with regard to this facility; so I won't need not repeat these issues at this time. I would, however, at the request of Mr_ Ted Zigan, like to take this opportunity to write to you concerning the potential benefits of the treatment and service included in the proposal for the ERD Inc. site and facility. As a concept, this Department supports the development of integrated solid waste systems and strategies. It is heartening to see proposals for new solid waste sites and facilities which include recycling, materials recovery and waste stream diversion mechanisms prior to final waste disposal. The advantages of increased flexibility in solid waste management systems is recognized by private industry. It is exciting to see sites proposed in Colorado to addross this issue and to have site owners/managers with the forethought to include these elements in their initial application for a certificate of designation. The long term benefits of this type of diversification will be proven by the success and successful operation of facilities like the ERD proposal. 4 a EXHIBIT LLre—a,' 2 i A4%, . 01 r;:� . . i. 5/2.1/5 I EXhI-f- 61 15 A. voz. +APB of o. S'ot.'e.9 WAr+e, di Slo f or:+-C (Vct qty Lamd f //) /6eiti IN fact-hi-wet-fit-cm fe nay/vet nilv1/4. , ^I l.e anic Srs.rJ IF CON NF Y (AMn^Iff;IN[/I 1iAS �� v GQ- 1 February 20, 1991 Hazardous Materials 6 Waste Management Division Colorado Department of Health 4210 East 11th Avenue Denver, Colorado 80220-3716 Dear Ms. Buckingham: The purpose of this letter is to express our objection to the proposed Zigan landfill and recycling center. The reasons for this opposition are numerous. Future land use potential, residents' nuisance concerns, residents' safety and health concerns, and certain geologic conditions which increase risks to the environment and the residents. The past history of the area raises questions of the consequences of improper or inadequate planning and oversight. The two current landfills have made the residents familiar with the negatives associated with these operations. Any landfill has inherent problems - rodents, bacterial infections, air contamination, methane gas buildup, hazardous materials from households and small quantity generators and likely groundwater contamination. "Higher levels of contamination and thus, higher risks are associated with larger facilities that have a greater mass of waste." "All other factors held constant, risk decreases with increasing distance from the facility." These are quotes from the proposed EPA Solid Waste Disposal Facility Criteria, page 3393. Therefore, we urge the Colorado Health Department, in rendering a decision on the Zigan proposal, to consider the significant effect on the human and natural environment which will result from the addition of yet another landfill in a limited geographic area. Within a mile, there are presently two operating landfills. A proposal for another landfill is pending CDH approval within the immediate future. We strongly urge CDH to review the Zigan proposal not as an isolated landfill application, but rather as one factor in an equation that will result in significant environmental impact. When viewed with other existing and reasonably foreseeable actions, the environmental consequences of four landfills, covering 620 acres, in immediate proximity one to the other, is profound. The existing Laidlaw Landfill, which is located across the street from the proposed Zigan facility has been documented as leaching toxic waste. EPA investigation of this site is underway. The proposed siting, like the existing landfill, is located directly over the Larimie/Fox Hills aquifer which services several drinking wells in the vicinity. The existing and proposed landfills all are situated within a triangle made up of residential dwellings. The risks of subsidence or geological instability which may jeopardize this precious water resource in Colorado necessitates a heightened. level of agency scrutiny in consideration of such a location. Associated with this high density of landfills and the additional recycling center, is, and will be, a large volume of heavy truck traffic. Problems associated with this have been numerous already - danger from traffic, increased dust, and trash escaping trucks. Quiet country living with joggers, horseback riders and schoolchildren waiting for the bus, can be endangered on the narrow dirt roads or fast, smooth paved roads. One woman testified in Erie about a truck overturning in her yard and burning. Dump trucks drag racing in nearby eastern Boulder County were also mentioned in testimony. Laidlaw's July 12, 1989 traffic count was 428 in 18 hours. Zigan estimates 200-250. This represents a tremendous impact on this small area. • EXHIBIT ? '� A., Z , za •c -�, _o+ TI7C • _. ,n Fn1.;M NO. 3033314401 n- May 1: , 191 = Page 2 I hope that this site is one of many proposed for areas throughout the state that will provide alternatives to therlandfilling-only concept of waste management. I also hope that existing sites will continue to upgrade and diversify that range of services to reflect the increased public demand for comprehensive waste management and waste minimization. Thank you for your efforts in this area. If there are any questions that you would like to address to me or my staff feel free to call at any time. no ely, • if•Pa a a Chi Solid Waste & Incident Manageme ection Hazardous Materials & Waste Ma gement Division i.:aY 2 1 1991 Ileld to. Pbaget DISS Sl.f:M;i3J) page 3 Why are there no monitoring wells located in the center of the plot going down below the landfill liners? The operator, Mr. Paul Zigan, has no experience in this field that is known to us. We are told his gravel pit operation in Adams County has not been rehlaimed, as per his agreement with the county. We would hope you would question his ability, resources and integrity in completing this project properly. With such serious consequences possible, the operator's integrity certainly must came into consideration. Although the idea of the MRF appeals to all, we suspect it as a ploy. What guidelines are followed to ensure health and safety at these plants? The OEC told us the effectiveness varies widely - depending on the operator. The last point concerns the fact that this is obviously a large metro-area regional landfill, as the others in this area are today, and should be evaluated on a larger regional land use scale. Landfills of this size should not be located this close to a municipality on the verge of growth. The Comprehensive Plans of both Weld County and the Town of Erie, as well as other nearby growing municipalities, recognize this section of Weld County to accommodate future urban growth. Clearly, such a goal will never be realized in the midst of landfills. We apologize if any of this information or comments are not pertinent to your consideration of this application. We are not totally clear on the guidelines. We thank you for your consideration of the questions and information we have presented. Enclosed is a copy of a map taken from a report by T. L. Davis and R. J. Weismer at the Colorado School of Mines entitled "Late Cretaceous Growth Faulting, Denver Basin, Colorado" which shows the heavy Boulder-Weld faulting areas. If a copy is needed, we would be glad to supply it. Sincerely, S.E.E. (Safe Ecological Environment) (This group represents Concerned Citizens of Erie and Parkland Estates. ) Board Members: Janice Whalen, chairperson Tom Konetski, vice-chairperson Dick Medenwaldt Marilyn Silver Alternates: Don Brand Toni Salz Other active members of Concerned Citizens of Erie wishing to sign: Marilyn Brand Pat Rice Virginia Blacker S.E.E. P.O. Box 562 Erie, CO 80516 Phone Contact: Janice Whalen at 665-6870 Public Information Meeting Q ilACrATA Response to Questions April 6, 1989 QUESTIONS SUBMITTED BY THE CONCERNED CITIZENS Question 1. Are the uninspected early cells near monitoring well 103A and B possibly the source of the volatile organic compounds leaking onto Union Pacific land to the north? All of the cells were inspected before any refuse was placed. In addition, all' excavations were made to design grade using standard earthwork level survey control. wT.,je.. othesized •<releas4- of '-volatiles` from the'filh'x= as ASeakage =through '-the :diner: This is evidenced -* the absence of volatiles in the bedrock ground water at the site boundary. Therefore, if the volatiles were released from the fill, the'teleasew:must~-have- occurred-"as leakages;throughahe sidewall not the liner. Question 2. Does this plume of chemicals near the 103 wells indicate the clay liners are not able to contain material effectively? Please refer to our response to the previous question. Question 3 . What is the likely original source of the chemicals found in wells 103? The _:chemicals . found -'in the .samples from .the. _103. wells: were" likely--introducedn: the- fill -.as . very , small quantitiesitafrom:c householdsn3Dusihessas. " The,.chemicals_ are-_constituents .af degreasing solvents,. 4insecticides, ., paint>, .removers, 4-aerosol prope7,lants:tenedrifr::cleaning _fluids ::: In -addition,.,they en,.be t- created by :=:microbial digestion .of :municipal. refuse-during r methane' `generation. Question 4 . Are these types of compounds allowed in the landfill? Household hazardous wastes are allowed in all municipal landfills. EXHIBIT : - a79eikte 3. r flay 17, 1991 To: Weld County Planning S Zoning Commissioners Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We vould ffitbsi.•to voice our oppositfaa to-this proposed 200 acre landfill and recycling fr�-i itY andtbrdng to your atteatfon:some of our concerns. We had hoped to see an end to the lnflowilts in this area which' are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Blowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences Air pollution - small quantities emitted rith methane gas -Water ccaramination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. .Ranch Eggs Estates and Leisure Living subdivision are residential developments and fanm lees than 1 mile from the development. The :residential portions of Erie are slighftti over a mile. - • The Town-of Erie is'opposed tki ti 8 8.D.. proposal and the proposal is definitely within Erie's Urban Growth Ek mdary 4These landfills serve the entire metro area not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area bas better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Res fully submitted, - M/7,) .Gcl%-2`= 071 Ay f9 r i Q Cam. -6 76 #° ' ,t"i,,z_. at„,z \ _ page 2 This being the highest elevation within two miles causes additional problems. It seems logical that any contamination will not remain easily contained. The high visibility makes it difficult to screen from view, noise and lights. The current sites already carry bothersome noise to the old part of Erie, about 1k miles away. Winds are logically more intense - which means more blowing trash and a more unattractive blight. Prevailing strongest winds carry the litter generally to the east, where the residences are closest to this site. Zigan estimates that it is only 800 feet to the nearest residence! This will tend to carry noise, odors, as well as the blowing trash and contaminated air. The other predominant wind direction is from the southeast - which leads to the older part of Erie. The omission of wind data in this application should be corrected. We dispute the applicant's statement on page 10 DSR "the geologic setting of the property makes it an excellent candidate for environmentally sound landfill construction". Gustayson Associates' report dated February 12, 1991 contests this statement with discussions of high probabilities of faulting and seismic impact. The geology in the area has not been adequately characterized with thorough sampling p.oceddres to prove its superior candidacy. On the contrary, geologic information points to its irrational location - unless it's based on markets and accessibility. Although the undermining in the area was not addressed by Gustayson Associates in the report on this application, we still feel that the proximity of these mines could prove to be an easy conduit for any contamination to spread - esp. considering the faulting mentioned by Gustayson Associates. Also, the studies which were relied on for landfill boundaries were not based on any geologic testing. Following are a few quotes from the March, 1975 Amuedo and Ivey study on the Boulder-Weld Coalfield. "Prior to the design stage of many projects, it will be necessary to gather additional information on the subsidence hazards of specific properties. This information will be mainly obtained from core drilling and geophysical surveys, and its acquisition is likely to be expensive."(p. I-2) "Given the above factors, it is estimated that mine limits are within 500 feet of Where they are plotted in at least 90% of the instances."(p. V-2) "Factors such as angle of draw, attitude of bedding, and presence of zones of weakness due to faulting can extend the surface influence of a particular void well beyond the limits of the undermined area. Determination of the extent of subsidence at the surface is further complicated by the possibility of significant inaccuracies in the original mine maps."(p. VIII-10) The applicant has Changed the border of safety given by the Amuedo and Ivey study. We believe this liberty taken is not prudent. The angle of draw used by the Amuedo and Ivey study was 35 degrees, so we dispute the applicant's supposed throwing in an additional safety factor (p. 30, USR) . The applicant should be required to prove that there is no undermining on the site with systematic patterned drilling. The coal seam mined at the Columbine probably continued on either at a higher or lower elevation at the fault line encountered. Coal seams could ease liquid migration. We question whether the coal seam mentioned in the applicant's report is likely to be discontinuous. Will any natural resources of coal and natural gas be recoverable after the landfill covers the area? The thickness of clay at this particular site is certainly not unique in Colorado. Also, the bentonite clays, with "high shrink and swell potential" as reported by Rip White, deserve careful consideration as a landfill liner judging from their reputation as a road base. This application discusses "hot loads (i.e. ash or coals) in the section on fire protection. Isn't a special permit required to take such a category of refuse? .. g---Q,- a . Il sun ��' • 4. \- POPULATION DISTRIBUTION '?-''N re- l . . . - . 3`� i • Homes in landfill areas / . . ' .: '` ' I -25 _ _. __ c. 1 4.•�•• • Existing landfills �. •••• .wm / .._ • . Homes in kv Proposed landfills this area -. Y• • not • count' \ ,. , • S • 4+ • • ' • 9 �\ ` ;? ! Q. •1} -s:�, .v .._ 1 mile �f •.c- �- 1• ;\ i : . .` -, I6 Proposed I 5Nauanal i� '�`Y`.4 ; ,, � \ . Cement/ a t. I, ER 1E •• , Re,. - \ � \ . Asphalt _ � - . y -,i•• �) Tie , c��•.,� ( r- / 1 Spis (j r � • Recye l Lng ' .. . .s �� .lip w N... Horst A = I -1/,, L.19 • It\V\ � , �` norSt 8 •- • • - a. ',% s • 22 l • • r Erie _ • :j • .;-€! _, , s= ►- andfitl ••= ••1 : •�--• '' `- �- -I • • . � --L is �`�`"'( e`i_ , • .I� •� } l� I — . l , ,c . -~ � � S' N • Ins, - 27 . �I . • y-.7 `Zigan ��_ _ `p col umbine -vie.. 1 l �andfii! el ? - Recycling. M a' _ �i ( t I ,� ERIE' . . I .� ��- ;y ,y . Y ( 'G-f O • Jr. i, e„. W -B eY Ww%;Is Rasta _ R6}'W Jnl / eJ u „� II",i • i '^ /� mlf /l' • 0 of • .. ail / �l sy 1 / H 0O I ,• • • U IQit ` V• .. • f i# t e „ y w • I • • j • M I ri u>") ,` ` • • aM r • lINIH \`I I/ Kp i \tail d/t'11,2o 1 r o o. 1 '• / / \ ' D D I 1 / N I D a. � If li u I I I D Yfe r•/ _ �I ./ / ' '� / �� _�__�—Weald County _ -, l .•• l / /- Adams County ., D , / / • 1 \" D U r r,I K� %/////y��. i ' / T ``ea `• 1 Rm ��// / Kit / 1 ..--- '• 9 CO Renlder County _ -•-•• I 1--- Jeff County 1 kTdd U U D �\ `.` D I i Z / Si t vcCli w\ ( Io \A's _ NTda ' J • ♦ '• Figure 1. Tectonic and geologic sap of study area.. Seismic faults are shown by heavy lines: light lines are major surface faults or faults found in mines. B indicates basement faults. Symbols are shown on figure 2. 281 01rr'? 6.r May 17, 1991 7b: Weld County Planning S Zoning Commissioners Re: Proposed S.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention same of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Blowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -2asightliness of operation near residences -Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmtade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area bas better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted, frat Z 3 la , • ,e�� G� v G)! f t • Harding Lawmen Associates Table 1: Summary of Traffic Survey Unloaded Loaded Vehicles Vehicle 'Noe Weight (tbs) Weight (Ibsl Per Day Front-Load Collection Truck 32,000 54,000 44 Rear-Load Collection Truck 29,000 54,000 149 Roll-Off Containers 21,000 54,000 34 Transfer Trucks (tractor-trailer) 40,000 80,000 67 End-Dump Trucics NA NA 4 Can NA NA 5 Pick-Up Trucks NA NA 52 Miscellaneous NA NA 2,1 Total 428 • Notes: 1. Survey conducted on July 12, 1989 from 3:00 a.m. to 9:00 p.m. 2. Miscellaneous vehicles include vans, cars with trailers etc 3. Weights are approximate 4. NA - data not available F1 into) May 17, 1991 TO: Weld County Planning S Zoning Commissioners Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Blowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences -Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to reca m end denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted, 1.30 1c. �� 471- EXHIBIT 4 �a ��i,6 ax - l- May 17, 1991 7b: Weld County Planning S Zoning Commissioners Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling Virility and bring to your attention some of our concerns. We had hoped to see an std to the landfills in this area which are causing - -Increasing dangerous truck traffic an all surrounding roads in the area -Blowing trash frau site on hill -Lights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences -Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle ,Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage -it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted, JD 74 464 . ��2Sr �, J 0 Z ++2_ — C)0 -Veld ■ EXHIBIT May 17, 1991 To: Weld County Planning & Zoning Commissioners Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We mould like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Blowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangeripg pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Egyw Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. O S • Respectfully submitted, O � 4t-1/4- • ` 3a7, - ll `'9 f.,` a9 EXHIBIT �, se el May 17, 1991 To: Weld County Planning S Zoning Commissioners Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Blowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences Air pollution - small quantities emitted with methane gas Hater contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Maxmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the prornah . Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted, 411,2-.3 66c_g_- Fi1.; ✓-C�o eos7 6 EXHIBIT g2{fi= 33lo $ 77o • i el � `4 May 17, 1991 TO: Weld County Planning b Zoning Commissioners Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Blowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences -Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted, (117 .4e"t 13 z ei Gv . de/f.. .te 7- • EXHIBIT d�h ‘,//27- at-4- el /art, May 17, 1991 To: Weld County Planning S Zoning Com essicaers Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic an all surrounding roads in the area 17 -Blowing trash from site on hill '''' -Lights from equipment operated :✓ -Noise from equipment operated ✓ -Unsightliness of operation near residences ✓ m tespitIWW oUF teSi��&.- -Air pollution - small quantities emitted with e " Al -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for '!bran and County taxes✓ -Decreased property values for individuals s -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks ' -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and reisons ential lifestyleWind ve(ocz upo 4.0 - loo Miles expu ioq24.44 -lieu? w S.EMany of these problems constitute substantifor the Planning Commissioners to reco®end denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The lbwn of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents! The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact an the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted, ie Fla rtuuzri -etiz- Gue vi Het et- ifz9- 16C Z 1 (CpS- ifola-- + EXHIBIT .7.2: �--- 42ialliej _.t'. May 17, 1991 To: Weld County Planning b Zoning Commissioners Re: Proposed E.R.D. landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area Blowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences Air pollution - small quantities emitted with methane gas Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and ve feel our burden has been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted, , ' /a2Q_ 11:36 Wee /.3 1104 it "Hiatt' 49 May 17, 1991 TO: Weld County Planning & Zoning Commissioners Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention same of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Slowing trash from site on hill -Lights from equipment operated -Noise from equipment operated Ubsightli.ness of operation near residences -Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Tbwn and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage- it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted, '56f- /) c26- 5 O / 25- a41-�- May 17, 1991 To: weld County Planning b Zoning Commissioners issioners Re: Proposed E.R.D. Landfill in Southwestern weld County, Colorado WO would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention sauce of our concerns. we had toped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Blowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences -Air pollution - small quantities emitted with methane gas -water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Maumiade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just weld County, as you well knot, and we feel our burden has been borne. The facility in not needed for weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. we do not want to see this area continue to develop in this manner. we are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted,a ExHisti. , 109 Saut'', L7 � o, May 17, 1991 To: Weld County Planning 6 Zoning Commissioners Re: Proposed E.R.D. Landfill is Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Blowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences -Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for lawn and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitt Dzot4; 3 yo Wzra e 9e .203 LIR Jeri ems, G p.r/6 anis" el 0C11 • F 76 May 17, 1991 To: Weld County Planning & Zoning Commissioners Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We mould like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Blowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences -Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impnct on the use of the land. Thank you for your consideration. Respectfully submitted, Q]�V /P7P-6-7r Jl7�wlvLtiG^,G./ w /(� # 7 iJ!J"n f 0 . go / 4 J EXHIBIT • t �-rcd�sc May 17, 1991 To: Weld County Planning S Zoning Commissioners Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Slowing trash from site on hill -Lights from equipment operated -Noise from equipment operated -Dnsightliness of operation near residences Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban .Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted, �6e'r- /3 8° Quo ,J4- T,Eet- Sj 2< e r CO SOS-/ EXHIBIT �ro,a�^ !�w e fT A Ark May 17, 1991 TO: Weld County Planning S Zoning Commissioners Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which are causing - -Increasing dangerous truck traffic on all surrounding roads in the area -Blowing trash from site on hill bights from equipment operated -Noise from equipment operated -Unsightliness of operation near residences Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Legs of quality of life - rural lifestyle and residential lifestyle Many of these problems constitute substantive reasons for the Planning Commissioners to recommend denial of the proposal. Ranch Eggs Estates and Leisure Living subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden bas been borne. The facility in not needed for Weld County residents. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land. Thank you for your consideration. Respectfully submitted, Car fizL tr 1 S EXHIBIT TiCt,424') P43, 1 T lW'iel 2380 S. Cessna Dr. , Erie Airpark, Erie, Colo, 80516, May 21 , 1991 . Weld County Planning and Zoning Commission: Dear Sirs and Madams: We wish to go on record that we are vehemently opposed to locating the ZIGAN LANDFILL in our area. Our land and home values have been very low for a long time and are finally on an upswing, with positive growth in our area. (lot sales, new home starts, etc. ) If another dumpsite is situated this close to the residential area, our area will be known as the "DUMP CAPITAL of WELD COUNTY" , and home and land values will again plummet. As homeowners we cannot afford to have this happen! Yours truly, t SEcR,0,4te /l roeiwn.e rS Pat and Dan Montgomery r C 1. 1 SOUTHERN WELD COUNTY LANDFILLS w.c. 1 d �1� ' w.c. 1a ,o� ■ Medical s, Waste Purifier W.C. 12 is (BFI) U in W. 0 m >••••■ co in n r n� a) N N tz'-i 3 3 U 0 0 U U U ■ 3 �3 •C.B 3 3 3 3 Z' Horst Dacono (Westem Waste) 0■ Erie i f I W.C. 6 v '(Laidlaw) G a rl � Z9� 't � Lochbuie W■ tiling W.C.4 G Construction O' Northglenn Landfill J■ (Waste Management) Z W. . 2 ■ ■ ■ ■ ■ AVE. O — m;• 'W-470" 160TH AVE. HWY.7 • • AD MS OUN I 0 _� 152ND AVE. Q "O "•' 144TH AVE. = m �FOF lb ■ c C z co Ed 136TH AVE. . i ■ 3J a �- a O 3 128TH AVE. EXISTING AND PROPOSED LANDFILLS EXISTING LANDFILL ' EXHIBIT I NORTH III PROPOSED LANDFILL III �2 r South Weld Against Trash �� 1�. .n.' '. Community Awareness Meeting 7 p.m. April 12 Howard's Barn Agenda I. Welcome II. Introductions III. Overview of the landfill situation in Southem Weld County IV. 1. What is SWAT? 2. The SWAT mission V. Speakers 1. Weld County Commissioner Bill Webster 2. State Rep. Faye Fleming 3. State Sen. Jim Roberts 4. State Rep. William Jerke VI. Question and answer session VII. Conclusion/Summary VIII. Adjournment- Qf f fat"(l f) ci t:lc ��\ •� ' 1 l _- i-_q'7 r J 0 , .fie ,I i'ir !py • k • 1•. �.ahM.L. •li I,. ,..,lJ fir• ` 0 ��,._ra o t II -----11-7". „� � .� .•�•' - ! r >` i F v1. n'i\ —� - ,� 1 ., •Ija•IS.". n i ' ; 'r. _CELL ,� \'fit-�"� „ "� ,._c.S 44 t ; . • ` .. IL‘r : _ ..y.�- / Sri �hI• ,.E ' n Gf ri se....„..t: ,,... _ :tririr.".!tH" -47------J1 .."--\-- c:\ — •••• I :. O1 :, . Jr... •C.--.1 nua:"J ' i.•I -, ) I ",g, ), % � J I ��. _ ��N —.1 f• 1•p, I / C. 1 / 1l .. ,_ . . �; "Celt 1 \1 , . .. .... I I• I `` ' l o • .� ..... I WED Illa MAP �• .."1/4. . eorby4vM/� , � - ..e, -- *-RnMI •.w[ use ! k t — 'M 17 /:R, ..''fT'ti /, _C,[.' ;r •�. ;R.I r.T"'. . - /.I 1 -._ '_ _'F _r--.t-: • K ' t --• -- H AZ.,: ~ OT 5 i � CTE ENV S ` 116 .:= i.o.^hei: Weekly news and resources ft: c:..]ets firting tonics -- e:.lc^. IL, IF.. • vices concludes that this ideal permeability ANALYZING WHY ALL LANDFILLS LEAK is often not ved for a variety of reasons. (See pgse 3-3 through 3-8; case The U. S . Environmental Protection studies of clay liners appear in Appendix Agency (EPA) has paid for a series of A.) Therefore, they assume that the actual engineering studies to find out the best permeability in the real world lies between way to make a landfill. They wanted to 10-7 and 10-6 cm/s. Geoservices concludes, know what was the "best demonstrated "Possiblythe most significantobservation is available technology" (BDAT) for making that with compacted [clay] soil bottom landfills. These studies reach some liners, leakage out of the [landfill] will be surprising conclusions. large (if there is leakage through the top Landfills are bathtubs in the ground; liner). . .. even in [landfills] meeting cur- the bottom of the bathtub is called a liner rent EPA design requirements" including and it can be made of compacted clay soil, permeability of 10-7 cm/s (pg. 3-18) . BY or it can be made of a huge sheet of "large" leakage, Geoservices means 90 plastic underlain by ordinary soil, or it can gallons of fluid leaking through each acre be a huge sheet of plastic underlain by a each day, or 900 gallons per day leaking layer of compacted soil (usually clay soil) . from a 10-acre landfill. Their calculations The third combination, plastic liner and show that, with 3 inches of water standing compacted soil, is called a "composite on the bottom liner, it will take 15 years liner." (A composite liner is not a double for leakage to break through a 3-foot-thick liner; it is a single liner made up of two compacted clay bottom liner, but once parts; to create a double liner, you would breakthrough has occurred, 90 gallons per use two composite soil liners together, acre per day will pass through the liner separated by a layer of sand or gravel.) continuouslythereafter. (See pg. 3-16, and Geoservices did not examine the second Table 3-3 on pg. 3-40.) It won't take very type of liner (plastic sheet on ordinary soil) long to contaminate a large drinking water becauseordinary soil provides poor support supply if you pour 90 to 900 gallons of for a plastic liner carrying many tons of toxics into it day after day, year after weight, so they restricted their analysis to year. Thus Geoservices has shown that compacted clay liners vs. composite liners. clay liners are an environmental disaster. The EPA wanted to know which liners • Composite liners were the best ones available: compacted Geoservices reports that all plastic clay liners, or composite soil liners? So liners (also called Flexible Membrane they hired Geoservices (ofBoyton, Florida) Liners, or FMLs) always have some leaks. to tell them. The resulting study makes "A common misconception regarding FMLs is dull reading because it is filled with that they are impermeable, that is, no fluid technical details, but the conclusions are will pass through an intact FML. However, fascinating. All liners perform worse than it is important to realize that all materials anyone suspected. used as liners are at least slightly Clay liners . permeable to liquids or gases and a certain Geoservices didn't have much good to amount of permeation through liners should say about clay liners. The flow of liquids be expected. Additional leakage results through a liner (the liner's permeability) is from defects such as cracks, holes, and measured in centimeters per second (cm/s). faulty seams." (pg. 4 The EPA's current requirement for a liner FMLs often develop defects called for a hazardous waste landfill is that it "pinholes" during manufacture; these re- pass liquids through it no faster than 10-1 sultfrom thin places ("fish eyes"), bubbles, ®cm/s (read ten to the minus seven centi- foreign material, or lumps of carbon in the meters per second, or one ten millionth of raw molten plastic from which the FML is a centimeter per second). However, based rolled ("calendered") into sheets. Further- on actual experience in the field, Geoser more, when a large landfill liner is created EXHIBIT 7. .in glninc st-.rn of "::.•.: ti: ..e- wit.. - -- OUT NCH -_ ;UIC v.:. ..FF -- - .‘-.- ital... Geose-o:=es c-C'. .Cee some ..^.eta cri cork•....-.s am., ieF5 ce.t "- typical seam ce•ec: rates. The). loot. at s;a ootimustic: ..cncItions . +'.!p zt,ric:u::e . :•,- s. =-t.nruB-11) . Based on 9-41lthatthe -bestcempnstratedavaiiadie case studies i. S _ the six case studies, they draw the foi- technology (B✓AT) for composite lank'Ilt lowing -tentative conclusions:" an averaoe liners will allow leakace rates somek.nere of one leak per 30 feet of seam can be between 0.02 and 1 .0 gallons per acre per expected if there is no quality assurance day. (See Table B-10 on pg. B-51 . ) Thus program (quality assurance being a third they conclude that a 10-acre landfill will party coming along behind with special have a leak rate somewhere between 0.2 equipment to check the adequacy of the and 10 gallons per day, or between 73 and seams) . Even with good quality assurance, 3650 gallons of fluid per year; over 10 an average of one leak per 1000 feet of years, such a landfill will allow the leaking seam can be expected with reasonably good of 730 to 36,500 gallons of fluid. And this installation, adequate quality assurance, is the"best demonstrated available technol- and repair of noted defects." (pg. B-11) ogy"--the very best we can do when That is to szy, under the best of circum- . everything goes right. stances, you'll get one leak per thousand T_ Next week we will show that leaking feet of seam. If the landfill liner is made 730 to 36,500 gallons of toxics into a water by welding strips of FML that are each 20 supply during a 10-year period guarantees to 30 feet wide, you can expect one to two destruction of the drinking water resource. • defective seams in each acre of landfill. We will also show that the Geoservices .. Based on actual data, Geoservices study is unduly optimistic because, as they concludes that a "standard" (typical) leak in say themselves (pc. B-7), "Many types of an 'FML has an area of one square cen- FMLs swell when placed in contact with timeter (1/16 of a square inch) and that chemicals. As a result, the distance the"standard" (averaee) number is one hole between polymeric chains increases and per acre. They point out that this permeability increases. Therefore, an Frv'IL "standard" hole size and standard number can have a low permeability for water and per acre are based on the assumption that a high permeability for some chemicals. " "intensive quality assurance monitoring" will be performed during liner installation, if you're interested in technical details, so clearly we are talking about the best get: Geoservices, Inc. Backaround Docu- case, not the worst case here. Design ment on Bottom Liner Performance in Doc:- flaws, poor construction practice, or poor ble-Lined Landfills and Surface Impound- quality assurance would result in larger ments. Springfield, VA:NationalTechnical holes, greater numbers of holes, or even Information Service, April, 1987. Order laroe tears. (pg. B-13) from National Technical Information Ser- Geoservices then goes throuch an vice, Springfield, VA 12161; phone (703) elaborate mathematical analysis to figure 487-4650. OrderNo. PS87-18219-1. $36.95. Rachel's Hazardous Haste News is published weekly by Environmental Research Foundation. P.O. Box -3541. Princeton. NJ 08543. The Foundation is non-profits contributions are tax-deductible. Editor. Peter Monta- gue. Ph.D.; Associate Editor. Maria B. Pell 1 Assistant Editor. Annette Eubank; Hest Coast Editor. Tim Montague. The News is mailed first class every Tuesday. Subscription' $18 per year for individuals and non-profits. $6 for students and senior citizens. $150 for businesses. In Canada. add 54.001 in Europe. add $11.00. SUBSCRIPTION ORDER FORM Environmental Research Foundation FITS-CLASS MAIL P.O. Box 3541 U.S. POSTAGE Princeton. R., 08543-3541 PAID Name. Princeton. NJ FIRST CLASS MAIL RETURN REQUESTED Permit No. 434 Address. •. TO. f Complimentary - Dr. Stephen Lester City. Citizens Clearinghouse -- CCM.: P.O. Box 926 State and zip. Arlington. VA 22216 S1 Rp X11 - s _EXHIBIT cr -.-;g4 t . SICAN GUSTAVSON ASSOCIATES G E O L O G I STS • E N G I N E E R S February 12, 1991 Donald and Marylyn Brand, Chairpersons Concerned Citizens of Erie 8897 Baseline Road Lafayette, Colorado 80026 Dear Donald and Marylyn: Gustayson Associates, Inc. has been authorized by Concerned Citizens of Erie to conduct this study for the purpose of providing a geologic review of the soundness of the proposed Environmental Recycling and Disposal Co. (ERD)landfill,particularly in view of its location within a densely faulted area. We have further been advised that the report will be used by the Client at public hearings, to which we give our consent. Likewise, should this case proceed into litigation, we herewith give our permission for the use of our report in such litigation, and also express our willingness to provide expert testimony, if so requested. Gustayson Associates, Inc., as represented by its principal, Mr.John B. Gustayson, Certified Professional Geologist #2637, fulfills the requirement of"professional geologist" as defined in the statutes of the State of Colorado. Mr. Gustayson's certification is by the American Institute of Professional Geologists. The opinion provided herein is independent inasmuch as Gustayson Associates, Inc. and its principal, Mr.John B. Gustayson, are fully independent and hold no financial interest, either directly or indirectly, in Concemed Citizens of Erie, the properties being examined, or any properties in the vicinity of the proposed landfill. A number of professional publications as well as published data have been used in the examination of this property. They are listed in the following, "References Used" attachment. The publications have been found to be readily available, mostly from the Colorado Geological Survey,or in repositories thereof,such as the libraries of the University of Colorado and the Colorado School of Mines. The data is neither very new nor obscure; therefore, any prudent geologist can readily gain access to exactly the same data which formed the basis of our opinion. S757 Central Ave. Suite D Boulder. Co. 80301 ,303µa3-2209 Fax (303)443.3156 Telex 510100840t 1 008402 -2- This Consultant has examined available data from the public literature and studied the pans of the report relating to the geology of the proposed landfill site which was prepared for ERD by Kip R. White. We have subsequently formed an opinion which is as follows: The region about which the proposed ERD landfill is located within a region where faults or rock fractures exist. It is highly possible that faults or!factures exist in the proposed ERD landfill area which have not yet been discovered or mapped. In addition,the area is within a seismically active region where earthquakes have been experienced which could cause displacement of faults or fractures. Displacement of any faults which may exist in the proposed landfill area could cause failure of the disposal site liner. A number of groundwater areas currently exist in the proposed site area and,according to the excavation plan, will be exposed prior to the emplacement of the lining of the landfill. Failure of the liner could subsequently cause contamination of groundwater (of the Laramie/Fox Hills aquifer). Our opinion is based on a number of facts, each of which will be summarized below. Our first premise is that the area of the proposed landfill is within a densely faulted region which has been referred to in the literature as the Boulder-Weld fault zone (Davis and Weimer, 1976). A map of the area is enclosed with this letter. The proposed landfill area is geologically characterized by regional and local, structural features which trend in a northeasterly direction. These features include faults, folds and blocks. Faults in this region consist of three types; basement, growth and antithetic (Davis and Weimer, 1976). All of these faults may extend up to 3 to 4 thousand feet or more into the subsurface and are sometimes expressed or exposed at the surface. Two very deep basement faults which are seismically active exist in the region. The northeast trending Valmont fault, discovered in 1957, is approximately seven miles west of the proposed site. This fault is not expressed at the surface but is now exposed along a road cut on 75th Street (Kirkham, 1981). The southeast trending Rocky Mountain Arsenal fault is located approximately three and one half miles south of the proposed site. In 1962, a series of earthquakes which continued for years occurred along the Rocky Mountain Arsenal fault and its related fracture zone (Kirkham, 1981). The fact that this fault has been active recently suggests that rock stresses which extend from the basement exist in the area. Such stresses are relieved through earthquakes which can effect fractures, faults or weaknesses in the bedrock or substratum. Anomalous geomorphic features within the area of Rocky Mountain Arsenal fault also indicate Quaternary fault activity (Kirkham, 1981). Many other earthquakes have been experienced in the region northeast of Denver and in particular within an area surrounding the proposed landfill. Over 200 earthquakes of up to 5.3 mb (mb or bodywave magnitude as defined by Gutenberg and Richter, 1956) have been centered in an area northeast of Denver (Kirkham, 1985). An area just east of Lafayette, Colorado has felt earthquakes with a modified Mercalli intensity of up to VII (Kirkham, 1981). This intensity is defined by the American Geological Institute as: �' fi c-,1 -3- "difficult to stand...noticed by drivers...furniture broken...damage to masonry, including cracks...fall of loose bricks, stones, tiles...concrete irrigation ditches damaged..small slides and caving along gravel banks" (Dietrich et al., 1982). The region where the proposed site is to be located is a densely faulted and fractured area. A number of small southeast to east trending faults intersect the main northeast trending faults. This kind of fault or fracture pattem is commonly associated with coupled rock stresses (Billings, 1972). Therefore some of the normal faults in this area are likely to have been caused by basement stress or mild tectonic activity (earthquakes) in contrast to the numerous non-tectonic mechanisms responsible for the growth faults which exist in the area. The fault density of the Boulder-Weld fault zone is in the range of 2 to S faults per mile (measured perpendicular to the main northeast fault trend pattern as shown on the enclosed map). The faults mapped in the immediate vicinity of the proposed landfill have density of about 2 or 3 per mile. These faults are mapped with certainty (that is they are exposed and/or expressed at the surface) everywhere the Cretaceous age Laramie Formation outcrops. Laramie outcrops are found mostly to the west and southwest of the proposed landfill. Where the Laramie is covered by unconsolidated Quaternary deposits, the faults are mapped as being "concealed". Concealed faults are known to exist from surface anomalies, trends, or seismic or borehole data. Because most of the proposed site is covered by unconsolidated Quaternary deposits, any faults that exist in the area would be concealed, or not expressed at the surface and therefore could not be mapped without subsurface data. Davis and Weimer (1976) studied much of the Boulder-Weld fault zone with seismic data but they had no such data for the south half of Township 1 north, Range 68 west which encompasses the proposed landfill area. Any statement or claim to the effect that faults absolutely do not exist in the proposed area could be false. Such a statement based on regional evidence is made accurate by the qualification that "none have been mapped, they may or may not exist". Actually a few faults do exist in Section 28, one of which trends to the northeast and apparently dies out about 100 feet to the southeast of borehole 38 (refer to Plate 1, Kip White, 1990). Since many of the northeast trending faults extend for miles, it is not inconceivable that this fault could continue further beneath deposits which conceal it. This particular fault, a splay off a major growth fault, (controlling fault for previously mined coal deposits to the west) may continue along a direct northeast trend through the proposed landfill where it could join with a mapped "concealed" fault present in section 22 (see enclosed map). Another fault is mapped in the southeast part of section 28 which continues, concealed, for several miles to the northeast. The second premise to be discussed is the presence of shallow or perched groundwater in areas which are faulted. Groundwater is of extreme importance here because it moves or migrates in the bedrock or in aquifers, rising and falling with the annual cycles of rain and el 4ri w -4- snowfall, as well as being forced laterally along the piezometric gradient. Consequently, should waste fluids from the landfill mix with the groundwater in the area it could contaminate the Laramie/Fox Hills aquifer. White (1990) states that the two prominent northeast trending faults which more or less border the proposed site act as barriers to groundwater movement within the proposed landfill area. 'Ibis may be true in a horizontal or perpendicular direction to the faults,but faults and even more so fractures are known to act as groundwater conduits. Groundwater could enter a fault plane or fracture zone and travel along that zone until it reacher permeable bed or the surface. Six ground water areas have been mapped areas by White (1990), see enclosure. Five of the six areas either are cut by faults or are within 250 feet of a fault. Groundwater area 1 which apparently was not studied outside of section 28 to the northwest is very close to where two faults are mapped. The only groundwater area which has not been associated with a fault is area number 2. Groundwater area number 2 is also completely covered by unconsolidated Quaternary deposits which often conceal faults. Evidence that faults may act as a conduit is found in the center of section 29, one half mile to the west of the proposed site. A surface spring exists at this location which is intersected by a northeast trending fault. Anomalous groundwater samples have been taken in the area of the proposed landfill. Samples taken at boreholes number 1,11,19 and 20 have anomalously high concentrations of total organic carbon (TOC) and dissolved manganese. Sample 4 and 15 also show increased levels of manganese (see enclosed map). Such concentrations might occur in water sources deep in the ground and/or water that has migrated along fault planes. The high concentrations of organic carbon and manganese may suggest that the groundwater is sourced from an oxygen poor or reducing environment (coal seams). These particular elements are commonly biodegraded (as in organic carbon) or oxidized (as in manganese). It is noted that borehole 1,4,19 and 20 occur near mapped faults. The anomalous groundwater sample at borehole 11 is in an area where no faults have been mapped (an area where unconsolidated Quaternary deposits exist at the surface). It is therefore possible that the groundwater in sample 11 may have migrated from a deep source along a fault plane or fracture zone which has not been mapped. Topographic features and anomalies such as lineaments, drainage patterns, escarpments and ridges are used by geologists and geomorphologists as evidence of faults and fractures. The drainage patterns in the vicinity of the proposed landfill site generally trend northeast and northwest, the same trends exhibited by the faults in the area. Strong northeast trending drainage patterns exist in the north and northeast parts of the proposed site. Drainage areas which exhibit the same trends, southwest of the proposed site, are often close to or parallel mapped faults. The proposed landfill excavation will strip off most, if not all, of the unconsolidated Quaternary deposits. It will also excavate below the groundwater level in area number 3 in the center of the proposed site. The likelihood that these groundwater areas and -5- potential aquifers will be breached by the excavation is good. The potential for groundwater contamination would increase should faults be discovered below the unconsolidated Quaternary deposits. Because this area is a topographic "high" runoff contamination is also likely should the landfill liner be breached by fault movement or earthquakes. Finally as stated by White (1990) the time of travel from boreholes 19 and 20 to the nearest residence is only 183 years. Boreholes 19 and 20 are within 250 feet of a mapped fault The published literature, reports and maps point to the fact that the proposed ERD landfill site is located in a densely faulted and earthquake prone region. Although geologic maps show few, if any, faults within the proposed site boundary, evidence suggests that faults might exist which have not yet been discovered. It is therefore the opinion of this Consultant that considerable research and field studies should be performed which would undeniably confirm the absence of and/or fractures at the proposed site. However the area's propensity for earthquakes may preclude such research since any recent or future tectonic activity could result in bedrock or substratum failure, rendering the proposed site an environmental hazard to groundwater and nearby residences. Sincerely, GUSTA ASSO S, INC. '' R. 4;,,, ♦Lat w i p�1- ?t:� C�,4% B. Gu son, President ₹ma y' b` t cl `-=- ertified Pr: 'essional Geologist #2637 ' � '� f Enclosures ✓Hp�B. GUSZe • REFERENCES USED Billings, M.P., 1972, Structural geology, third edition: Prentice-Hall, Inc., New Jersey, 606 p. Colorado State Government, 1989,Solid wastes disposal sites and facilities:Colorado Revised Statues, C.R.S. 30-20-101-112. Colton, RB., and ILL. Lowrie, 1973, Map showing mined areas of the Boulder-Weld Coalfield, Colorado: U.S. Geological Survey Map MF-513. and L.W. Anderson, 1977, Preliminary geologic map of the Erie Quadrangle, Boulder, Weld and Adams Counties, Colorado: U.S. Geological Survey Map MF-882. , 1978, Geologic map of the Boulder-Fort Collins-Greeley area, Colorado: U.S. Geological Survey Map I-855-G. Davis, T.L, and R.J. Weimer, 1976, Late Cretaceous growth faulting, Denver basin, Colorado: in Professional Contributions of the Colorado School of Mines, Studies in Field Geology, v. 8, p. 280-300. Davis,T.L, 1985, Seismic evidence of tectonic influence on development of Cretaceous listric normal faults, Boulder-Wattenberg-Greeley area, Denver Basin Colorado: in The Mountain Geologist, Rocky Mountain Association of Geologists, v. 22, n. 2, p. 47-54. Dietrich, R.V. et al., 1982, AGI data sheets, for geology in the field, laboratory and, office: American Geological Institute, 61 p. Environmental Protection Agency, 1988, 40 CFR Parts 257 and 258 - Solid waste disposal facility criteria: Federal Register v. 53, n. 168, p. 33314-33316, 33332-33335. Goldfarb, W., 1981, Three important court decisions: Water Resources Bulletin, v. 17, n. 6, p. 1097-1098. Kirkham,R.M. and William P.Rogers, 1981,Earthquake potential in Colorado,a preliminary evaluation: Colorado Geological Survey,Department of Natural Resources Bulletin n.43, 171 p. Kirkham, R.M. and William P. Rogers, 1985, Colorado earthquake data and interpretations, 1867 to 1965: Colorado Geological Survey, Department of Natural Resources Bulletin n. 46, 106 p. tri” �� • Rogers, W.P, LR. Ladwig, A.L.Hornbalter, S.D. Schwochow, S.S. Hart, D.C. Shelton, D.L. Scroggs,and J.M.Soule,1974,Guidelines and criteria for identification of geologic hazard and mineral resource areas: Colorado Geological Survey, Special Publication n. 6. White, K R., 1990, Landfill design, operation, and closure plan for the proposed Environmental Recycling and Disposal .Co. facility in.southwestern Weld County, Colorado: Project No. 8912-04, 82 p. White,K R, 1990, Plates 1 through 8 for Landfill design, operation, and closure plan for the proposed Environmental Recycling and Disposal Co. facility in southwestern Weld County, Colorado: Project No. 8912-04. Tweto, O, 1976, Preli,ninaty geologic map of Colorado: U.S. Geological Survey Miscellaneous Feld Studies Map MF-788. R 6) • ai )•-__?.1)i'.i. �� z J'. o 'i .\ u t � ��__ _rte- -. _ �� / Ty oz-. • ,,,Al ' 19 - - �-( '' /y I ' do ,-.•_•!. .. 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In �II•'', TX,+"' .wf S-i?1`r. 5ti • ?!tt 107427 •0 NER11 OVENTNCR • • , r 3C 1 11eT 27 000-CIS s . t d s ' 3 a;L'`al ice= • -, • 6• Q •— O • I • I1 i t . VIEW Om 1 • ii � 1{67-2{:0;e-00e�l(tI _• -l • .� " ` •. • - • • ► - - z . i I 1 - •• /// ••C I• • • / G 2 � I "4 - � f ' ' .� i . , 4 1 7' OM Rt0'10e L1L00R 1 R.NEST It — so • `33 �. lb Y , /pj ....- s .R ® i GUSTAVSON ASSOCIATES R. •R sR I7 1' .• 3737 Cana Ave Suite D Sauer.Co 110701 •g -;I p03µ4}2209 Fax(303µ4Y7156 T•es 310100032 1r,. — _ • I EXPLANATION \ I _ • . • ' -Area of proposed special use .R • � -Area of Cretaceous Laramie/Fox Hills Fm- outcrop , . •R - • • Q ea•Groundwater area and number (after White, 1990) / 3 4 • (tit Groundwater sample and borehole number I I• _••-Mapped fault, dotted where concealed I I I / ) i ��' _ ___ ==4 (after Colton E Anderson, 1977 and Colton, 1979) R\�\\ / 1 ` I- - -- i � - Dralnage:perennial and Intermittent \ 1 + J\ ^�\ Tacodashed where inferred from topography ----...i._ 3232 1 ` •; . \ -.,,f •� `� �I ' ) iw-- Base map reprinted from �"'-'"- � � �-'� • SPECIAL USE REPORT P!-ATE 1 • (White, p rep h0 ..S% ` . - Seale l" : 1000'I •'� (.2 •L. a Togo contour Interval 10. • IGIi AY 7 %t BM 2 7 Wi1�•-tGO?�'/ In i-k-N\ ) ) Mid-American 10O6 walnut Street P.O.Box 156 • Waste Systems, Inc. Canal Winchester, Onto 43110 Phone(814)833-9185 FAX(814)833-9173 May 8, 1991 Ms. Dorothy Shamy 3110 Johnstown Lane Erie, Colorado 80516 Dear Ms. Shamy: Please allow this letter to serve as confirmation that Mr. Timothy J. Salopek, President of Waste Placement Professionals, Inc. is a representative of Mid- American Waste Systems, Inc. in the Weld County Landfill Development Project, and is authorized to enter into negotiations on behalf of Mid-American Waste Systems, Inc on this project. A note concerning Ted Zigon's role. Ted has indicated to the Company that his role would be one of supporting the development of the landfill project until it is permitted and then would concentrate his efforts on the recycling side of this venture. It should be noted that Mid-American is responsible and in complete control of both operations. Sincerely, //// Christopher L. White President and Chief Executive Officer CLW:pm cc Timothy J. Salopek Waste Placement Professionals a EXHIBIT - gS Z-iV �,Printed on Recycled Paper n4 fin 4 41 X1^1"'A Fla THE FARMERS RESERVOIR & IRRIGAi ION CO. BO S.27TH AVENUE BRIGHTON,COLORADO BOOM J LETTER OF TRANSMITTAL C,T0: '2-0 (�� -QQA) � �\ VIA CARRIER: U) V-C1C NV\AJ\N (\ MAIL: X 1 OTHER: SUBJECT: E_ N; \ k v' e V\ \AL A\c.C;1, � zSAANC,1 ULS*OSC, 4 ea\-2_ (_,AA JOB NO. ORIGINAL \' PRINTS LETTER FOR YOUR INFORMATION AS REQUESTED FOR YOUR PROCESSING OTHER REMARKS: � 'G�yk �_ YN.) C C) -CJ \CC S \ \l\�UJ ?a c\cieC \ ‘sicAC ek �� C��wvvr\y; kax- csX Q\� v;\ OS v7. Y�ys dd C� � Y\G.\?-� C"�\11� %\\-si-�\�-�A:\N-i aC, \"ACT_) \cis \t, �c \\1\--st- • V SIGNED DATE COPIES T0: REPLY REQUESTED YES NO - .\ C t* r " JI, fl WELD COtli% t COMMISSIONERS May 23, 1991 1191 KAY 28 AM W 16 CLERK P.O. Box 643 j0 THE BOARD Erie, CO 80516 Weld County Commissioners P.O. Box 758 Greeley, CO 80632 Dear Commissioners: Enclosed please find for your perusal copies of various reports and letters related to the landfill situation in Erie. Note that the Concerned Citizens of Erie and Parkland Estates form the group known as S.E.E. (Safe Ecological Environment) Committee. Listed below are the documents that are enclosed. 1. Gustayson Associates' geological report delivered to the Colorado Department of Health on the downsized Horst Landfill application entitled "Review of the Proposed Horst Landfill" . 2. Shawn Mulligan's letter and exhibits (including the CDH denial of the original Horst application) . It was included in the packet delivered to CDH. 3. Gustayson Associates' geological report on Horst's 600 acre landfill application. 4. Gustayson Associates' geological report on the E.R.D. Facility (Zigan application) . 5. a portion of the CDH Preliminary Assessment of the Columbine Landfill (which includes areas of current Laidlaw North and Laidlaw South. 6. "Coal Mine Subsidence and Land Use in the Boulder-Weld Coalfield" by Amuedo and Ivey. Please note the highlighted notations. The E.R.D. Facility application uses some of this research and material to locate their facility's borders. We hope that you will take time to read through these documents for a better understanding of the geological hazards in the Erie area. All of these documents relate to your deliberations on the E.R.D. Facility application by Mr. Zigan. Thank you for your consideration. . Sincerely, S.E.E. Committee Board Members: Janice Whalen, chairperson Tom Konetski, vice-chairperson Dick Medenwaldt Marilyn Silver Phone Contact: Janice Whalen at 665-6870 5106/9 ce 1''��YLtrt-(s) STATE OF COLORADO COLORADO DEPARTMENT OF HEALTH oe•cow 0 A9 Telefax: (�r' d 4210 East 11th Avenue (303)322-9076(Main Building/Denver) Denver,Coldrado 80220-3716 (303)320-1529(Ptarmigan Place/Denver) *t ) **1 *lc 1 Phone (303) 320-8333 (303)248-7198(GrandJunction Regional Office) +1e 76+. Roy Romer Governor Thomas M.Vernon, M.D. May 17 , 1991 Executive Director Chuck Cunliffe, Director Weld County Planning & Zoning Office 915 10th street Greeley, Colorado 80631 Project: Solid Waste, ERD Inc. , Southern Weld County. Dear Mr. Cunliffe: I know that members of the Solid Waste staff in the Colorado Department of Health, Solid Waste program have prepared, documented and provided technical to you and the county commissioners their comments and concerns with regard to this facility; so I won't need not repeat these issues at this time. I would, however, at the request of Mr. Ted Zigan, like to take this opportunity to write to you concerning the potential benefits of the treatment and service included in the proposal for the ERD Inc. site and facility. As a concept, this Department supports the development of integrated solid waste systems and strategies. It is heartening to see proposals for new solid waste sites and facilities which include recycling, materials recovery and waste stream diversion mechanisms prior to final waste disposal. The advantages of increased flexibility in solid waste management systems is recognized by private industry. It is exciting to see sites proposed in Colorado to address this issue and to have site owners/managers with the forethought to include these elements in their initial application for a certificate of designation. The long term benefits of this type of diversification will be proven by the success and successful operation of facilities like the ERD proposal. rl aY 2 4 1991 •1114 for Piano ��i an r -,z On) , , Chuck Cunliffe, Weia County Planning May 17, 1991 Page 2 I hope that this site is one of many proposed for areas throughout the state that will provide alternatives to the landfilling-only concept of waste management. I also hope that existing sites will continue to upgrade and diversify that range of services to reflect the increased public demand for comprehensive waste management and waste minimization. Thank you for your efforts in this area. If there are any questions that you would like to address to me or my staff feel free to call at any time. inc ely, Pa�a��l�a le7, ChiciSit/ "-- Solid G Waste & Incident Managemen ection Hazardous Materials & Waste Ma gement Division el r,`,"161) , July 3, 1991 , -- To: Weld County Commissioners P.O. Box 758 Greeley, CO 80632 Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which will continue to cause - -Increasing dangerous truck traffic on all surrounding roads in the area -Damage to roads in the area -Blowing trash from site on hill and trash hauling trucks -Lights from equipment operated -Noise from equipment operated and truck traffic -Unsightliness of operation near residences -Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle (Area is within .11 mile of residential areas. ) Many of these problems constitute substantive reasons for the Commissioners to deny the proposal. In addition, a 24 hour operation with 100 employees would cause another disruption of residential lifestyles. Ranch Eggs Estates, Carol Heights and Leisure Living Subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. Broomfield is opposed to this development and has other plans for this area. They have zoned a residential section within a g mile. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents and certainly has questionable need for the entire metro area. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. Please fulfill your obligation to protect the citizens' interests in this area. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land and its citizens. Thank you for your consideration. Respectfully submitted, ,J € July 3, 1991 To: Weld County Commissioners P.O. Box 758 Greeley, CO 80632 Re: Proposed E.R.D. Landfill in Southwestern Weld County, Colorado We would like to voice our opposition to this proposed 200 acre landfill and recycling facility and bring to your attention some of our concerns. We had hoped to see an end to the landfills in this area which will continue to cause - -Increasing dangerous truck traffic on all surrounding roads in the area -Damage to roads in the area -Blowing trash from site on hill and trash hauling trucks -Lights from equipment operated -Noise from equipment operated and truck traffic -Unsightliness of operation near residences -Air pollution - small quantities emitted with methane gas -Water contamination likely, as shown by the old and current landfills nearby -Loss in potential Denver metro growth spinoff -Decreased property values for Town and County taxes -Decreased property values for individuals -Difficulty selling properties -Increased bird populations endangering pilots at two nearby airparks -Manmade mountains to obstruct views -Loss of quality of life - rural lifestyle and residential lifestyle (Area is within '/2 mile of residential areas. ) Many of these problems constitute substantive reasons for the Commissioners to deny the proposal. In addition, a 24 hour operation with 100 employees would cause another disruption of residential lifestyles. Ranch Eggs Estates, Carol Heights and Leisure Living Subdivision are residential developments and farms less than 1 mile from the development. The residential portions of Erie are slightly over a mile. The Town of Erie is opposed to the E.R.D. proposal and the proposal is definitely within Erie's Urban Growth Boundary. Broomfield is opposed to this development and has other plans for this area. They have zoned a residential section within a z mile. These landfills serve the entire metro area - not just Weld County, as you well know, and we feel our burden has been borne. The facility in not needed for Weld County residents and certainly has questionable need for the entire metro area. The area has better potential, too much population and valuable, hard-earned home values. One negative does not justify the next, but it does encourage it - just as positives can beget positives. We do not want to see this area continue to develop in this manner. Please fulfill your obligation to protect the citizens' interests in this area. We are sure you will all carefully deliberate a proposal with such tremendous current impact on the citizens and future impact on the use of the land and its citizens. Thank you for your consideration. Respectfully submitted, ,24,14.a �n� �j / � � OFFA �/ �/ie5 c-4 c, C G 5. �- 910613 E NVIRONMENTAL RECYCLING AND 2200 E. 104th Ave., Suite 214 Thornton, CO 80233 DISPOSAL, INC. 4573333 May 6. 1991 Mr. Rod Allison: Weld County Department of Planning Services 915 10th Street Greeley. Colorado 80631 Dear Mr. Allison: I 'm sure by this time you have seen much information on my proposed recycling and landfill project. Much more information will be forthcoming at our hearing on May 21 , 1991 . Indeed so much information that it may be confusing . Because of that I would like to offer some of this information now for your convenience. My recycling facility will be built at the landfill. All trucks that have recyclables on them will be directed to dump their loads inside of a large building. Inside this building the following items will be removed by mechanical and manual means : Plastics (HDPE and PET) , ferrous metal, aluminum, glass , newsprint, and cardboard. This will reduce the waste stream by 20-25%. This type of recycling is being done successfully in other parts of the country, one such facility is in Crestwood, Illinois , a suburb of Chicago. I toured this facility last November and I was very impressed. Enclosed is a video tape of this facility. While watching this tape please keep in mind that : 1 ) Illinois has a law prohibiting yard waste to be thrown out with normal trash: notice how much yard waste is still being thrown out. 2 ) Many communities that use this facility have active curbside recycling programs : notice how many recyclables still remain in the trash after curbside is done . Thank you for looking at this information and I will be looking forward to answering any questions you have at the Planning Commission Hearing. Sincerely, d�27" Ted Zigan President S ff1 1 TZ/gw E NVIRONMENTAL RECYCLING AND 2200 E. 104th Ave., Suite 214 Thornton, CO 80233 DISPOSAL, INC. 4573333 May 20 , 1991 iV.AY ? `' 199; Yield to.Plan► t 5Mataia� Weld County Department of Planning Services 915 10th Street Greeley, Colorado 80631 Attention : Rod Allison Subject : Case Number USR-925 , Environmental Recycling and Disposal , Inc . Reference : Memo from Wes Potter, Director of Environmental Protection Services , Weld County Dear Rod : In the referenced memo , Wes Potter states that Environmental Protection Services recommends approval of the USR-925 subject to 13 conditions which are outlined in the memo. Environmental Recycling and Disposal Inc . agrees to comply with the 13 conditions stated in the referenced memo. Sincerely, c ` Ted Ziga n , flesident cc . Kip R. White , KRW Consulting, Inc . TZ/gw Elisa M. Gaul Darrell D. and Frances L. Thomas 1474 Weld County Road 7 1574 Weld County Road 7 Erie, CO 80516 Eire, CO 80516 David J. Huber Environmental Recycling & Disposal Co 3172 Weld County Road 6 c/o Mr. Ted Zigan Erie, CO 80516 2200 East 104th Avenue #214B Thornton, CO 80233 Mary Baker 3423 Weld County Road 6 Erie, CO 80516 Swink Family Farms and Etals 2510 West 144th Avenue Broomfield, CO 80020 Daniel R. and Jacqueline S. Horst 2240 Weld County Road 5 Erie, CO 80516 Rocky Mountain Fuel Company 910 15th Street Denver, CO 80202 Cosslett Estate Etal. c/o Longmont National Bank 510 Coffman Longmont, CO 80501 Richard Cosslett, et al c/o Longmont National Bank 510 Coffman Longmont, CO 80501 Kenneth E. Pratt and Karen K. Landers P.O. Box 801 Longmont, CO 80501 Gordo acy, a'rman oa f Co ty Comm' sio ers W 1 o nt 9 1 th ree'reele CO 1 Stanley A. and Leone M. Zimmerman 16005 Inglewood Road, N.E. Bothell, WA 98011 Baseline Investment Company c/o Poole and Company 2201 Kipling Street Lakewood, CO 80215 Wilson W. and Lila R. West 2550 175th Avenue Erie, CO 80516 Energy Oil, Inc. c/o Snyder Oil Company 2500 First Republic Bank Tower Ft. Worth, TX 76102 Lothar c/o Herta Guenther 1424 Weld County Road 7 Erie, CO 80516 q P f2.l,.v:;F-1 s7 (�1CuQ�caQda• 7/a-7q i P tf tot 4; DEPARTMENT OF PLANNING SERVICES PHONE(303)356-4000,En.44O0 91510th STREET GREELEY,COLORADO 80631 II lige COLORADO April 15, 1991 Mr. Ted Zigan 2200 E. 104th Avenue, #214B Thornton, CO 80233 Subject: Request for a Site Specific Development Plan, Special Review Permit, and Certificate of Designation for an Environmental Recycling and Solid Waste Disposal Site and Facility located in the W2 of Section 28, T1N, R68W of the 6th P.M. , Weld County, Colorado. Dear Mr. Zigan: The Department of Planning Services' staff has scheduled a public meeting on May 21, 1991, at 1:30 p.m. , for consideration of the above referenced application. This meeting will take place in the County Commissioners' Hearing Room, First Floor, Weld County Centennial Center, 915 10th Street, Greeley, Colorado. It is recommended that you and/or a representative be in attendance to answer any questions the Planning Commission members might have with respect to your application. It is the responsibility of an applicant to see that a sign is posted on the property under consideration at least 10 days preceding the hearing date. Sometime prior to May 10, 1991, you or a representative should call me to obtain a sign to be posted on the site no later than May 11, 1991. The Department of Planning Services' staff will make a recommendation concerning this application to the Weld County Planning Commission. It is the responsibility of an applicant to call the Department of Planning Services' office a few days before the date of the Planning Commission hearing to obtain that recommendation. If you have any questions concerning this matter, please feel free to call me. Sincerely, Rod Allison Principal Planner pc: Mr. Larry Bertowitz, Esq. 1775 Sherman Street, Suite 1700 Denver, CO 80203 c) k.0� a • STATE OF COLORADO ) )s.s. COUNTY OF WELD ) David B. Reynolds, being duly sworn, says that he is publisher of . The New News, a weekly newspaper published in K burg in said County and State; that said newspaper has a NOTICE oP PUBLIC HEARING p 1 circulation in said County and has been continously and &matwill bold a uni optedly published therein, ai 1. �meythem y�'�d during a period of at least ' s°`, , - fifty-two consecutive weeks prior to �t�,PPtbea cute the first publication of the annexed below'. Aproeip°og°"t>x ropiest may ass • vested notice; that said newspaper is a 112=KtirtWmaard w newspaper within the meaning of the cAlfram: Enviseet,eng act of the General Assembly of the b R de State of Colorado,. entitled "An Act 98, TIN,°RIM a tbbee P •Weld Cam Corrado. to regulate the printing of legal erm >Nzr oP USE: A Site ' tc notices and advertisements," and Plaai� " amendments thereto; that the notice tlaooffor an on,bm e te of ntal disposal of which the annexed is a printed ate and�ta�mo,��In the A Copy taken from said newspaper, was nbe) Sa�m�Cof and to the Tows of Erie• published in said newspaper, and in oda of and adjacent to Weld Tollthe regular and entire issue ofe0,,a��comer Road S.� every number thereof, baring w0 b;be held ' tGmtamial HS once a week for __ street, °racy or objections cared to successive weeks; that said notice a ��ga,,m�� +bead be weki was so published in said newspaper 1°imen"7 a °$s"tam Shea. Room proper and not in any supplement cteeier,ve co;aado 99tj thereof, and that the first � pudic hearing m Near t21, publication of said notice as Mies of Ce application are he aforesaid, was on the the for public d °v"""" g=ym, Room s9t Web Coe2 SConfmoW Center 815 Tense day of , 19 1 1 e °> , Colorado �. Rider•Canning W be_published ed in Commission and the last on the DS day of �bfevm teeKKnrenB To be dal one (l) time br N The New News 197 April 25,1981. I 1/� • Subscribed and sworn to efore _ _� C , -, me this _,L day of hKcw , �1 ; IOC :-riI i i Ci 6 V n\, 19 p/ . iotrirtvor d e• rev—. gees co. Maw* Alumni. My Commission expires Marc`1 5,1992 r SURROUNDING PROPERTY OWNERS MINERALS AND/OR SUBSURFACE OWNERS Environmental Recycling and Disposal Co. , c/o Mr. Ted Zogan Richard Cosslett, et al. c/o Longmont National Bank 510 Coffman Longmont, CO 80501 Kenneth E. Pratt and Karen K. Landers P.O. Box 801 Longmont, CO 80501 Gordon Lacy, Chairman Board of County Commissioners, Weld County 915 10th Street Greeley, CO 80631 Stanley A. and Leone M. Zimmerman 16005 Inglewood Road, N.E. Bothell, WA 98011 Baseline Investment Company c/o Poole and Company 2201 Kipling Street Lakewood, CO 80215 Wilson W. and Lila R. West 2550 175th Avenue Erie, CO 80516 Energy Oil, Inc. c/o Snyder Oil Company 2500 First Republic Bank Tower Ft. Worth, TX 76102 Lothar c/o Herta Guenther 1424 Weld County Road 7 Erie, CO 80516 Darrell D. and Frances L. Thomas 1574 Weld County Road 7 Erie, CO 80516 1.1`11 Eliza M. Gaul 1474 Weld County Road 7 Erie, CO 80516 David J. Huber 3172 Weld County Road 6 Erie, CO 80516 Mary Baker 3423 Weld County Road 6 Erie, CO 80516 Swink Family Farms and Etals 2510 W. 144th Avenue Broomfield, CO 80020 Daniel R. and Jacqueline S. Horst 2240 Weld County Road 5 Erie, CO 80516 Rocky Mountan Fuel Company 910 15th Street Denver, CO 80202 Cosslett Estate Etal. c/o Longmont National Bank 510 Coffman Longmont, CO 80501 C (./51.1 • I A S.;;On (TI)Lal I 4 gi)cW) 7) • MAR 1 1991 Weld Th. Plan:tin Carratniat March 13, 1991 Mr.Rod Allison,Principal Planner Department of Planning Services Weld County 915 10th Street Greeley, Colorado 80631 Dear Mr. Allison: I received the addendum to the application from Environmental and Recycling Disposal Company for a Site Specific Development Plan and Use by Special Review for a sanitary landfill and recycling facility.We recommend denial of this request for a number of reasons.First, there are already a concentration of landfills in the Weld County area; three — out of the eight existing landfills in the Denver Metro Region are located in Weld County. Additionally, that concentration could increase substantially,regardless of the outcome of the request before you. Besides the Ric Thermal Medical Waste Incinerator that has been approved but is not yet operating, there are four proposed landfills located in Weld County that are pending statalocal approval (Horst A, Horst B,Northglenn, and Westem Waste). If all of these landfills were to begin operating in the near future, there would be more landfills (9) located in Weld County than in the rest of the Denver Metro Region Combined. Second, there is not an immediate need for new landfill facilities in our area. According to the State Health Department,existing landfill space is sufficient to serve the needs of the Denver Metro Region for the next 15 years. Finally,while much of Weld County could benefit from the development and growth associated with the proposed E-470 and the new International Airport,this opportunity will not materialize if it must compete with a multitude of landfills. • I hope you find this information useful. Please contact me at 538-7295 if you have any questions concerning our response. Sincerely, David Callahan,ASLA,AICP Planning and Development Manager cc: David Wenzel,Community Development Director cog k,(71 r o . GUSTAVSON ASSOCIATES G E O L O G I S T S • E N G I N E E R S March 28, 1990 Parkland Homeowners Association 1525 Rue de Trust Erie, Colorado 80516 Ladies and Gentlemen: Gustayson Associates, Inc. has been authorized by Parkland Homeowners Association to conduct this study for the purpose of providing a geologic review of the soundness of the proposed Horst landfill , particularly in view of its location over old coalmine workings. We have further been advised that the report will be used by the Client at public hearings, to which we give our consent. Likewise, should this case proceed into litigation, we herewith give our permission for the use of our report in such litigation, and also express our willingness to provide expert testimony, if so requested. Gustayson Associates, Inc. , as represented by its principal , Mr. John B. Gustayson, Certified Professional Geologist #2637, fulfills the requirement of "professional geologist" as defined in the statutes of the State of Colorado. Mr. Gustayson's certification is by the American Institute of Professional Geologists. . The opinion provided herein is independent inasmuch as Gustayson Associates, Inc. and its principal , Mr. John B. Gustayson, are fully independent and hold no financial interest, either directly or indirectly, in Parkland Homeowners Association, the properties being examined, or any properties in the neighborhood thereof. A large number of published data have been used in the examination of this property. They are shown in Enclosure 1 hereof, "References Cited." The data has been found to be readily available, mostly at the Colorado Geological Survey, or in repositories thereof, such as at the library of the University of Colorado. The data is neither very new nor obscure; therefore, any prudent geologist can readily gain access to exactly the same data which formed the basis of our opinion. This Consultant has examined available data from the public literature (see Enclosure 1, "References Cited") , studied the parts of the Harding Lawson Associates (HLA) report relating to the geology of the proposed landfill site, and also made a personal inspection of the location. We have subsequently formed an opinion which is as follows: It is most likely that fluids formed in the proposed landfill will percolate through breaches in the clay liner, created by continued subsidence. Once through the failed liner, the waste fluids will , without further resistance, follow the collapsed features into the abandoned coal mine workings and from there directly into the Fox Hills aquifer. 5757 Central Ave.Suite D Boulder.Co.80301 1303W43-2209 Telex 5101008402 Telecopier(303)443-3156 -2- Our opinion is based on a number of facts, each of which will be summarized below. Our first premise is that landfills, as proposed in the HLA report, will create fluids. The HLA report is quite explicit on this point, so we need not address that point any further. These fluids will accumulate at the base of the landfill in contact with the proposed clay liner. However, subsidence is still active in the local area of the proposed landfill , as determined not only by theory (see below), but also by field examination. Subsidence generally manifests itself by stoping from the old mine openings up through the overlying rock and soil until the surface is reached (Sowers, 1976) . Sometimes only cracks or fissures may reach the surface, other times troughs or "chimneys" may form depressions. Cracks may propagate to near the surface but not be detected from the surface (Appellate Court of Illinois, 1979) . In this particular area both troughs and "chimneys" have been experienced, the latter being sharply defined, circular pothole features. These are typically formed over large rooms, shafts, air shafts, and along ancient faults. Faults which show brecciation (intense fracturing) are particularly susceptible to chimney formation if located in a subsidence area (Amuedo and Ivey, 1975) . The order of magnitude of the offset created by the collapse of a trough or chimney, once reaching the surface, is measured in feet in the Erie area. Engineering geologists have determined a relationship between the depth to the mine opening, the thickness of the coal bed removed, and the width of the mine "room" as these factors influence the amount of subsidence (Brauner, 1973) . A recently formed chimney showing a 5-foot displacement was inspected immediately to the north of the proposed landfill area. The proposed clay liner is also of a thickness measured in feet. Therefore, it is our opinion that a collapse under the proposed landfill , once it reaches the liner, will create sufficient displacement to "pull the plug." The "plug" which is pulled down will also typically have a diameter of several feet, as historic experience has shown it in nearby locations of similar nature (Dames and Moore, 1986) . Alternatively, should a trough type of collapse propagate to the base of the landfill , then a ridge, ledge or crack may form over which the clay liner will be breached. In both cases the waste fluid will no longer be contained by the clay liner, but percolate into the underlying, loosely packed soil , and broken bedrock over the old mine workings. As described in the HLA report, groundwater movement takes place in the bedrock, rising and falling with the annual cycles of rain and snowfall , as well as being forced laterally along the piezometric gradient. This lateral motion is strongly accentuated at the level of the old mine workings where either actual open space or loosely packed and highly permeable rubble provides a conduit. Consequently, the waste fluid will mix with this groundwater and rapidly be brought into, first, the mine workings, and subsequently into the Fox Hills aquifer. The reason for this is that the coal beds were in direct contact with the Fox Hills aquifer (Chen and Associates, 1979) . 2111.161.9 -3- The proposed landfill area is geologically characterized by two local , structural features, trending in a northeasterly direction. These features are upthrown parts of a major fault system which is regionally known and detected. The features are called "horsts" (no relation with the landowner), and have by the coal mine geologists been observed to throw the coal beds and the underlying Fox Hills sandstone aquifer as much as 200 feet up higher toward the surface (Inactive Mine Program, 1982). The degree of throw varies across the area, but two distinctive horsts are running through the western part of Parcel One, and the entire part of Parcel Two, respectively. These horsts create a direct conduit between the old coal mine workings and the Fox Hills sandstone. Conversations with retired miners discuss this sandstone, which, when found at the fault, prevented further mining in that direction (Amuedo and Ivey, 1975) . Instead, the sandstone would occasionally cause flooding of the mines because of the water-bearing nature of the Fox Hills sandstone. Local differences in structure, elevation and pressure gradients caused variations in the inflow of water, just like these factors will influence both the direction as well as the degree to which the waste fluids will migrate into the Fox Hills aquifer. This Consultant, at this time, has not been authorized to conduct any determination as to the direction in which the waste fluid-contaminated water will move among the old coal mine workings and from these into water wells in the surrounding area. However, from just the ratio of permeabilities in unbreached bedrock (as used in the HLA report) , versus the collapsed troughs and chimneys and old mine workings, we estimate a similar ratio of reduction in the time it takes to reach the aquifer. Consequently, it is our opinion that contamination of the aquifer will take place only months, or, at most, a year or two after a breach of the clay liner by a subsidence feature. The accurate timing or specific location of potential subsidence is indeterminate. Otherwise, engineering design could possibly mitigate or prevent such an event. However, subsidence has been taking place during the last 50 years, both during mining as well as upon abandonment. It is taking place now and it will continue into the foreseeable future as discussed below. In some cases, pillars have been left among the abandoned coal mining rooms or panels, while in other cases they have been removed. Both scenarios exist under the proposed landfill sites. Further, in some mined locations, pillars, where left in place, are supported on soft shale (at the Columbine Mine in the southern part of the Laidlaw landfill area) , while others are supported on hard sandstone (at the Boulder Valley B1 Mine in the central part of the proposed area) (Amuedo and Ivey, 1975) . The pillars in the southern part would therefore tend to collapse first, while the northern part would be delayed. The mined-out areas around the Columbine Mine should therefore show substantial surface relief from already-occurred subsidence, while the area around the Boulder Valley Al Mine should show fewer effects and still expect the major part of the subsidence to occur. Personal observation of these two sites has 211,G1, -4- convinced this Consultant of this important difference. This difference in geology has perhaps not been considered by the Colorado Geological Survey when the Survey prepared its warning letter to Weld County (Soule, 1990) The propagation of subsidence may be accelerated by disturbance of the site (Boulder County Subsidence Investigation, 1986). For example, rumbling of dump trucks, not to mention removal of several tens of feet of rock as proposed for this landfill , will disturb the rock. There will also be a removal of from ten to twenty percent of the weight over the old mine workings, and subsequent filling and recompaction of the area when cell after cell of landfill operation is brought into function. This differential disturbance of the overlying weight can be expected to cause reactivation or start generation of new subsidence as the landfill is being operated. In short, the landfill operation itself can be expected to accelerate any new or remaining potential for subsidence. It is therefore the opinion of this Consultant that additional subsidence not only is unavoidable, but also that it will take place during the operation of the landfill . Consequently, contamination of the aquifer will take place immediately thereafter. The public literature and various mapping have previously warned against the hazards of this location. The HLA report presents maps of the local site (Figure 3 in Harding Lawson and Associates, 1989), but fails to note the warning on the original Subsidence Hazard Map (Amuedo and Ivey, 1975) which reads as follows: 'The only acceptable land use for these areas is • agricultural or open space.' If you require additional information about the threat to the water supply, both from the Fox Hills sandstone and from the alluvium in the city of Erie, please do not hesitate to call . Sincerely, GUSTAV ASSOCIATES �pr.�a A� "?•�, ,/ � 2fi37 �4'j '•� hn B. Gust v n, President Certified Pr essional Geologist #2637 Enclosures ,5` REFERENCES CITED Amuedo and Ivey, 1975, Coal mine subsidence and land use in the Boulder-Weld County coalfield; Boulder and Weld Counties, Colorado: Colorado Geological Survey, Environmental Geology No. 9. Brauner, G. , 1973, Subsidence due to underground mining: U.S. Bureau of Mines Information Circular 8571 and 8572 (in two parts). Chen and Associates, Inc. , 1979, Preliminary coal mine subsidence evaluation, three reservoir sites, Boulder and Weld Counties, Colorado: Chen and Associates Consulting Engineers, Job No. 17,707. Colorado Geological Survey, 1990, Proposed Horst landfill : Letter to Weld County Department of Planning Services. Colorado State Government, 1989, Solid wastes disposal sites and facilities: Colorado Revised Statues, C.R.5. 30-20-101-112. Colton , R. B. , and R. L. Lowrie, 1973, Map showing mined areas of the Boulder-Weld Coalfield, Colorado: U.S. Geological Survey Map MF-513. and L.W. Anderson, 1977, Preliminary geologic map of the Erie _puadrangle, Boulder, Weld and Adams Counties, Colorado: U.S. Geological Survey Map MF-882. , 1978, Geologic map of the Boulder-Fort Collins-Greeley area, Colorado: U.S. Geological Survey Map I-855-G. Dames and Moore, 1986, Boulder County subsidence investigation; State of Colorado, Dept. of Natural Resources, Mined Land Reclamation Division, v. 2, Final Report. Davis, T.L. , and R.J. Weimer, 1976, Late Cretaceous growth faulting, Denver basin, Colorado: in Professional Contributions of the Colorado School of Mines, Studies in Field Geology, v. 8, p. 280-300. Environmental Protection Agency, 1988, 40 CFR Parts 257 and 258 - Solid waste disposal facility criteria: Federal Register v. 53 , n . 168, p . 33314-33316, 33332-33335. Goldfarb, W., 1981, Three important court decisions: Water Resources Bulletin, v. 17, n. 6, p. 1097-1098. Harding, Lawson and Associates, 1989, Revised landfill design and operations plan, Horst Landfill , Erie, Colorado: HLA Job No. 17602,001.10. Ivey, J .B. , 1977, Ground subsidence as a geologic hazard in Colorado: Governor's Third Conference on Environmental Geology Proceedings, p. 33-41 . , 1978, Guidelines for engineering geologic investigations in areas of coal mine subsidence: A response to land-use planning needs: Association of Engineering Geologists Bulletin, v. 15, n. 2, p. 163-174. 01..6 .,9 I Walsh, James P. , and Associates, Inc. , 1989, Technical review of the landfill design and operations plan and other environmental concerns: Proposed Horst Landfill , Erie, Colorado. Rogers, W.P. , L.R. Ladwig, A.L. Hornbaker, S.D. Schwochow, S.S. Hart, D.C. Shelton, D.L. Scroggs, and J.M. Soule, 1974, Guidelines and criteria for identification of geologic hazard and mineral resource areas: Colorado Geological Survey, Special Publication n. 6. Sowers, G.F. , 1976, Mechanisms of subsidence due to underground openings, in subsidence over mines and caverns, moisture and frost actions, and classification: Transportation Research Record 612, p. 2-8. Turney, J.E. , 1985, Subsidence above inactive coal mines: Colorado Inactive Mine Reclamation Program Special Publication N. 26, Department of Natural Resources, Denver, Colorado. Appellate Court of Illinois, Fourth District, 1979, Village of Wilsonville vs. SCA Service Inc; 396 NE 2 d 552, 1979. Weld County Department of Planning Services, 1978, Geologic hazard area map of potential ground subsidence areas in Weld County, Colorado. �lf.i61.9 REVIEW OF THE PROPOSED HORST LANDFILL, WELD COUNTY, COLORADO for Concerned Citizens of Erie May 10, 1991 GUSTAVSON ASSOCIATES 5757 Central Ave. Su¢e U Boulder Cobmo.o 80301 °910619 REVIEW OF THE PROPOSED HORST LANDFILL WELD COUNTY COLORADO May 10, 1991 210613 Introduction Previous applications submitted for the proposed Horst Landfill site have been denied by the Colorado Department of Health (CDH); (CDH,1990). A copy of the denial letter from the CDH to Mr. Daniel Horst dated May 21, 1990 is attached to the accompanying letter from Shawn P. Mulligan as Exhibit A thereto. In the letter, several requests were made by the CDH for additional investigations and evaluations because of deficiencies in the application. Although the proposed Horst Landfill site has been reduced in size (in terms of acres) since the denial letter, it is still part of the original parcel of land (parts of W/2 of Section 21, 1N-68W) proposed in the previous application that was subsequently denied by the CDH on May 21, 1990. Therefore, it is our opinion that these requests made by the CDH for additional investigations and evaluations should have been addressed in the most recently revised application commonly referred to as the HLA report. A large number of published data have been used in the examination of this property. They are shown in Enclosure 1 hereof, "References Used." The data have been found to be readily available, mostly at the Colorado Geological Survey, or in repositories thereof, such as at the library of the University of Colorado. The data are neither very new nor obscure; therefore, any prudent geologist can readily gain access to the same data which formed the basis of our opinions. This Consultant has examined available data from the public literature (see Enclosure 1, 'References Used;') and studied the Harding Lawson Associates (HLA) report relating to the geology of the proposed landfill site. This Consultant has subsequently formed opinions that follow: 1. There is a very high probability that excavation of coal (undermining) has taken place beneath portions of the proposed site. 2. Moderate to severe subsidence hazards exist on portions of the proposed site. 3. It is most likely that fluids formed in the proposed landfill will percolate through breaches in the clay liner, created by continued subsidence. Once through the failed liner, the waste fluids will,without further resistance, follow the collapsed features into the abandoned coal mine workings and from there into the Fox Hills aquifer. 4. The proposed Horst Landfill, while sharing many deficiencies with the Zigan Landfill, has additional negative features that demonstrate its poorer site suitability. 5. Numerous inconsistencies, inaccuracies and misquotes were found in the HLA report that raises questions as to the accuracy of its report. S,l ..19 -3- Section 1: There is a very high probability that excavation of coal (undermining) has taken place beneath portions of the proposed site. In the HLA report, we found no maps or mention of any site specific investigations that show whether mining has taken place beneath the proposed landfill site. HLA indicates that the landfill boundaries are outside areas that have been undermined, but provides no maps or specific information regarding mine boundaries or extent of mining. In fact, based on the best available information (Amuedo and Ivey, 1975, Enclosure 3) it appears that portions of the site have indeed been undermined by the Columbine Mine. The map in Enclosure 3 (Amuedo and Ivey, 1975) shows the extent of mining from the abandoned mines with the approximate boundaries of the landfill site superimposed. In their report, Amuedo and Ivey state that the original mine maps, had for various reasons, questionable accuracy and that these maps do not always show the maximum extent of mining (Amuedo and Ivey 1975). Amuedo and Ivey cite cases of "poaching" by miners where coal was removed or poached as much as 200 feet beyond mine boundaries (Amuedo and Ivey 1975). Clearly, even being adjacent to a mine boundary as is the case with most of the proposed landfill site raises the question of whether additional portions of the site have also been undermined by the Boulder Valley #1 mine. Despite that the Colorado Department of Health (CDH) requested in the denial letter to Mr. Daniel Horst dated May 21, 1990 that the "existence, character and areal extent of mining beneath the site be investigated (CDH, 1990), the extent of mining has not been investigated. Also in the denial letter was a request to investigate the presence of void space beneath the site" (CDH, 1990). By not investigating the areal extent of mining beneath the site, the presence of void space has also not been investigated. Any mining beneath the proposed site will most likely create void space and result in a subsidence hazard of some degree. Again based on information in Amuedo and Ivey (1975), it is our opinion that undermining has taken place beneath portions o£ the proposed landfill site. Section 2: Moderate to severe subsidence hazards exist on portions of the proposed site. Subsidence is still active in the local area of the proposed landfill, as determined not only by theory, but also by field examination (Enclosure 4). Subsidence generally manifests itself by stoping from the old mine openings up through the overlying rock and soil until the surface is reached (Sowers, 1976). Sometimes only cracks or fissures may reach the surface, other times troughs or "chimneys" may form depressions. Cracks may propagate near the surface but not be detected from the surface (Appellate Court of Illinois, 1979). Enclosure 5 is a subsidence hazard map (Amuedo and Ivey 1975) showing the areas of subsidence hazards in relation to the boundaries of the proposed landfill site . Based on this CV1-"All eh +��_O1O, -4- map, moderate to severe subsidence hazards exist on the southern and western parts of the proposed site. The following is an excerpt from the Geologic Hazards Section (3.24) of the HLA report: "The hazard for subsidence induced by the undermined areas was evaluated on the basis of information and methods provided in Amuedo and Ivey (1975a) and mine maps obtained from the Colorado Geological Survey. Utilizing the mine depth data and methods for evaluating subsidence zones discussed in Amuedo and Ivey (1975a), subsidence safety zones surrounding the mines were established. For each mine adjacent to the site, as recommended in Amuedo and Ivey (1975a), a conservative angle of draw of 30 degrees was used to compute a subsidence hazard zone. The width (W) of the hazard zone is equal to the depth (D) of the mine multiplied by the tangent of draw (30°), or W = D x tan 30° Using the worst case scenario (D = 350 ft), the subsidence hazard zone for the _ mined areas is within 202 feet from the edge of the mined area. The boundaries of the proposed landfill area were established outside of this calculated potential hazard zone." It is not known if the above methodology for computing a subsidence hazard zone is in error or if HLA chose not to follow the recommendations in the Amuedo and Ivey report. In either case, it is our opinion that the 202 feet calculated above for a subsidence hazard zone is insufficient. An excerpt from the report in Amuedo and Ivey (1975) concerning the recommendations for computing the subsidence hazard zone is presented below in order to reveal the differences in assumptions. "Safety Factor - Factors such as angle of draw, attitude of bedding, and presence of zones of weakness due to faulting can extend the surface influence of a particular void well beyond the limits of the undermined area. Determination of the extent of subsidence at the surface is further complicated by the possibility of significant inaccuracies in the original mine maps. The effect of the inter-relationship of the above factors is not amenable to quantification. It is therefore prudent to incorporate a "safety factor" into the determination of the extent of surface area which might be affected by mining. This has been done by assuming a nominal angle of draw (35°). This angle was used in conjunction with the maximum mining depth (580 feet) recorded in the coal field to calculate the width (400 feet) of a safety zone which extends beyond the mine boundaries. This 400 foot wide safety zone is used throughout the entire coal field even though nearly all mines are less than 580 feet deep. The hazard classifications used for the zones of safety are the same as those used for the adjacent areas which are directly over the mine." � � � -5- The most obvious difference is that Amuedo and Ivey recommended using an angle of draw of 35° rather than an angle of 30° in the HLA report. If this is an error in the HLA report, then the boundaries for the proposed landfill site should be moved back at least another 43 feet for the affected areas of the site. Moreover, HLA did not incorporate other "safety factors" recommended in Amuedo and Ivey (1975) (e.g. using a maximum mining depth o£ 580 feet versus 350 feet), in their methodology for computing a subsidence hazard zone. In fact it is apparent that the boundaries of the proposed site overlap subsidence hazard zones established in the HLA report (Enclosure 6). Thus, even relying on the work of HLA, portions of the proposed landfill rest on land where there is a subsidence hazard. The 400 foot wide safety zone (which extends beyond mine boundaries) used by Amuedo and Ivey in constructing their subsidence hazard maps is approximately twice that of the 202 foot safety zone used by HLA in their report. Accordingly, a significantly larger portion of the proposed landfill may in fact rest on land where subsidence hazards may exist. Unless additional site specific investigation proves otherwise, it is our opinion that the subsidence hazard zones used in Amuedo and Ivey (1975) are the most reliable. On the western part and to the west of the proposed landfill site, a severe subsidence hazard exists due to the old coal mine workings of the Boulder Valley #1 mine. The subsidence hazard is severe because the pillars of have been left standing in this portion of the mine. Furthermore, the pillars are supported by a hard sandstone floor, hence a major part of the subsidence hazard still be expected to occur as a result of these conditions, see Enclosure 7 (Amuedo and Ivey, 1975). The denial letter from the Colorado Department of Health to Mr. Daniel Horst dated May 21, 1990 specifically requested that any subsidence hazards on the proposed site be investigated and address how these hazards could "affect the proposed design performance" (CDH, 1990). Because portions of the proposed landfill site are located in moderate to severe subsidence hazard zones, additional site specific investigations should have been conducted in order to comply with the requests by the CDH. In the HLA report, the presence of subsidence hazards on the proposed landfill site and how the hazards affect the proposed design performance have not in our opinion been addressed or to some extent even acknowledged. Again, it is our opinion that moderate to severe subsidence hazards exist on the proposed landfill site and these hazards have not been investigated in the HLA report. Section 3: It is most likely that fluids formed in the proposed landfill will percolate through breaches in the clay liner, created by continued subsidence. Once through the failed liner, the waste fluids will, without further resistance, follow the collapsed features into the abandoned coal mine S ?.f; -6- workings and from there into the Fox Hills aquifer. If boundaries of the site are located in subsidence hazard zones then it is our opinion that breaches in the clay liner will result from continued subsidence. Our opinion is based on a number of facts, each of which will be summarized below. Our premise is that the landfill, as admitted in the HLA report, will create fluids. These fluids will accumulate at the base of the landfill in contact with the proposed clay liner. The fluids will percolate through breaches in the clay liner created by continued subsidence and follow the collapsed features into the abandoned coal mine workings and from there into the Fox Hills aquifer. In this particular area both troughs and "chimneys have been experienced, the latter being sharply defined, circular pothole features. These are typically formed over large rooms, shafts, air shafts, and along ancient faults. Faults which show brecciation (intense fracturing) are particularly susceptible to chimney formation if located in a subsidence area (Amuedo and Ivey, 1975). The order of magnitude of the offset created by the collapse of a trough or chimney, once reaching the surface, is measured in feet in the Erie area. Engineering geologists have determined a relationship between the depth to the mine opening, the thickness of the coal bed removed, and the width of the mine "room" as these factors influence the amount of subsidence (Brauner, 1973). A recently formed chimney showing a 5-foot displacement was inspected immediately to the north of the proposed landfill area. The proposed clay liner is also of a thickness measured in feet. Therefore, it is our opinion that a collapse under the proposed landfill, once it reaches the liner, will create sufficient displacement to "pull the plug." The "plug" which is pulled down will also typically have a diameter of several feet, as historic experience has shown it in nearby locations of similar nature (Dames and Moore, 1986). Alternatively, should a trough type of collapse propagate to the base of the landfill, then a ridge, ledge or crack may form over which the clay liner will be breached. In both cases the waste fluid will no longer be contained by the clay liner, but percolate into the underlying loosely packed soil, and broken bedrock over the old mine workings. As described in the HLA report, groundwater movement takes place in the bedrock, rising and falling with the annual cycles of rain and snowfall, as well as being forced laterally along the piezometric gradient. This lateral motion is strongly accentuated at the level of the old mine workings where either actual open space or loosely packed and highly permeable rubble provides a conduit. Consequently, the waste fluid will mix with this groundwater and rapidly be brought into, first, the mine workings, and subsequently into the Fox Hills aquifer. The reason for this is that the coal beds were in direct contact with the Fox Hills aquifer (Chen and Associates, 1979). s • e, .� -7- The proposed landfill area is geologically characterized by two local, structural features, trending in a northeasterly direction (Enclosure 8). These features are upthrown parts of a major fault system which is regionally known and detected. The features are called "horsts", and have by the coal mine geologists been observed to throw the coal beds and the underlying Fox Hills sandstone aquifer as much as 200 feet up higher toward the surface (Inactive Mine Program, 1982). The degree of throw varies across the area, but two distinctive horsts are running through entire part of the proposed landfill site. These horsts create a direct conduit between the old coal mine workings and the Fox Hills sandstone. Conversations with retired miners discuss this sandstone, which, when found at the fault, prevented further mining in the direction (Amuedo and Ivey, 1975). Instead, the sandstone would occasionally cause flooding of the mines because of the water-bearing nature of the Fox Hills sandstone. Local differences in structure, elevation and pressure gradients caused variations in the inflow of the water, just like these factors will influence both the direction as well as the degree to which the waste fluids will migrate into the Fox Hills aquifer. This Consultant, at this time, has not been authorized to conduct any determination as to the direction in which the waste fluid-contaminated water will move among the old coal mine workings and from these into water wells in the surrounding area. However, from just the ratio of permeabilities in unbreached bedrock (as used in the HLA report), versus the collapsed troughs and chimneys and old mine workings, we estimate a similar ratio of reduction in the time it takes to reach the aquifer. Consequently, it is our opinion that contamination of the aquifer will take place only months, or, at most, a year or two after a breach of the clay liner by a subsidence feature. The accurate timing or specific location of potential subsidence is indeterminate. Otherwise, engineering design could possibly mitigate or prevent such an event. However, subsidence has been taking place during the last 50 years, both during mining as well as upon abandonment. It is taking place now and it will continue into the foreseeable future as discussed below. The propagation of subsidence may be accelerated by disturbance of the site (Boulder County Subsidence Investigation, 1986). For example, rumbling of dump trucks, not to mention removal of several tens of feet of rock as proposed for this landfill, will disturb the rock. There will also be removal of from ten to twenty percent of the weight over the old mine workings, and subsequent filling and recompaction of the area when cell after cell of landfill operation is brought into function. This differential disturbance of the overlying weight can be expected to cause reactivation or start generation of new subsidence as the landfill is being operated. In short, the landfill operation itself can be expected to accelerate any new or remaining potential for subsidence. It is therefore the opinion of this Consultant that additional subsidence not only is 21.C619 -8- unavoidable, but also that it will take place during the operation of the landfill. Consequently, contamination of the aquifer will take place immediately thereafter. The public literature and various mapping have previously warned against the hazards of this location. The HLA report presents maps of the local site (Figure 3.1 in Harding Lawson Associates, 1990), but fails to note the warning on the original Subsidence Hazard Map (Amuedo and Ivey, 1975) which reads as follows: "The only acceptable land use for these areas is agricultural or open space." Section 4• The proposed Horst Landfill,while sharing many deficiencies with the Zigan Landfill, has additional negative features that demonstrate its poorer site suitability. In previous work for the Concerned Citizens of Erie, this Consultant has evaluated the Zigan Landfill site. The nearby Zigan site is similar in that it is located in the same geologic province. However due to mining and localized structures the Horst site must be considered separately. Whereas the Zigan site was (and still is) considered by this Consultant to be a very poor location for a landfill due to geologic conditions and the potential for groundwater contamination; the proposed Horst site is considerably worse. Our opinion is based on the following: 1. The Horst Landfill site is situated in an area which overlies and is virtually surrounded by excavated coal mines (see enclosed maps; Amuedo and Ivey, 1975). The site therefore is prone to subsidence. The subsidence hazard for this area has been classified as moderate to high risk (Amuedo and Ivey, 1975). Although the Zigan site was situated in close proximity to moderate and high risk subsidence areas, no portion of the proposed site was within either an excavated region or an area of subsidence hazard. 2. The proposed Horst Landfill site is situated directly on a known faults. The faults trend southwest to northeast and extend through the proposed site (see enclosed maps Colton, 1978; Amuedo and Ivey, 1975; and Tweto, 1976 which is not enclosed). The age of the faults are unknown at this time. Recent movement along the faults has neither been proved nor disproved. The Zigan site, on the other hand, shows evidence of faults, but none have been mapped which transcend the site as in the Horst site. 3. Borehole samples taken within the proposed Horst Landfill site clearly indicate that the near surface bedrock is not only severely fractured, but also indicates shallow groundwater migration (Harding Lawson Associates, 1990). Oxidized (reddish-brown) mineral stains have been described in shallow fractured borehole samples within the Horst Landfill site which clearly indicate near- S lAs61.9 -9- surface groundwater movement (Harding Lawson Associates, 1990). This is further supported by Enclosure 9, a groundwater map (Hillier and Schneider, 1979). This evidence supports the premise that contamination of shallow groundwater in the area will occur if the landfill liner is breached or leakage occurs in the proposed Horst Landfill. Although shallow groundwater was found on the Zigan site, evidence of fracturing was not noted in borehole descriptions (White, 1990). The proposed Horst Landfill location is thoroughly documented by various sources as an area which is undermined, has moderate to severe subsidence potential, is fractured and faulted, and where shallow groundwater exists (less than 20 feet). Although, in the opinion of this Consultant, many of the same hazards are likely to exist at the Zigan site, irrefutable evidence of these hazards, such as those listed above for the Horst Landfill, was not available (for the Zigan site) at the time of application approval by the State of Colorado. Section 5: Numerous inconsistencies, inaccuracies and misquotes were found in the HLA report that raise questions as to the accuracy of its report. MISCELLANEOUS RED-FLAG ITEMS With all due respect to the firm of Harding Lawson Associates, this Consultant has noticed numerous inconsistencies, inaccuracies and misquotes in its written report regarding the proposed Horst Landfill. Some of the items may only constitute typographical errors or sloppiness in the best case. The statements could also indicate oversimplification or a genuine lack of understanding of the complex geologic and hydrologic area that has been recommended by the Colorado Department of Health for a thorough study. In the worst case, many statements represent misstatements of facts, oversimplification and oversights which, in the opinion of this Consultant, may border on negligence. Red-flag items that we have identified are discussed below. Page 8, lines 10 through 12, state the pillars were left in the Boulder Valley No. 1 mine but removed from the Columbine mine. This is in contrast to the maps published by Amuedo and Ivey (see enclosures) where the pillars have apparently been removed from most of both mines, but have been left in place in the main rooms. Page 8, line 18, states that Amuedo and Ivey (1975) used 30° as a conservative angle of draw. This is untrue, Amuedo and Ivey used 35°. Table 3.3, "Summary of Packer Permeability Test Results", is noted to contain packer failures in each well. The results of these tests are therefore viewed with skepticism since the packer system did not provide an effective seal in each test. 1911:1613 3 -10- Page 14, lines 16-18, state that water encountered in borings DH-38 and DH-42 is below the planned excavation depth of 20 feet; however, on page 13 the maximum depth to water is listed to be 6.21 and 12.22 feet, respectively for these borings. This is also in contrast to the well completion diagrams for the specified wells where the water depth is above 20 feet. Page 17, line 12, doubts any connection between perched groundwater and the Laramie-Fox Hills aquifer due to low permeability of claystone and shale, but fails to mention how fractures might otherwise enhance the permeability and hydraulic communication locally. Page 18, lines 8 and 9, state that "nonintensive activities" such as landfills represent the "best possible" land use. This has no basis in fact and is in contrast to the Amuedo and Ivey report of 1975 that suggests that such areas be used for agriculture, open space, open storage or unoccupied warehouses. Page 19, under 3.5.2, HLA admits that the landfill might impact the qualify of surface or groundwater in the area. Page 19, under 3.5.2, HLA states that low permeability of soil and bedrock exists and mentions that significant zones of high-permeability soil or rock were not identified. However, numerous of the borehole descriptions include the words"fractured" and"intensely fractured" where permeability tests were not performed. Page 20, line 26, "will not result in any unfavorable impacts" is in direct contrast to page 19 under 3.5.2 which discusses the landfill "leachate migration that might impact the quality of surface or groundwater." Page 21 under 4.2.1 "the plan consists of an average fill below grade of 20 feet... with maximum localized fills of up to 40 feet.." is in contrast to statements made on page 14 lines 16-18. Page 40, lines 10 through 20, HLA, in contrast to some previous statements admits the leachate could migrate beyond the landfill boundaries... within the "weathered fractured bedrock..." toward Coal Creek, the Boulder and Weld County ditches, and eastward to the Little Dry Creek. Page 40, lines 21 through 27, and page 41, lines 1 through 18, fail to mention or calculate the rates at which leachate will migrate from the landfill through what is most likely highly permeable, intensely fractured and weathered bedrock what was described in the borehole samples. It also fails to mention the rate at which leachate will migrate through excavated mines. Therefore the subsurface fluid movement calculations are misleading and probably grossly underestimated. HLA fails to mention any potential impacts due to earthquakes. Enclosure 10 is an earthquake occurrence map published in 1979. Being that the town of Erie and vicinity is o1-;619 -11- located where earthquakes of Modified Mercali intensity III to VII have been felt. This fact and its impact relative to the proposed EPA regulations of August 30, 1988 - 5. Section 258.14 Seismic Impact Zones has not been addressed in the application. 21'.1061.9 LIST OF ENCLOSURES 1. References used 2. Coal mine subsidence and land use in the Boulder-Weld coal field, Boulder and Weld Counties, Colorado, by Amuedo and Ivey 1975. 3. Extent of Mining Map 4. Subsidence Inventory Map 5. Subsidence Hazard Map 6. Subsidence Hazard Map (Modified as per HLA) 7. Mine Pillars Map 8. Geologic Map of the Boulder-Fort Collins- Greeley area, Colorado 9. Depth of Water Table Map 10. Earthquake from 1870 through 1979 and Potentially Active Faults in Colorado Map Sit i619 ENCLOSURE o 1.061.9 REFERENCES USED Amuedo and Ivey, 1975, Coal mine subsidence and land use in the Boulder-Weld County coal field; Boulder and Weld Counties, Colorado: Colorado Geological Survey, Environmental Geology No. 9. Appellate Court of Illinois, Fourth District, 1979, Village of Wilsonville vs. SCA Service, Inc.; 396 NE 2 d 552, 1979. Billings, M.P., 1972, Structural geology, third edition: Prentice-Hall, Inc, New Jersey, 606 p. Brauner, G., 1973, Subsidence due to underground mining: U.S. Bureau of Mines Information Circular 8571 and 8572 (in 2 parts). Colorado Department of Health, 1990, Application for certification for the Horst Landfill, letter to Daniel Horst. Chen and Associates, Inc., 1979, Preliminary coal mine subsidence evaluation, three reservoir sites, Boulder and Weld Counties, Colorado: Chen and Associates Consulting Engineers, Job No. 17,707. Colorado Geological Survey, 1990, Proposed Horst Landfill: Letter to Weld County Department of Planning Services. Colorado State Government, 1989, Solid wastes disposal sites and facilities: Colorado Revised Statues, C.R.S. 30-20-101-112. Colton, R.B., and R.L. Lowrie, 1973, Map showing mined areas of the Boulder-Weld coal field, Colorado: U.S. Geological Survey Map MF-513. and L.W. Anderson, 1977, Preliminary geologic map of the Erie Quadrangle, Boulder, Weld and Adams Counties, Colorado: U.S. Geological Survey Map MF-882: , 1978, Geologic map of the Boulder-Fort Collins-Greeley area, Colorado: U.S. Geological Survey Map I-855-G. Dames and Moore, 1986, Boulder County subsidence investigation; State of Colorado Department of Natural Resources, Mined Land Reclamation Division,v. 2, Final Report. Davis, T.L., and R.J. Weimer, 1976, Late Cretaceous growth faulting, Denver basin, Colorado: in Professional Contributions of the Colorado School of Mines, Studies in Field Geology, v. 8, p. 280-300. Davis, T.L., 1985, Seismic evidence of tectonic influence on development of Cretaceous listric normal faults, Boulder-Wattenberg-Greeley area, Denver Basin Colorado: in The Mountain Geologist, Rocky Mountain Association of Geologists, v. 22, n. 2, p. 47-54. Environmental Protection Agency, 1988, 40 CFR Parts 257 and 258 - Solid waste disposal facility criteria: Federal Register v. 53, n. 168, p. 33314-33316, 33332-33335. Goldfarb, W., 1981, Three important court decisions: Water Resources Bulletin, v. 17, n. 6, p. 1097-1098. Harding, Lawson and Associates, 1989, Revised landfill design and operations plan, Horst Landfill, Erie, Colorado: HLA Job No. 17602,001.10. , 1990, Landfill design and operations plan, Horst Landfill, Weld County, Colorado: HLA Job No. 17602,050.10. Hillier, D.E. and P.A. Schneider, Jr., 1979, Depth to the water table in the Boulder-Fort Collins-Greeley area, front range urban corridor, Colorado: U.S.G.S. Environmental Geologic and Hydrologic Studies, Map 1-855-1. Ivey, J.B., 1977, Ground subsidence as a geologic hazard in Colorado: Governor's Third Conference on Environmental Geology Proceedings, p. 33-41. Kirkham, R.M. and William P. Rogers, 1981, Earthquake potential in Colorado, a preliminary evaluation: Colorado Geological Survey, Department of Natural Resources Bulletin n. 43, 171 p. , and William P. Rogers, 1985, Colorado earthquake data and interpretations, 1867 to 1965: Colorado Geological Survey, Department of Natural Resources Bulletin n. 46, 106 p. Robson,S.G.,A Wacinski, S. Zawistowski,J.C. Romero, 1981, Geologic structure, hydrology, and water quality of the Laramie-Fox Hills aquifer in the Denver Basin, Colorado: U.S.G.S. Hydrologic Investigations, Map HA-650. Rogers, W.P., L.R. Ladwig, A.L. Hornbaker, S.D. Schwochow, S.S. Hart, D.C. Shelton, D.L. Scroggs, and J.M. Soule, 1974, Guidelines and criteria for identification of geologic hazard and mineral resource areas: Colorado Geological Survey, Special Publication n. 6. Sowers, G.F., 1976, Mechanisms of subsidence due to underground openings, in subsidence over mines and caverns, moisture and frost actions, and classification: Transportation Research Record 612, p. 2-8. ij, IS 99 Turney, J.E., 1985, Subsidence above inactive coal mines: Colorado Inactive Mine Reclamation Program Special Publication No. 26, Department of Natural Resources, Denver, Colorado. Tweto, O., 1976, Preliminary geologic map of Colorado: U.S. Geological Survey Miscellaneous Field Studies Map MF-788. Walsh, James P., and Associates, Inc., 1989, Technical review of the landfill design and operations plan and other environmental concerns: Proposed Horst Landfill, Erie, Colorado. Weld County Department of Planning Services, 1978, Geologic hazard area map of potential ground subsidence areas in Weld County, Colorado. White, K. R., 1990, Landfill design, operation, and closure plan for the proposed Environmental Recycling and Disposal Co. facility in southwestern Weld County, Colorado: Project No. 8912-04, 82 p. , 1990, Plates 1 through 8 for Landfill design, operation, and closure plan for the proposed Environmental Recycling and Disposal Co. facility in southwestern Weld County, Colorado: Project No. 8912-04. 81(561 ENCLOSURE 21ts619 ....._.. ._ The Amuedo and Ivey report is not included in this copy. Sit..s'61!9 NOTE: The following enclosed maps present the reader with data, specific to the proposed Horst Landfill. The maps are copies of portions of published, full scale maps or portions of other reports listed in the Bibliography of this report. The maps have not been altered, modified or presented in any way which might falsely project their contents or original state of being. The only differences between the enclosed maps and the original published maps are in some cases the scale and the color. We have further superimposed the boundaries of the proposed Horst Landfill on the enclosed maps for the benefit of the reader. ENCLOSURE 210619 11 �✓ r , . I Iu \ 1 A- � '5,I 1 AU �1 _417 ----/— 1, ........ 1. x15 - . )Action . _I '\ {•. CLAYTON I �? 1 t _Now WEST ( ) � . I� rig �� . 70� �. � ,J �� _ ti� '� ',OSED ORS � ' < c o �o:�_' D �ll,-_i 5/ ilipn / N\--111\s-) I c) U ,•�, _— �- r�' D / \ ! °• `+4"-COULD I °� / 1V ( �� AIItEY# ! 1! -6 I __ G N � ,I3rI,\ ' - / F HIi i N.455 1NG-TOIt- / ! -f< .. I ,i_ 5 _- — .-__-• -_ - - —- • _ alb CO MBINE i% ' L- ( C z , r -_ D II ;le N,uE� = � - Vii:, II o4 d -a o , � � 77-��I � •G� ' -� kt "a z& 8-----X-----� 27 -- u,. �,� i !- 'w AI , 11 c, ,, \ , N. _ l U el 1 ,^t r �/ I S., - I , . / \ I : . \ CC. TI .I iD f:X: " I _ _ 6 6 , 4 p i l4 I- GMa F I , I S - / �e 33 laYl 34 / ii a/ U 1JYJ ( � 'iy7eu '�' I I es 4 I I I.,;de ROAD Wrien CO " \ \J ° Dr, z I I _ oo oraLoamu 'WIVE I \ F ca.oc SUBSIDENCE INVENTORY MAP 45. Reportsappeared indicate that during mining, lance In fields widet cracks \ ande soed along road here due Go subsidence In fields to north BOULDER WELD COAL FIELD \_ BOULDER D WELD CDUHt E5 iv's DO and south. I ENCLOSURE '310619 T E ._�� I�" 1✓ � - , ,fit , I NKNoWN u f ti ► „{ 'a�Bn MINE, /.; /) �" "� � / +r �I - : s D (!' ' 417 , , ; , ti w► • �► RT +WEST''‘ al' / 1 ,t i. �. CLAYTONI , S, � d / �� i ,•r� - -'''�O$ED: OR ' ' � � �,,,, •11u�11, n R ` _ '-,rv�..w. ,rro -� r f/ ... /--/ I .Bw. • � II r 7IN L kw } III ! � I 1 r. ilwr • Abp. �MIMt "Br �.. 4' - R I U Q 1 F Jo/uLo —= �' �II F / A EY# I ww SEER�elrrm N S� �+ � -°� ' i`: l � s - ; �' W Tr r / - ,' / �� e f �. � // N� yarwGlor, C_ , '� 5 03 • ` ' .. :: ' rte 1 rs --.'•••••--;9'.../..---7�' i ) . C O II N E _- �I".! : i JN ' - E 7--,- z_ 511.._ . ---. — ///y C.... ,' " I l � ��_ \lI /:::: /� 1 I i t'.. D ,- 4. . '1 III ,..., k. .`:.. _ 16 / _ � ' _ III. 7 �i - I .1:::),c• w r `� 4 ' C • \ O l"� . I• SC 14 LBBBB \ ' 33 3411 / o .... ....2 .1 � � , i .Sc MINE PILLARS u t" 6 •i- 'o i.e. _8 LS C` mco..00 ecoLo.en 90,,n V C (/ f1 _ �7 MINE PILLARS MAP f X Y• „ PILLARS LEFT I BOULDER—WELD CaAL FIELD IF R.NB Raw / BOULDER AND WELD coorts•coLORRDo I. �fiW Wfl,b CO / (� PILldR5 REMOVED • ` � ....'. .u...u. o.....a ..'.•.o-.a.on ; { rlA i z .°� •lt•o 11k E .t.-,!,, V• ENCLOSURES ✓11L61 1-.!..", `III.Nell .014 / .4 MINE/ , f. ii Y i I 6 U p � � s d Il I' ' r :'' w ,P:,'1 WEST FI 't ( \ . •\ \'S•-‘1 .. .-.-\., •, CLAYTON I / Y ' t l�l l r. / I, „`' . pSELl ORS; lP � I t� Iri a .� 1 O • 4 +,. _ ' 198 a../ �� ., ;i�'j ♦.. 1 'i F� �.. !E • _ (} i u; ° •t / _ . f3 EIS / , T E Y I �' I L / • $�� Yee OULD/ 5 ' � - y, �// / y �'�• 2/ << �,' r :: i ; f� 1 —�s NyiNcTT-ON w El r e,' :.. / .� :r — 1 t 1 5 C Is i r. d -_— — -- - _ 5 OJ F , 1 '• I MBINE • L , _ . �� ✓ S r -• v < ti' c . ' </ • k �1 (� l ___c_:.1---- 27 • ' - - d i \`. - a 1 1 �' ( C �. I - lJ ril �� o i �, oodede tt 't _ 1 "eV' 34 �--- 1 itai . 12 � . � J \ I (7.,_:, �. ./ +.. _� a_ / � . _ - _ _ X-71 211c°g. _= V -- f ;_ \ I �, VI " 1 t' i I ,\ A I Lone dr v — � 1 i) 3 3 ' i )) _ G •-•.,‘: ( 5,.9: ( . � � - —B I �. /- EXTENT OF MINING - , l i ' p /t AMceoo ANC lye). t / This Slvdy eaeo+soo aeo.00 uc rw.e. (\ _ Al11e p+Mr ( [orlon and Lowrie .'J I E%TENT OF MINING MAP = . \-----(Rte{ woo co 6 X ti i----- \ ,i 1 >� O �. BOULDER—WELD COAL FIELD ..„. ......4,.,.. Lo+'rlr. 966 1 I T� 90U4oed AND YIELD COUNTIES E ,COLOR ADC ,,,.... ,4.... SJiX) e.l A- -IS'."J p'4. l r. . v ' I I I. , �� - I 1 Jr•.)O - t ENCLOSURE 9113619 I� ' r ' 9 1 %� i•I t �13� � . • i V _ • k-. ,-, _, , ,_,_, .y 4,14,4„,44,,.. r ' a NKNOWN y. y• / i • •d s/ �; i MINE/ ' 11 / 1 ' i , , If , / fr/ t • t/ ifti u - 7fA, WEST: - k _ , LAYT0 " 'i , j � I • - / .� i .I iri r� I r of ,',, I , r . 't . �' '•Q$ED, • RS ��. +► , �� _ ,,� .�' kdi� ' y ,.......) •/�I ��/� /�A , f y .LL .... . .• 4 y / ' � EY /r 1 / ( I -' K . � � • � ' § I /..- _- f r o �►. -- -- - ' • emu : I /% �•I y -� \5 03 ) y .. 11' t / yliif\i • 7:. . ,,, , , __ � � _ Y -, l- r !\ ��--- tti ' (- >j-1.C k� k � •� % j CK ., / c, \ ' , 1:;„,./r.7 _---; :y - / ua J A //L ////////��raaa-�� i� ✓I��' `� f 1 1'. I r ' - l vJl tf13 ' sysc•.ESURVEY I, —' �� a3 \/ r 1 ! ' \ SUBSIDENCE HAZARD MAP ! daDz -- \ - BOULDER—WELD COAL FIELD • _ — . • •a,. _ I I BOULDER AND WE_0 COUNTES•COLORA00 l I/ , "' f • ••.QR. .. U I ! \ / B 2,71..).---)1:"....),),\2/2) ~f \T TIIE PURPOSE OF THE SUBSIDENCE HAZARD MAP IS,TO LABEL THOSE AREAS WHERE THE LAND SURFACE WILL BE AFFECTED BY SUB- __ I . _ y : 1 -2SIOENCEPELA '0UNDERMININ6. E `" 1 THECLASSIFICATION SYSTEMON THISIMAP IS BASED UPON THE DEGREE OF IIAZARD WHICH MAY BE EXPECTED AS A RESULT OF THE /:� VAPIOU5 CHARACTERI5TIC5 OF THE UNDERLYING OR ADJ�ICENT HINE WOPKINGS AND THE PRESENCE OF FAULTING. THIS INTEPPRETATION M \1 IS AN ATTEMPT TO SHOW TIE ZONES NI{ERE'A MAJORITY! OF THE AREA CONFORMS TO THE GIVEN LATE DOPY. FURTHER DETAILED ANALYSIS JAY MAY LEAD TO RECLASSIFICATION OF SOME AREAS. I /4 f SFVF RF - ZONES LIBELED SEVERE!pqE AREAS IN WHICH THE EFFECTS OF RAPID SUBSIDENCE SUCH AS FAILURE OF BUILDING FOUND- I' [[ ATIONS, ROADWAYS, GAS MAINS, AND SIMILAR FREQUENTLY USED, OR POTENTIALLY DANGEROUS FEATURES MAY ENDANGER LIVES OF PERSONS R 6CI W. %� IN THE IMMEDIATE VICINITY. SUCH AREAS HAVE BEEN: UNDERMINED AND ARE CHARACTERIZED BY T) THE PRESENCE OF PILLARS AND PHYS- ICAL EVIDENCE OF VOID SPACE, OR Z) BY ABSENCE OF, EVIDENCE OF SURFACE SUBSIDENCE. THC COLLAPSE OF DECOMPOSED PILLARS COULD INDUCE ALMOST INSTANTANEOUS 'SUBSIDENCE OR DISPLACEMENT WITH EQUALLY OR ALMOST EQUALLY RAPID DESTRUCTION OF STRUC- TURES AT THE SURFACE. THE ONLY!ACCEPTABLE LAND USE FOR THESE AREAS IS AGRICULTURAL OR OPEN SPACE. 1 n0DFRATF - AREAS SUBJECT ITO MODERATE SUBSIDENCE� ENCE ARE DEFINED BY'POTENTIAL SURFACE DISRUPTION OF SUFFICIENT MAGNITUDE ��\ TO DAMAGE STRUCTURES TO SUCH AN EXTENT AS TO RENDER THEM UNSAFE OR UNUSABLE. THE RATE OF SUCH DISRUPTION HOWEVER IS SLOW \-`��\` ENOUGH TO ALLOW TIME FOR RECOGNITION OF THE PROBLEM AND SAFE, ORDERLY ABANDONMENT OF SURFACE STRUCTURES. THESE AREAS ARE LHAPACTERI ZED BY EVIDENCE OF PREVIOUS SUBSIDENCE OVER UNDERMINED AREAS WHERE PILLARS WERE LEFT. THIS CONDITION PRODUCES THE POTENTIAL FOR FURTHER SHALL SCALE COLLAPSE ANO DIFFERENTIAL SETTLEMENT. ,APPROPRIATE LANG USES MIGHT BE AGRICULTURE, OPEN STORAGE SUCH AS STOCKPILES,'LUMBER YARDS, OR UNOCCUPIED WAREHOUSES, AND OPEN SPACE. I LOX - ZONES OF LOW HAZARDJARE AREAS IN WHICH THE RATE AND MAGNITUDE OF ANY SURFACE DISPLACEMENT WOULD BE SMALL ENOUGH TO WARRANT REPAIR OF,DAMAGE TO EXISTING STRUCTURES AND APPLICATION OF ADEQUATE ENGINEERING DESIGN TO FUTURE STRUC- - Y/;;;�� TURES SO THEY CAN WITHSTAND SWILL AMOUNTS OF FOUNDATION DISPLACEMENT, THESE ARE AREAS BELOW WHICH ALL OR ESSENTIALLY ALL �)<7.��' PILLARS HAVE BEEN REMOVED ALLOWING THE POSSIBILITY OF RELATIVELY UNIFORM AND COMPLETE SUBSIDENCE TO HAVE OCCURRED. PROB- LEMS IN SUCH AREAS SHOULD BE REDUCED TO POST-SUBSIDENCE COMPACTION AND RELATED SURFACE SETTLING, AND TO SMALL-SCALE EFFECTS OF SUB-SURFACE SHIFTING RESULTING FROM ANY SMALL RESIDUAL OR SECONDARY VOIDS, THE ONLY RESTRICTIONS PLACED ON LAND USE WOULD BE THE REQUIREMENT FOR ADEQUATE STRUCTURAL DESIGN OF ANY STRUCTURES PLANNED FOR THESE AREAS, AMUEDO AND IVEY LEGEND i COLORADO GEOLOGICAL SURVEY O AIRS„AFT SUBSIDENCE HAZARD MAP e MINE SHAFT (Hoisting Shall) ' f HOCK SLOPE Unit BOULDER—WELD COAL FIELD i...-----D FAULT BOULDER AND WELD COUNTIES ICOLORADO --------- MINE BOUNDARIES SCALE' 124,000 CONTOUR INTERVAL; 10' .-----7------ HAZARD AREA BOUNDARIES GEOLOGY J.O.IVEY . J.L.HYNES GRAFTING H.A.H. SCHLENDER DATE: DECEMBER I , 1974 MAP N0. 7361-6 • 211-C:'L,3 ENCLOSURE • r �.; I 1 ./� v ..� ` / "le I '..,,•,_sue 00 / �. La.....,_, E r 1 I f .. � ( • u 5 • E 1 _ • 1 4 I' I` � CLAYTON } L�. . , ii it \v k C.-1 / 4 � .1 �� -i- L - ' 1'. f � 1$ ',, SERI QRS i 1 _ °4PRII;�II�e. Li /j - " - / {' Y l ,( ,) ire _ 1 7 \: t� \ 1 EIS / s / / I � . ,f < , r�11N� :0ULDFF��22 I / f 2 h / 42 i rlf I 7 % i _ �iW, �`. ��gr :yAii.. raid / / Q om,• .t� (.i �° �1 Nl}$tjINGTON; �� q e� • �.• .. 1 C---- --�'V ��wb l I� . �l =y -j -I �V N I , �f�,�6 • i/'� � ' N � 3 � ^ MBINE ' " D - �' ' rl J C .75 \ � 2 ` �� ,. "S� .. , :t \, • �// ((•. 14.�.w ,.. / --_ — - �. ,i i_ _ r y< is — 'I J l I , A _ ,, • I,N -- F 1 \1 \ Sq;7_____,_5( ____{ Ura♦� • ( ' ____3.:_ji- S VI )-lier ___1:, / - - .r• 33 11: \ 5191 I 1 • El' - _ SUBSIDENCE HAZARD MAI" .//�'J` II N i Showing subsidence hazard"zone"of 202 Q; l ,f�1 1l calculated by Harding Lawson Associates, 1.990 -ei Ache Raft ( 'I'y' 1 4� wpm CO J n •subsidence hazard no calculated l/r by Harding Lawson Associates, 1990 S 4 �v v zone ' nmdi(icJ from Cztcnl of Mining Map by Ann,cdo and Ivey, 1974 + v P ' x �0 ENCLOSURE Yo'' tr,; I,� / •• ••/ '._ uri do ,"-- . •., ..,k4. Y •• 1 ` f- f Y J ��-...• . �. . `) • •• N.1i� • •• + I • • ..', ' �� U ; D f - 5oi3. � � • J • I1J ' , �' •• Fi I sU (/ 52111 • i1. / . • •• • • , ' I • , t . ._h K ,� .• \ ••, 1 J . . • •o , • • O. . • t . / • •; l r .�• • , �� D / $t4te "pal M m ,' !\ .•• o, • Q ♦ f �. -fit-; 1 ♦ V fr i In • I • • • ♦ \ •- ..1 t •I O • .• r • • • t • ' ' ,• 7 Cem 'U � • • • •. • •, , n • II •' •. •` • .'• N Itional ; • P ' OROS£D HOR1ST LAN U FILL National / / . . I • l) ) • • / N) ci, • .' 4, , . , ) , ,•" a , • / �, ,.- I\...c 1 6• .. 4 (7.I •:COCCI? ' : t • • „•� �• , • • �_ • i • • ..l ' "ED 48 i 8. tip_ , • vID 1 V ^ �� ,.� l• - . _ . . ..rte . . ✓✓ - ( r f r - ♦ • �, r% A A A . • , i" . . .• F. • • 1 ♦• • r' CONTACT • •' . . . .. '+•• / \ J �l • — FAULT OR I(NEAR FEATURE INFERRED TO BE A FAULT— D f • �• • w •.O / Dotted u oere concealed U,upthrown side; D,downthrown ' , • cJ side; cro shatched area is breccialed rock ! .. _ .� � _� ARP TERRACE S ...._ _- i1/4, �— DCFLATIOP BASIN (HOLOCENE TO PLEISTOCENE)— '' } _ 1' 5 • Closed repressions eroded by wind action and,perhaps, by•• , • ,� f wtfle an.bI'en. Floored locally by thin deposits of clay,sill, . •• 1 •• K I ' •, and san I; elsewhere by bedrock or older surficial deposits J ,•� I - ♦ _�::_ CREST OF )UNE • ••' •• C_____, + . \ ,• "-'-'- LEEWARD MARGIN OF MIGRATORY DUNE GROUP • •' V • • • • • • ,•• �—r——'— BURIED CH 1NNELS UNDER BEEBE AND EATON DRAWS ` , O >V GEOLOGIC MAP OF THE BOULDER—FORT COLLINS—GREELEY AREA, COLORADO BY :;.:Seini8W120118ttegiter4B810441 Roget1978 Colton 11J611.9 ENCLOSURE .9 0 6.1 \' 1 �\ C "',\ ! 1 ,i, 1 • 1 id • 1..• , — . • ~iYiM I �,j , (' Gcrrl •- NTatiOnal .1 : �Q � ,n�r _ ` ! b'� .,_. 7Pt�5 )1) H�0R T LA FILL' iNl1 ■ fT �Y r r' n u . u, , �. l *�\ x � N, v , Le. YM 1� 1 ti.,.V'/'1/ 7-• ...„,. ....k.- , J ,x ffir,. ^!x "n• /V,,/ .n •._rn "•r. • af. N� •S' , -,..,.. 187 1 (� (f J `I .•r .•,. ,i l wage )sp 1,,tiI'"^n DEPTH TO THE WATER TABLE (1976-77) ' R. 6 8 W . IN THE BOULDER-IFORT COLLINS-GREELEY AREA, FRONT RANGE URBAN CORRIDOR, COLORADO By • Donald E. 'Hiller and Paul A.Schneider,Jr. 1979 EXPLANATION INTRODUCTION The depth to the water table is a hydrologic factor that can be used by DEPTH TO WATER TABLE IN UNCONSOLIDATED ALLUVIAL and local officials to assist them in making decisions regarding Ian DEPOSITS! IN FEET BELOW LAND SURFACE conversion in the rapidly urbanizing Boulder—Fort Collins—Greeley V „a '"- Less than 5 (index map) reiri4.revrro,,. 5to10 10 to 20 p`'m7 ti' Greater than 20 4 S_11/A l`.--S AREA OF THIS REPORT AREAS WHERE UNCONSOLIDATED ALLUVIAL DEPOSITS �___ Fort Collins o I 1. Greeley ARE NOT PERENNIALLY SATURATED—Depth to seasonal I I water table generally ranges from 5lO 20 feet.Where areas are arm titer not irrigated,the deposits usually are drained by mid summer. I DeNvrtR Where areas are irrigated, seasonal water table may remain through the growing season with drainage of deposits occur- ring during the autumn AREAS WHERE LOCALIZED WATER-TABLE AQUIFERS Grand Junction =''aSr-. I (\Colorado Springs r_ OCCUR IN COLLUVIAL, LANDSLIDE, AND WIND- BLOWN DEPOSITS, AND IN CONSOLIDATED SEDIMEN- TARY ROCKS WHERE ROCKS NEAR LAND SURFACE Pueblo ARE FRACTURED AND WEATHERED—Aquifer materials I COLORADO may not be perennially saturated;depth to water table gener- /� ally ranges from 5 to 20 feet; depth to seasonal water table I \ I 1 generally less than 10 feel _ r. w AREA WHERE LOCALIZED WATER-TABLE AQUIFERS `-- 'Sef M OCCUR IN FRACTURED CRYSTALLINE ROCKS—Frac- MAP SHOWING AREA OF FRONT RANGE URBAN CORRID tures may not be perennially saturated; depth to water table may be more than 100 feet t Depth to water table generally less than 20 feet In localized areas of unconsolidated alluvial deposits (not shown on map)occurring in stream valleys traversing fractured crystalline rocks. CONTACT BETWEEN UNCONSOLIDATED ALLUVIAL DE- POSITS AND OTHER DEPOSITS AND ROCKS.—Dashed This report presents the results of a 2-year Investigation to determine the r where approximately located to the water table,water-table fluctuations and trends,and to relate the n of the investigation to urban planning.The report is one of a series of ger ' ' EASTERN OUTCROP LIMIT OF FRACTURED CRYSTAL.- and hydrologic reports prepared by the U.S. Geological Survi LINE ROCKS demonstrate the usefulness of earth-science information in urban plar *14.2 WELL WHERE DEPTH TO WATER TABLE WAS MEASURED In the Boulder—Fort Collins—Greeley area, the principal water IN 1976 OR 1977—Number is depth to water table, in feet aquifers consist of thick unconsolidated alluvial deposits that are peren below land surface. saturated.These deposits occur in present and ancestral stream valleys z CS, Well completed in consolidated sedimentary rocks terraces both along present stream valleys and on slopes of the foothills E F, Well completed In fractured-crystalline rocks the Front Range (diagrammatic section). - W. Well completed in windblown deposits All other wells completed In unconsolidated alluvial deposits 03'6 WELL COMPLETED IN UNCONSOLIDATED ALLUVIAL DEPOSITS WHERE DEPTH TO THE WATER TABLE WAS MEASURED FOR AT LEAST 4 YEARS DURING 1971-75.—Number is average depth to the water table for the 21.0619 period, in feet below land surface (Data from Major, Kerbs, (r+ WINDBLOWN DEPOSITS cawvAL DR LANDSLIDE DEPO$ns LOUlIPNI wailer id*I and Penley, 1975) Localised wele,laeleNONE. "WIN" "IN Omni...NH*0.d*NNW&BENIN chained O WELL COMPLETED IN UNCONSOLIDATED ALLUVIAL / NrrlNW PEI RE nth Vest @. LL / PRINCIPAL WATER TAM animas DEPOSITS WHERE DEPTH TO THE WATER TABLE WAS Y w ., CIPAL WAT R alluvialTAME anim MEASURED BETWEEN 1955 AND 1975 r perenniallyNVunted . U ---- --TERRACES— PRESENT TERRACES STREAM .l VALLEY FRACTURED '.+ y ''''7",''': 1,j-1 — � l(Need el l roolsob \ blflkeaw torlse CONSOLIDATED SEDIMENTARY WArER�._-�', W Mrdlerr In \ I,IBna lUdnyrvWr2 ML 1 nN$nl lnFp 111• 1 rer ano \ toe nd AR wrlllwrod Al IMAM nrronIs • DEPTH TO THE WATER TABLE Ranges tudepth to the water table sham on theme('were delineated only lm Menuned depths to the water table during 1976-77in the unconsolidated them nterilets all vap deposit deposils ranged l o to 45.6 len Genemly the depth lathe water Locally twerreable aquifersalso ream In ihr ripper weathered And laid In tim Pond dens ol present streams was less item IO feel and,in many tinctured mne of consolidated sedimentary rocks th i form the foothills ravi nl Inrnlllles II woo lose than 5 feet.The depth to the water table in nnrestral the Dont Range mel Ind coon mot in Ihe a.fen pad of11 +:in rolirwid stream valleys.such As Beebe Draw,and In tht_ s ranged h 0.5 to and landslide deposits occur s Oral , e.O slope. 1 il consolidated 45.6 I I Water I I. _wells completed 1 1 I windbl n deposits, sedimentary rocks:and In windblown deposits that cover much of Oa eastern consolhlaied sedimentary rocks, and fractured crystalline rocks were pa M tie emu. In the crystalline rocks that lorm the Front flange hi the mewined only in Wilder Grimly.In Ilse county.the depth M the water Inbk western pan of the area,matn occurs locally In Imctnres to a depth of alma In the windblown deposits ranger)Imam.T 10 12 led: in the consolidated 300 feel below land surface.Idagrnmmalk Fa nod.Because of live localised sedbne,JAry rinks,II rnmlM Imm l do 291eeI;and In Ow lmcmred cryvaAlna °eminence of these water intik mluilers and because some of the aquifer HAAS,n ranged Imm 9 In 193 let material nd!whirrs I I e.l for pad nf lbe yersc,th .nrwifers were nevi Th h M1s t water.level me. enh madk nl nppmxlmatrly - studiedhr delllflorin!'this Mw.INpllo Whew I levels a tired _ eel Drop present - In wok re pleted In them localized tweeters,only the locations of use writs die same Hine each year loellmkate the ell J.of seasonal flrchalkm of and the measured depths lo wider are shiner mat the depth-to-water naps water table.The hydregmphe Indicate awl.velh a few exrnMlmsc no egreAc- Adesianaervilen,which«Cur in the consolidated sedimentary rocks in lire ant upward or downward trend In thewater table Wsdeveloped since the late °.moat pad of the area,were nM shelled dndnl Ibls Investigation. 19501 Water levels were measured mace in 120 wells during 1976 m 1977 to The dela In the table Aker Indicate that,with a few exceptions,Ile.eater determine the dentin°IM water table tickliliwat int°mak*,shard'Imola< obi"Ollie area was al them'the same WWII,In theta,.19501 n In 197f)7. In by'mob,lrwls were measured k Inchnkmr in n tams by Srhnelder turd Of the 31 walls Ned In IM Ishii,,wales levels In.3 of Ilse wells have declined IAIIkr1197R).A coimpahnn betweenwafer levels measured during 1976_7) more limn 5 feel;the maximum decline was 9.R feel.No water levels have and water levels measuredbythe U.S.Geological Survey shoe thelate l 9!A's rinrn mere titan 3.1 feel. hiArca*iihrra grourcr water whininge h inaiiw InBkalvd Him no sgnlAcmJ Alesindema clamward trend of water kook,whkh may indicate lh,water upward or drwnwent bend in the water,able has developed in mot of the • k hmlml prnnprd nr mined Imm are nee(Ms)ill A Yale Mai l grealeir Ihnn the m during the lad 20 yens.Thnefore,water levels repotted lw Mar, role of nohow lntim amriferlsl,haplarenl on the hydrngrtpirs Mille wells In arc sa_9 T.4 N. R.td W. I I . .. 1! T. N. B.fR W Data re nM Kobe and PvnW1)enel SchneiderMuds by ldrillers rllswere olio sufficient.however,I verify thatground-under mining I.n naming.Mlning nil mph llershry li9611 argl water kvda reixrcled by k IIA nwex oath ground wrerdn may by ocrurMm In name pads of the Area 1 . .conlInnal supplement nor 1976-77 detain the cmnMhatinn of the depth-in-waterm+p .• kurn.Ienn usnlrr IwylcMta era coed availal.k.The darn kiln,laMe hx the WAS l br rcpnnnd dale weze obtained from the flb of CdnrnaInDerv+amnm nl In see 20.T.2 N.,R.69 W.(decline of R I feel)aml In sa.27,T.J N., NMerml Iesonrers.lAWJnn 01 Woler Newurnrs.Olike of the 5h+ti,Engineer. It G)W.(dedlma of 9.8 tail may be indkative of mound.wryer mining. Physiography and geologY(Colton, 19711 also were used In the if Wound-Wider mining B uMmg,continued pumping 1 Idprg wells a1 mmMhllon For example,the presence of swamps was used m delineate Ile same or Demme(' .1 N result in the IoAewang sentience Mcent. : n.O arras where depth ter Om water leek Is less than 5 fed.Alone the Smith I.Water levels decline,well yields decrease,and pump intakes have lo be Plante Ricer and Ids principal Idbul rte, the character of the mapped y,n„rrvl In Ilw palls. _ depihmre howirlaries often needs the boundary between Ilw Anent 2,Wells have to be derpenrd,insmmelocalities In nw ham of the agieler, d South tu IM1l Arch Hain and Ih terraces.Also,bo IIw flood M•+tns of Ihr and Intakes lowered to m near the bottom of the well as Ixweble.ll this Soo J MMte RI And Ms chmch I hell I de.Aar gr and o der between p p theyon Md AM M,klsdect used inI1Ndc le . Ilerdl W m, h not been tunepmwlnrdy which enure I higherne to are .ch in contortion rdlh 0 able k T. Notions re A. I eel Wryer levels of d -w t. features aquifers may mar b to delineate areas I Ih¢depth to Ilw wales table h des Pumping decline gwell.could ere is d'p lellksl connection oe l sig iAcatlmm nlly loveand III levels In II S eel. Appreciationroels extended In s many x,k own ti Boulder—rod aiInstalling Additional inds.and pea in I 1 t Firing d only fr A �G ally Ikon's Ion ten nNg a ass to a I u.II f oft elate their teal Su ey mo G.IIAA FIN ewellsl,and lum Doug Coun of the.U.S a I. 1 e sequence. of . t.let e above.Th. .al of. potentialfor Gok.rkol Survey pmexlnl all JAIa Inc wells In Boulder Cognty. Ion,grmmd-wan timining nos Iw.lms thee red In he evaluated 1 Mnnnttg Inc when decelnl,menl. RELEVANCE TO URBAN PLANNING LIMITATIONS OF THE INVESTIGATION The depth lo Ile water tehle h n relevant factor In planning for urban The users of Iles mend need mhe Aware that he water.habie data represent deveinpme I as Wheeled d Ivy the IdmNnq examplm., cnmpilation of water levels measured throughout 1916 And 1977.W earne A.1leleb to the water table kless than 51.l either seasonally or a,nnnlly f seasonal or annualon-Idiom In groundwater recI r discharge,the I.The effectivenessMIndividual thimmikw 11.1 e_ytems meld dale I t necessarily represent either dlm shallowest nr ihegreaten depth t he unlined And unheeded wastescook enter the.ground-wryer system.Some the t. table that ceivoki occur ore has owned Water.lewl immurement, of the lent kl reactions A NI Iwith individual' <to-dlspenal sµlens III loin I. 1 dad ImI the frig Ihl.l 11 Itreh perhaps rnr In the umaturaled mane I kw or adjacent io IM system.Because.the Ihrorybout Ihr wit al a specific site Intended fm r specific se tdetermine, reactions do nee nCrur ill wmlal,the greater the depth In dm%MIMI table.the live potential Mini of water levels on lire re of the Ole.The.vale re the map greeter the pnanMAty dud thw reariinns will complete Ihv,conversion of ten Ibis repnd precludes ha use lm specific One selection:anger vale maps need weer le an effluent that Is not a health hnmrd. to he used fed this immerse.Also areas of shallower depths to the water table • 2.Road and highway stability could be Mrected.Puldk acces<in Wilk ,Ian Ihnn shown on dh map occur focally,especially around Ih edges of myld he limited where marshy groom(exhls. lakes,ponds,and remnnna,Along canals where leakage°rain;and in the 3.SogsOink emblemscould mkt The li/pel of vee,ailon that could he stream°alleys where the depth lo the water table is shown In the move Irons grown in Ibrm nrem world h dependent on,M degree of IIm milrtny,huh to 10 feet. even whittled arty Wintry Problems,nary types of vegetation could rid grow h these areas. 4.Unstable sMl structure,whkh often AmH Ilve pal of land.amid exist. 5.Comlructbn of si ndural or building foundations could he hampered by the Aar of ground water Inln the commlMkn excavation. 6. Basements could be sublect to collapse tom wryer pressme and Handing SELECTED REFERENCES The sllunlbm described In Items 4.5.And 6 also could occur In areas Colion R.Il- 1978,GRAMM Map M the limddee—Fors CoAlirrGredey where the depth to the water table h not mtimthan 10 led either seasonally or n.Cnlamlo,U.5 Geological Survey Miscellaneous Investigations Msn An u.ako I-6 55-G il. IMMh in the wain table related to depth of asddlattnre. Jenkins E. D.1961,Rrrmtk and legs of elated wells and tee Wes,Anil I. Uqukr wages or leaclates nom saki waste could he Intrndured ciwinkal awl radiomen-lc analyses of ground water in the Boulder Area. dieecIty Inm the mnund.wated system by w+ire moldy through landfills and Coked..Colorado Water Cnmema,Imr lbard R+sbl late Report 5..nrp reaped lopes of LdAlks.remdtlnp In dQpadatkar or preholinn of are 9rnpnnl Maim.T.J,Kerbs,Lynda.and hydro R.D., VIM Sedmrrd noire level Sumer.l bw npsddAlly nldegmdalhn or pollution would he dependent on the records for Colorado, 1971-75: Colorado Waler Goawallaa Ildavl type aced amnunt of waste,terleryloMmrin1 of the waste,And lhesensomi re Iesk-11ma Release 37.3.5s p. annual depth of the WTIOI table in Ida Arra of the landfill m related type of Sdmekler,P.A.,Jr_1962.Records and imp of related well<anti Ire alp - Axaly, and dmnkal artatyses of ground water hr the Sineb Ilmir liner hen In 2 Ground water could ewer leaky military mums. rentilbet In a mitten,Admen and smelrrrernt Weld Connie). Colorado. Colonel° inillo-an,be mace wits wean,n,wave in he pr•^ardlwemar benbnenr Water Conservation Board flask-D.+a Rrrod 9,M p. imilines I venom°of wain roaring n leaky sinewy sewer would be Schneker,P.A...b.and Ilenh y.1. A..1951,Recant;and Irq<of wind dependent on thee&rbeRmrtalolsewer and the seasonal or annlr.+Idepth to wells and net hire,and nhemknl analyses nl guy ind water in the ken the wain Iabk. Carl,°In Pouch River basin,Colmadn Colorado Wain Conservation 3.The placement of electric And telephone Wililylies below mound and Rinanl flask-Dad lienrnq Ul P. the rype of houallon and conduits inquired for below.-gerund Installation Seinnit,,p.A...I..end d Mir,R II,I°ln I Ma.MrN nai.i h.r la.....rnmk• wood be.In pry,dependent on the depth to the water able ametee le Om thukier—Fart Collis—Greeley arch.Fme Waver Winn Corddor,Colorado: U.5.Genlopkal Survey(Aen1A1e Hemel IRLrJ, 5 p. e�,titu_1� ENCLOSURE 10 s19 ( , \ N G , --- /;.--�+ -Ti' . % `-- .:. \s -- j' ". ^., mow.".. --_ m i__. /.a f-� " 1k crx \" w d _ 1 'f`Y \ 'y \h. ` 1 a. ,r «. r \it./ R,^ 8 li n. "'. awn "., .. ,� \ ♦ o c 1 , a • � _ r Ml ' �'� \ I 1 -1 ( \Y 10 \ t n, � y — 1 . /" \ a p is —�. '�� I �� / \ l -l' i o +1 J I "fkf x l t 'c::,I li �'�� . . s 2 G.. _ rr It I `r 1 1 \1 i IC% ' ^\ AL' i'. .. 'i, -r`r,g' ` I1 Y_" ..4— -9-:�s.F—c- '�-.'—h�'=-- \ 1J�... I • � ( ♦ p �: 4@ ' x 5 5 \, 4 �1 Jr I ''' '-'..--1- TA. Je� ' � p � �� t I / a � a p �� ve ..., c �— + I a�>f� t+�� I , v J - cue C fee LAktwoio I it r1/4 11 j I :.. �7 n ,I r � l R 1 A .1b JAI, i 1 ,:‘ ,...,,,. (, i H� !O A+ E '- V1/2 1I i I d I 1 • v� —::- --i-er--, -7V , 1 I , � � i 11 � .... X11 g , �. -, / 1 1 .. 4 �_I "�, \A I - i . , �r a , I / ,: \ ' I\l' / fr�1 _ h �� f I�: o • .� q �I 1 E 14 1 I � �� l� , .I :1 �.... _ , ' h. v �:: r � iii. /. ..I �' 1 . k� ., ..... 1 ;� "• ,x ,v i� } 1 �.. , e A�' -:(1 �—� —� -- : 1 / I-. I 1 % v Ir �� I � ' is r � a I T^ ,� ..- I �\ rI - 'tom I. I „,_ ) 1, ... i, .. I ` `1' r ,- ;o �j Earthquakes from 1870 through 1979 - �' —'t �: �'-�� f 't-= I �.'�4 “` / � and Potentially Active Faults in Colorado .-I �.`:M:.: i j T E � p,��n� • .fir d \. #7_ , ry„., 'c 5PfAftldY by 1 l -N k ( I �� AQ Robert N &rkha . M cjat,4 � Ncl‘C I,^� w �n L IV V- �.�� l._� mod: " A�� , I s"... I- Someone else j I will need them too! I /, ti Bulletin‘ 43 iw • i / ., i i 5 Plafk 3 PLEASE RETURN ALL MAPS J 1981 COLORADO ---„%\ TO POCKET 1.7 Earthquakes from 1870 through 1979 K A — — 7.:±12,7) ! �n - and Potentially Active Faults in Colorado 1- I n v , 1 I by 1 Robert M. Kirkham and William P. Rogers -- - --: _ , 1 . , _c `T ,; —P-`--- EXPLANATION 1 •1 o Epicentral location of an earthquake of magnitude .I 2.5 to 3.9; only selected earthquakes of this j--1 magnitude range are plotted near the Rocky _ 1 Mountain Arsenal O I Epicentral location of an earthquake of magnitude 4.0 to 4.9 1 w a. - .,....., (� M f A . •3 ----- rc Epicentral location of an earthquake of magnitude - ' 5.0 to 5.9 _ \ `> - I Location and intensity of a felt earthquake of "'I Modified Mercalli Intensity III to V; only • ki selected earthquakes of intensity III are 7 plotted �,, I,, y r(` Location and intensity of a felt earthquake of ! � Modified Mercalli Intensity VI 7 ) r r. ,H A ( .. / ((/ fl0 Location and intensity of a felt earthquake of Ait r Jr , Modified Mercalli Intensity VII A 6 ) A �fY " ._.r... ,, -~ ' "' Q nuclear explosions detonated as part of the �_ Plowshare Program; magnitude 5.0 to 5.5 ,i/.4-.1- - ,.1 / vs' \ Potentially active fault (from Plate 1) i l Jl \\ ' � a SHAWN P. MULLIGAN BOULDER.R. COLORADO 80304-4267 13031 x)38-87.;0 May 10, 1991 Hand delivered Austin N. Buckingham Geologist Solid Waste and Incident ►management Section Hazardous Materials and Waste Management Division Colorado Department of Health 4210 East 1 1 th Avenue Denver, Colorado 80220-3716 Re: Application for a Certificate of Designation for the Horst Landfill (Revised 1990) ("Horst Application" or "Application") Site Location: One mile southeast of Erie--W 1/2, Sec. 21 , TIN, R68W; Weld County, Colorado Dear Ms. Buckingham: On behalf of the Safe Ecological Environment Committee ("SEE"), I submit for your consideration in the the above-captioned matter, the enclosed materials: this letter; the accompanying technical report, its support materials and attachments thereto ("Gustayson Report");and two letters from Don and Marilyn Brand and Tom Konetski. It is my understanding that individual members of SEE will also be submitting comments on this matter under separate cover. SEE respectfully requests that you include the enclosed materials, as well as any additional comments received from its individual members, in the Administrative Record in this matter. SEE is an organization, whose members' economic, aesthetic, and other interests will be deleteriously affected by the Hazardous Materials and tilaste Division's ("Division" ) approval of the Horst Application. The purpose of this letter and accompanying materials is to set forth SEE's position that the Horst Rpplication does not meet the minimum standards set forth under applicable Colorado law, specifically, those standards found in the Solid Waste Disposal Sites and Facilities Act, C.R.S. 30-20-101 et seq. and regulations promulgated thereunder, the "Regulations Pertaining to the Solid Waste Disposal Sites and Facilities," 6 CCR 1007-2 ("Regulations"). Support for SEE's position will' be set forth below in this letter and the accompanying materials. Because the Rpplication does not meet applicable standards, the Division may not, under Colorado law, approve the Rpplication. Therefore, SEE respectfully urges that the Division deny the Rpplication. I. HORST'S RPPLICRTION FOILS TO MEET THE MINIMUM STRNDRRDS UNDER RPPLICODLE COLORADO LOW The Regulations at 1 .3.2 set forth, in pertinent part, that "(s]ites for new sanitary landfills shall comply with the standards of sections 4.1 and 4.2...". Sections 4.1 and 4.2 of the Regulations set forth the minimum site and engineering design standards applicable to all new facilities for the disposal of solid wastes. Additionally, the Regulations at 2.1 set forth the minimum standards to which all solid waste facilities must conform. Because the Horst Rpplication proposes a new facility that fails to conform to these applicable regulatory standards, the Diuision should deny the Rpplication. R. The Horst Application Fails to Meet Minimum Standards under the Regulations Pertaining to Site and Engineering Design Standards Section 4.1 and 4.2 of the Regulations set forth that all new facilities must conform to the site and engineering design standards found in those particular sections. Important standards to which the Horst Rpplication do not conform are found in these sections at 4.1 .5 and 4.2.3.1 I Although the Rpplication, at Rppendisi R, provides a guide where the Rpplication discusses Information perhaps relevant to certain regulatory sections, SEE submits the estposltion found In the sections does not confirm substantive compliance with the referenced sections. Indeed, based on faulty information and questionable assumptions contained in the Rpplication and the Information In the Gustayson Report, Section 4.1 .5 sets forth that: Facilities for solid waste disposal shall isolate wastes from the public and environment by emphasizing favorable geologic conditions over engineered improvements of marginal geologic conditions. Section 4.2.3. sets forth that: Geologic hazards, or conditions including but not limited to slope stability, faulting, folding, rockfall, subsidence or erosion potential, shall not prevent the disposal site and/or facility from complying with the act and these department regulations. fis recognized by the Division itself, in its May 21 , 1990, denial letter on an earlier version of this Application, the Applicant proposes "to establish a public sanitary landfill over an area that is known to be undermined " Letter from the Diuision to Daniel Horst at 1 (May 21 , 19901. ("Division Denial Letter") ( R copy of this letter is attached hereto as Exhibit Rl. AS demonstrated by the Gustayson Report, and supported by the Rmuedo and Ivey Study, a study conducted for the Colorado Geologic Survey (a copy of this study is attached to the Gustayson Report), Horst has failed to demonstrate adequately that his application proposes a landfill in an area that is free from undermining' , a geologic hazard. Division Denial Letter at 1 . In fact, the Gustayson Report directly contradicts the Horst application, suggesting that a considerable portion of the currently proposed landfill does rest on land that is potentially undermined . Gustayson Report at Section 1 . In the face of two conflicting technical reports, SEE respectfully requests that the Division place its reliance on the more credible information, which SEE believes is found in the Gustayson Report. Rt a minimum, the Division should require rigorous field investigations to ascertain the true nature of the land underlying the SEE does not believe the Application can demonstrate substantive compliance with applicable standards. See generally, the Gustayson Report. In fact, Horst s failure to demonstrate adequately the undermining of the area underlying the landfill and the associated subsidence data is a violation of the Regulations requiring submission of pertinent geologic data. See Regulation 4.4.4. SEE submits this deficiency alone is sufficient for denial of the application, and would urge the Division to act accordingly. proposed landfill. See Division Denial Letter at 3. Upon formal investigation of the true extent of undermining in the area. SEE is confident that the Horst Application would reveal a site truly unsuitable for a solid waste landfill under applicable Colorado standards. Accordingly, because of Horst's failure to demonstrate that the landfill does not rest on undermined areas, because of the probability that portions of the landfill, do, in fact rest upon undermined area, and because this undermining is a geologic hazard, approval of this Rpplication would violate Sections 4.1 .5 and 4.2.3. SEE, therefore, respectfully urges the Division to deny Horst's Rpplication. The Horst Rpplication also fails to meet the standard found in the Regulations at 4.2.1 . This standard requires that: Groundwater shall be protected from water pollution by leachate from the facility for solid waste disposal. fls supported by conclusions in the Gustayson Report at Section 3, SEE submits that the placing of a landfill on an area where significant migration of leachate may occur, constitutes a violation of this provision. The Horst Rpplication should therefore be denied. B. The Borst application, by Failing to Prouide Key Technical Information, Cannot Demonstrate Compliance with Minimum Standards The Horst Rpplication fails to characterize adequately the complicated hydrology in the area. In absence of the Rpplicant providing sufficient pertinent information regarding the hydrology in the area, it is difficult to determine whether the Rpplicant could comply or does comply with other potentially applicable standards found at: 4.1 .3 (dealing with significant aquifer recharge areas); 4.1 .4 (dealing with siting of landfills based on distance groundwater would flow during life of facility); and 2.1 .2 (incorporating any applicable health and water quality standards). SEE submits that, in absence of providing such information, Horst cannot demonstrate compliance with the applicable standards, and the Application should thus be denied. nall II. HORST'S RPPLICRTION FRILS TO PROVIDE INFORMATION NECESSRRY FOR THE DIVISION TO PERFORM ITS LEGAL MRNDRTE UNDER THE KT RND REGULATIONS. In the Division's Denial Letter, the Diuision called upon the Applicant to provide the Division with information that the Division deemed necessary for it to perform its role under the (let and applicable regulations. See generally, Division's Denial Letter, at 2 and 3. See especially, Division's Denial Letter at 3 ("Due to the deficiencies of the application presented above the Division can not adequately evaluate the site suitability, the design and design performance."I Without the information it requested, the Division could not make an informed, legally supportable decision to approve the Rpplication. The situation has not changed--even the most cursory review of the most recent application by Horst indicates that the Rpplicant wholly failed to provide a great deal of the information requested by the Department. EHamples of technical information requested by the Division, but not provided by the Applicant, are found in the Gustayson Report. SEE respectfully submits that to approve the Rpplication without the information previously sought by the Division and required by applicable law would be an arbitrary and capricious act, subject to review and reversal. Accordingly, SEE would request the Division to deny Horst's Application. III. CONCLUSION SEE recognizes the limited review capacity of the Division under applicable law and regulations. SEE, however, believes the Rpplication submitted by Horst does not meet a number of legally applicable standards. The Rpplication is deuoid of necessary, technical information requested by the Division and required by law and as such is deficient as a matter of law. Rccordingly, SEE respectfully submits that the Division deny the Application. Furthermore, SEE urges the Division to allow SEE to comment on the legal and technical sufficiency of any additional submittals by the Applicant, if any, required by the Division prior to any additional consideration of this Rpplication (or any revised version of this Rpplication). Thank you for your consideration of SEE's submittals. If you have any questions on this letter or any accompanying materials, please contact me at the above address or phone number. Sincerely yours, Shawn P. Mulligan, Esq. cc: State Representative Faye Fleming State Senator Jim Roberts Weld County Commissioners Erie Town Board Safe Ecological Environment Committee Land and Water Fund Enc. 6 241(- 71-1 ESHIBIT 8 siN"B�*y"r{e E, �,,,J Jul./.��r.9 STATE OF COLORADO COLORADO DEPARTMENT Of HEALTH 4210 East 11th Avenue Tektax: J Denver.Colorado 80220.3716 (387)322.9076(Main Building/Denver) `,' t,• Phone (303) 320.8333 (303)720.1529(Ptarmigan Place/Denver) (303)246.7198(Grand Junction Regional Office) Roy Romer Governor May 21, 1990 Thomas M.Vernon,M.D. Executive Director • Daniel Horst Certified Mail #P 140 732 450 2240 Weld County Road 5 Erie, Colorado 80516 Re: Application for a Certificate of Designation for the Horst Landfill Site Location: N 1/2 Sec 20 and W 1/2, Sec 21, TIN, R68W; Weld County Dear Mr. Horst The Hazardous Materials and Waste Management Division (the Division) has completed its review of the application for a Certificate of Designation for the Horst Landfill proposed at the location cited above. This review was made under the authority of the 'Solid Waste Disposal Sites and Facilities Act,' Title 30, Article 20, Part 1 of the Colorado Revised Statutes 1986 as amended (the statute) and was intended to determine compliance with the requirements of the xRegnhutioas Pertaining to the Solid Waste Disposal Sites and Facilities,' adopted for the implementation of the statute and contained in the Colorado Code of Regulations, 6 CCR 1007-2(the regulations). The application proposes to establish a public sanitary bedfill over an area that is known to have been undermined by both the Boulder Valley No. 1 and the Columbine Coal Mines. Undermined areas are generally subject to subsidence which may be difficult to predict House Bill 1041 (CRS 1973, • 29-20-101, et seq.) identifies mine subsidence as a geologic hazard. To date the applicant has not adequately investigated the possibility and the nature of subsidence locally. The current regulations that directly affect this issue of subsidence are: I 4.15 Facilities for solid waste disposal shall isolate wastes from se the public and environment by emphasiting favorable geologic • conditions over engineered improvements of marginal geologic • conditions. May 21, 1990 Dan Horst Page 2 423 Geologic hazards, or conditions including but not limited to slope stability,fanking, folding, roekfall, subsidence or erosion potential, shall not prevent the disposal site and/or facility from complying with the act and these Department In addition to the current state regulations, the new EPA Municipal Solid Waste Disposal Criteria (known as Subtitle D) are brought to your attention. The applicant should address the ability of the site to meet the federal site restrictions Briefly stated, Section 2%15 of the proposed rule defines subsidence-prone areas (subject to the lowering or collapse of the land surface either locally or over broad regional areas) as an unstable area. Further; municipal solid waste landfill units located in unstable areas must demonstrate to the State the structural stability of the unit. This demonstration must show that engineering measures have been incorporated into the design of the unit to mitigate the potential adverse impacts on the structural components of the unit that may result from destabilizing events. Based on state law and regulations and the guidelines from EPA, it is believed that in order to proceed with the review, the applicant must demonstrate to the Division's satisfaction that destabilizing events will not impact the designed performance of the facility. The applicant should plan to investigate the following: L The. enstence, character and areal extent of mining beneath the 2. The presence of void space beneath the site; 3. The evidence that subsidence has or has not occurred (in the form of drill hole data, surface evidence and aerial photography); 4. A determination of how the subsidence hazard can affect the proposed design performance; S. A determination of how subsidence can be accommodated by the design; and 6. The areas which should be avoided. ei a !,f_s':.9 May 21, 1990 Dan Horst page 3 The region of the proposed landfill is known to be heavily faulted. Though not active during the Holocene, these faults may serve as conduits for ground water and leachate movement. The Division feels that the complicated local geology and hydrology have not been adequately characterized. The applicant has not assessed the potential for and the impact these faults may have on the movement of leachate, perched water and ground water, both horizontally and vertically. Station 4.1.4 of the regulations state: Facilities for solid waste disposal shall be sited no closer to domestic wells or springs shown to tap the uppermost aquifer downgradient of the site, than that distance ground water beneath the site would flow during the facilities' operating life, unless adequate ground water protection is provided. The applicant must evaluate the potential for major faults and fracturing (resulting from subsidence) to enhance fluid movement. Other major issues the applicant must consider are: 1. The rumored upgrading of the Tri-County Airport to accept turbojets and it's proximity to the proposed facility; and 2. The use of the drag strip on Section 20 as a private aircraft runway and it's proximity to the proposed site. Due to the deficiencies of the application presented above the Division can not adequately evaluate the site suitability, the design and design performance. Therefore, the Division is denying this application. This decision does not preclude the submission of a revised, detailed and comprehensive document at some future date. Though existing State regulations and the proposed Federal municipal solid waste regulations do not specifically prohibit siting a landfill over an undermined area, the Division feels that it would be very difficult to demonstrate the integrity of all landfill components in the event of differential subsidence. If the applicant chooses to pursue landfilling within the boundaries of an undermined area, a rigorous data gathering effort resulting in a high degree confidence is required. The resultant application will be reviewed by both the Colorado Geological Survey and this Division. May 21, 1990 Dan Horst page 4 If you have further questions regarding this letter or regulations, please contact this office. Sincerely, 7/4 Austin N. Burkinghsrn ameki L darl�eyy ` Geologist Section Chief / Solid Waste and Solid Waste and / Incident Management Secti Incident Management Section / Hazardous Materials and Hazardous Materials and Waste Management Di • on Waste Management Division ABN/PLH/jw:6601K cc E. Ross, Weld County Commissioners W. Potter, Weld County Health Department R. Allison, Weld County Planning Department S. Hahn, Town of Erie D. Thornburn, Attorney for Town of Erie P. Rasasco, HLA J. Hines, Colorado Geological Survey J. Soule, Colorado Geological Survey ACCOMPANYING MATERIALS 21.C61.9 8897 Baseline Rd. Lafayette, CO 80026 May 10, 1991 Austin Buckinham Hazardous Materials & Waste Management Division 4210 East 11th Avenue Denver, Colorado 80220-3716 Re: Application for a Certificate of Designation for the Horst Landfill Site Location: W1, Sec. 21, TIN, R68W; Weld County Dear Ms. Buckingham: The purpose of this letter is to state our objections and to raise questions concerning the proposed Horst application for a 145 acre landfill near Erie. We are attaching the previous letter dated February 20, 1991 from the SEE Committee concerning the Zigan application since many of the comments are the same. Also, the previous Gustayson & Associates report on the Zigan application has validity and bearing on the Horst application. We still feel that the arguments presented on faulting are real concerns to the integrity of the landfill system. These sites are in adjoining sections of land with the Horst site being directly to the north of the Zigan site. In addition to the remarks expressed in the referenced letter, we have other concerns particular to this application on several points; namely, the adequacy and accuracy of information and testing presented, the undeniable subsidence dangers, the expertise of me. Horst, and the acceptance of tires and fly ash. The proximity of residents and potential development make the nuisance and contamination elements all the more pressing issues. We would again like to stress the fact that this application approval would lead to 620 acres of landfill in a four section square with expansions likely proposed. This is becoming Denver's Wasteland. People are trying to live and work there. Many simply depend on the Health Department to protect their health and the future environment of Colorado. We urge careful consideration. The undermining and subsidence remain as evident dangers, as stated in the enclosed Gustayson report. Not only are some areas of the proposed landfill still in mapped subsidence areas, but the precautions on reliability in the attached Amuedo and Ivey study encourage further testing of specific areas before development. Listed below are page numbers and paragraphs which are supportive of our arguments. page iv, paragraph 1 page I-2, paragraph 1 & 2 page II-1, paragraph 2 page III-7, paragraph 2 & 3 page III-8, paragraph 1 page IV-3, paragraph 2 page IV-4 page V-2 page V-7, paragraph 1 page VIII-2, last paragraph page VIII-3, paragraph 1 & 2 page VIII-10, Safety Factor Sections on Faulting page III-5, paragraph 3 page III-6, paragraph 2 page VII-1 Extent of Report Investigation page iv page VI, paragraph 1 & 3 .C 6'19 These quotes will add credence to our position that further testing should be required at both sites and, particularly at the Horst site. Other Issues The applicant operated a landfill, currently Laidlaw North, which has been leaking VOC's to the adjoining property for the past several years. The first landfill cells were questioned by Mr. Leonard Slosky, an environmental consultant, as to their ever having been inspected. The landfill company chose to provide additional surety rather than investigate their integrity. The question arises as to the possible connection of the contamination and the uninspected cells. The predicted rate of leachate is mentioned. Does this concur with the actual rate of leachate flow from Laidlaw North? It would seem that the rate is much faster than that predicted. The Zigan application did have a few minor items that were somewhat better than the Horst application. The higher fencing of 12 feet is more desirable for control of debris inthese exposed and windy areas. Also, the Zigan application research into the site specific Columbine map and subsequent limited field work showed at least a modest effort. The real work of drilling to determine coal working was avoided by both applicants. Specific concerns would be their proposed acceptance of tires and fly ash. Tires can cause contaminating fires and can provide breeding grounds for rodents or mosquitoes. Below are a few quotes from the final draft of the Special Wastes Committee of the Governor's Task Force on Solid Waste presented August 15, 1990. "It is clear that tires, whether buried or piled, pose a large volume problem and may pose toxicity problems as well." "In addition, buried tires have a tendency to rise or 'float' to the surface, breaking landfill covers." "Ash may create an airborne danger during transport, or may leach hazardous substances into the groundwater if improperly landfilled." "Fly ash may contain concentrations of volatile metals such as cadmium, lead, arsenic, mercury, and zinc. In addition, dioxins and polychlorinated biphenyls (PCBs) may also be concentrated, but tests have not shown significant leaching of organic chemicals from ash." "In 1985, the EPA stated that ash that failed the EP (Extraction Procedure Toxicity) test must be treated as hazardous waste. This requirement has not been enforced, but it is important to note that fly ash samples generally fail the EP." "However, it is important to note that some ash, under some conditions, may be capable of leaching hazardous chemicals into groundwater." The complex geology with heavy faulting and fracturing ,combined with the dangerous situation of subsidence, contribute to a very unacceptable level of risk to the public health. We would therefore strongly urge denial of the Horst application. Re//��ctfulj Submi ted, £'/fir l�C� • % X7-1— t�j Cc° n and Marilyn d 1/ members of Concerned Citizens of Erie and SEE (Safe Ecological Environment) Other members wishing to sign: Pat Rice Virginia Blacker February ;20, 1991 Hazardous Materials & Waste Management Division Colorado Department of Health 4210 East 11th Avenue Denver, Colorado 80220-3716 Dear Ms. Buckingham: The purpose of this letter is to express our objection to the proposed Zigan landfill and recycling center. The reasons for this opposition are numerous. Future land use potential, residents' nuisance concerns, residents' safety and health concerns, and certain geologic conditions which increase risks to the environment and the residents. The past history of the area raises questions of the consequences of improper or inadequate planning and oversight. The two current landfills have made the residents familiar with the negatives associated with these operations. Any landfill has inherent problems - rodents, bacterial infections, air contamination, methane gas buildup, hazardous materials from households and small quantity generators and likely groundwater contamination. "Higher levels of contamination and thus, higher risks are associated with larger facilities that have a greater mass of waste. " "All other factors held constant, risk decreases with increasing distance from the facility." These are quotes from the proposed EPA Solid Waste Disposal Facility Criteria, page 3393. Therefore, we urge the Colorado Health Department, in rendering a decision on the Zigan proposal, to consider the significant effect on the human and natural environment which will result from the addition of yet another landfill in a limited geographic area. Within a ' mile, there are presently two operating landfills. A proposal for another landfill is pending CDH approval within the immediate future. We strongly urge CDH to review the Zigan proposal not as an isolated landfill application, but rather as one factor in an equation that will result in significant environmental impact. When viewed with other existing and reasonably foreseeable actions, the environmental consequences of four landfills, covering 620 acres, in immediate proximity one to the other, is profound. The existing Laidlaw Landfill, which is located across the street from the proposed Zigan facility has been documented as leaching toxic waste. EPA investigation of this site is underway. The proposed siting, like the existing landfill, is located directly over the Larimie/Fox Hills aquifer which services several drinking wells in the vicinity. The existing and proposed landfills all are situated within a triangle made up of residential dwellings. The risks of subsidence or geological instability which may jeopardize this precious water resource in Colorado necessitates a heightened level of agency scrutiny in consideration of such a location. Associated with this high density of landfills and the additional recycling center, is, and will be, a large volume of heavy truck traffic. Problems associated with this have been numerous already - danger from traffic, increased dust, and trash escaping trucks. Quiet country living with joggers, horseback riders and schoolchildren waiting for the bus, can be endangered on the narrow dirt roads or fast, smooth paved roads. One woman testified in Erie about a truck overturning in her yard and burning. Dump trucks drag racing in nearby eastern Boulder County were also mentioned in testimony. Laidlaw's July 12, 1989 traffic count was 428 in 18 hours. Zigan estimates 200-250. This represents a tremendous impact on this small area. page 2 This being the highest elevation within two miles causes additional problems. It seems logical that any contamination will not remain easily contained. The high visibility makes it difficult to screen from view, noise and lights. The current sites already carry bothersome noise to the old part of Erie, about 11 miles away. Winds are logically more intense - which means more blowing trash and a more unattractive blight. Prevailing strongest winds carry the litter generally to the east, where the residences are closest to this site. Zigan estimates that it is only 800 feet to the nearest residence! This will tend to carry noise, odors, as well as the blowing trash and contaminated air. The other predominant wind direction is from the southeast - which leads to the older part of Erie. The omission of wind data in this application should be corrected. We dispute the applicant's statement on page 10 USR "the geologic setting of the property makes it an excellent candidate for environmentally sound landfill construction". Gustayson Associates' report dated February 12, 1991 contests this statement with discussions of high probabilities of faulting and seismic impact. The geology in the area has not been adequately characterized with thorough sampling procedures to prove its superior candidacy. On the contrary, geologic information points to its irrational location - unless it's based on markets and accessibility. Although the undermining in the area was not addressed by Gustayson Associates in the report on this application, we still feel that the proximity of these mines could prove to be an easy conduit for any contamination to spread - esp. considering the faulting mentioned by Gustayson Associates. Also, the studies which were relied on for landfill boundaries were not based on any geologic testing. Following are a few quotes from the March, 1975 Amuedo and Ivey study on the Boulder-Weld Coalfield. "Prior to the design stage of many projects, it will be necessary to gather additional information on the subsidence hazards of specific properties. This information will be mainly obtained from core drilling and geophysical surveys, and its acquisition is likely to be expensive."(p. I-2) "Given the above factors, it is estimated that mine limits are within 500 feet of where they are plotted in at least 90% of the instances."(p. V-2) "Factors such as angle of draw, attitude of bedding, and presence of zones of weakness due to faulting can extend the surface influence of a particular void well beyond the limits of the undermined area. Determination of the extent of subsidence at the surface is further complicated by the possibility of significant inaccuracies in the original mine maps."(p. VIII-10) The applicant has changed the border of safety given by the Amuedo and Ivey study. We believe this liberty taken is not prudent. The angle of draw used by the Amuedo and Ivey study was 35 degrees, so we dispute the applicant's supposed throwing in an additional safety factor (p. 30, USR) . The applicant should be required to prove that there is no undermining on the site with systematic patterned drilling. The coal seam mined at the Columbine probably continued on either at a higher or lower elevation at the fault line encountered. Coal seams could ease liquid migration. We question whether the coal seam mentioned in the applicant's report is likely to be discontinuous. Will any natural resources of coal and natural gas be recoverable after the landfill covers the area? The thickness of clay at this particular site is certainly not unique in Colorado. Also, the bentonite clays, with "high shrink and swell potential" as reported by Kip White, deserve careful consideration as a landfill liner judging from their reputation as a road base. This application discusses "hot loads (i.e. ash or coals) in the section on fire protection. Isn't a special permit required to take such a category of refuse? page 3 Why are there no monitoring wells located in the center of the plot going down below the landfill liners? The operator, Mr. Paul Zigan, has no experience in this field that is known to us. We are told his gravel pit operation in Adams County has not been reclaimed, as per his agreement with the county. We would hope you would question his ability, resources and integrity in completing this project properly. With such serious consequences possible, the operator's integrity certainly must come into consideration. Although the idea of the MRF appeals to all, we suspect it as a ploy. What guidelines are followed to ensure health and safety at these plants? The OEC told us the effectiveness varies widely - depending on the operator. The last point concerns the fact that this is obviously a large metro-area regional landfill, as the others in this area are today, and should be evaluated on a larger regional land use scale. Landfills of this size should not be located this close to a municipality on the verge of growth. The Comprehensive Plans of both Weld County and the Town of Erie, as well as other nearby growing municipalities, recognize this section of Weld County to accommodate future urban growth. Clearly, such a goal will never be realized in the midst of landfills. We apologize if any of this information or comments are not pertinent to your consideration of this application. We are not totally clear on the guidelines. We thank you for your consideration of the questions and information we have presented. Enclosed is a copy of a map taken from a report by T. L. Davis and R. J. Weismer at the Colorado School of Mines entitled "Late Cretaceous Growth Faulting, Denver Basin, Colorado" which shows the heavy Boulder-Weld faulting areas. If a copy is needed, we would be glad to supply it. Sincerely, S.E.E. (Safe Ecological Environment) ('Phis group represents Concerned Citizens of Erie and Parkland Estates. ) Board Members: Janice Whalen, chairperson Tom Konetski, vice-chairperson Dick Medenwaldt Marilyn Silver Alternates: Don Brand Toni Salz Other active members of Concerned Citizens of Erie wishing to sign: Marilyn Brand Pat Rice Virginia Blacker S.E.E. P.O. Box 562 Erie, CO 80516 Phone Contact: Janice Whalen at 665-6870 elccy '� /- . ,, . - --'n a w_j,I ; anew n e�.'w / l N Jm V U ii - � e o e / al: i 44. .ill` T ^ a I'r e i\\44\ 0 V ° m I+4\ N `s Kph I i • pegs• ,, Ka I e ! •e ta 'e I e ( . • , e u ,# __ D ia\ Z ° ; ,� P • 1;1f. a If. U, N se �u I I� D /_,• , ) 1, a �a4CO It! Dee ` KII t f!r! f!,. ., p IlD./ .. Kp Ii \icr KII l !/r IMP ++; 131 u \ Tda l _ ,�,: K �.. 1 1 D ) N ' , I. D .. . Du' (......":":"IV A , r r /I i . ,ee i i /r u I�u r Dl MIKK'' _ •- e/ s ' / _ _�_�_W�IJ_County i.I. I •°! / / /- Adams CountyD D / D U D i ,,-, IKm // NII / I a ;VI:, , . Jm CO • 7: 1 e .___ BoulderCounty ` Jet(neon County t kTda \, l u 1r'- [. a a e 1 T Z - Si 2 S \, \ %S 4 ' \ Ky oDa..•' l - 4 - .1 \ `7, e kTda I ' - ., ,/.. —�IMMil=iNNNrine • Figure 1. Tectonic and geologic map of study area. Seismic faults are shown by heavy lines; light lines are major surface faults or faults found in mines. B indicates basement faults. Symbols are shown on figure 2. . 281 . ca fr. •-••_s.‘....:03,..-:,- a 7i.ed 6444.0elo.aAte-cdeuc ei4 We-tit/0c � aitie- d2_,÷49. ��e/fooinx: Zan.orey& act rat tc,. arz) a,ptce itete z/Lat 606:4 rZt 1O1-</c4 VAa4Ac $6 60-c roc) 4y2.coltd ezeedd- -ca-C -44414. /4-:= euteu. ric Gznt ate"` is i y�� cv � 2� zeort an-ctectio'sale . des �A es4,�-cAs`.d°e-�,te a-7,) i&;,A �. ?r- azteL,t tica e, caa-t /suet./ -O-e. rea 0 . 09m .leuteAcooitAt of4,0- 4ce, , � � -� ,a oe cnc 4; ..iiv/.o-66.4.a czAc z-a aatfrk,.7` eo tee. �o-ec-c).a_ae, 6lAk atie _/:ktP&;-o coitscdatoe - a�.e� ,Qc&,,t 2,64.6 � dam. 6,44 / d,& era �� s'� __ [`JI aa2t44;4 eke; cu=re c �o-f,e.oQ� � ,A . o(0<-‘44>cd-63 tee-kJ .1-e, ae,6zweado,_ dakri,t e4 %,-.A, • 7,-.-055` Gaa4c-e, �. 6.n ne a-o can<L) a�.e.zi.e cop-feel) "��ea-te, d a('%1 . " wryfaia-t-oec5-4_,ee- GUSTAVSON ASSOCIATES G E O L O G I S T S • E N G I N E E R S 10 May, 1991 Concerned Citizens of Erie P.O.Box 643 Erie, CO 80516 Attn: Concerned Citizens of Erie Re: Application for Certificate of Designation for Proposed Horst Landfill As requested, Gustayson Associates, Inc. has conducted a study for the purpose of providing a geologic review of the soundness of the proposed Horst Landfill, particularly in light of its location over old coal mine workings. This study has been prepared by the technical staff Gustayson Associates, Inc. Gustayson Associates,Inc., as represented by its principal, Mr.John B. Gustayson, Certified Professional Geologist #2637, fulfills the requirement of"professional geologist" as defined in the statutes of the State of Colorado. Mr. Gustayson's certification is by the American Institute of Professional Geologists. The opinion provided herein is independent inasmuch as Gustayson Associates, Inc. and its principal, Mr.John B. Gustayson, are fully independent and hold no financial interest, either directly or indirectly, in the properties being examined or any properties in the neighborhood thereof. We appreciate the opportunity to be of service and please contact us if we can be of further service in the future. Sincerely, GUSTAVSON ASSOCIATES, INC. Edwin C. MoritzQ� Robert G. Becker • Geologist Senior Geologist ci T 5757 Central Ave. Suite D Boulder. Co. 80301 '3031443-Z209 'ax 13031443-3156 Telex 5101008402 . i Environmental Geology 9 i COAL MINE SUBSIDENCE AND LAND USE IN THE BOULDER-WELD COALFIELD BOULDER AND WELD COUNTIES, COLORADO - Prepared for THE COLORADO GEOLOGICAL SURVEY by Amuedo and Ivey A.R. Myers, J.B. Hansen, R.A. Lindvall , J.D. Ivey, and J.L. Hynes �,c �a tN t b . Ti:. Colorado Geological Survey Department of Natural Resources Denver, Colorado 1975 GUST A"f `Ci 'V*4 1:;8Sn_ r ATF9 , NC usTRA I U U .ae. a `5 F i 1 , '11 1 INTERIM TEXT FOR ENVIRONMENTAL GEOLOGY NO. 9 Fq. The final published text for Environmental Geology No. 9 is 4 currently being finalized and will not be available until mid-1977. Because the text is essential to the understanding of the maps, we are providing this duplicated copy of the basic text of the report as an interim measure. Photographic IL figures in the duplicated copy are of poor quality but will appear as normal halftones in the final version. The final text will also contain a foreward by the Colorado Geological Survey on applicability of the study to HB 1041 with sugges- ' tions for more precise evaluation of the hazard when develop- went of undermined land is proposed. There will also be an t added appendix updating information on the maps at a few loca- tions. Holders of this interim text may exchange it at our 1 office for the final version at no additional cost when it becomes available. M IL ' William P. Rogers, Chief Engineering and Environmental Geology Section Colorado Geological Survey The Colorado Geological Survey is an equal opportunity employer. Sit" 19 ii i 1 TABLE OF CONTENTS Page No . I . SUMMARY 1-1 II . INTRODUCTION AND GENERAL DESCRIPTION OF PROJECT II-1 Purpose and Scope of Study II-1 Location , Size, and Accessibility of Area II-1 Maps and Photos II-2 Previous Studies 11 -3 Acknowledgments II-3 III . GENERAL GEOLOGY III-1 Stratigraphy III-1 Fox Hills Sandstone III-1 Laramie Formation III -2 Quaternary Deposits III-4 Structure 11I-5 Physical Characteristics of the Geologic Section I11 -6 IV. REVIEW OF COAL MINE SUBSIDENCE THEORY AND APPLICATION TO BOULDER-WELD COALFIELD IV-1 Basic Framework of Subsidence Problem IV-1 Subsidence Model IV-2 Subsidence in the Boulder-Weld Coalfield IV-3 V . BASIC DATA MAPS - CONSTRUCTION AND ANALYSIS V-1 Extent-of-Mining Map V-1 Depth-of-Cover Map V-3 Mine-Pillars Map V-6 Probable-Thickness-of-Extracted-Coal Map V-8 Subsidence-Inventory Map V-10 VI . FIELD WORK VI-1 VII . SPECIAL PURPOSE ACTIVITIES VII-1 Photogeologic Review VII -1 Comparison of 1949 and 1969 Aerial Photography VII-4 Low-sun-angle Photography VII-5 S iG,A%..J i 4 ' . TABLE OF CONTENTS (Cont. ) f j Page No . VIII . LAND-USE PLANNING AND MINE SUBSIDENCE VIII-1 Background VIII-1 Subsidence-Hazard Map VIII-3 Purpose and Procedures VIII-3 Basic Assumptions Used in Map Construction VIII-6 Hazard Classification System VIII-7 Safety Factor VIII -10 Reclassification of Subsidence Hazard of Specific Areas VIII-11 Planning Review of Subsidence Hazards of Specific Areas VIII-11 IX . CONCLUSIONS IX-1 X. SELECTED REFERENCES X-1 APPENDIX A City, County, State , and Federal Officials ; Miners ; Local Residents and Others Interviewed During Coal Mine Subsidence Study I Ci4'99 . ' vi 4 yrp� 1 • F( FOREWORD Y ' The problem of subsidence resulting from the undermining { of the surface has received a great deal of study over the past 100 years . Much of this work has been done in Europe where industry, population density, and coal mining tended to grow and develop in the same areas . Damage to surface struc- tures in highly urbanized areas such as the Ruhr and the English Midlands led to intensive investigations as to how to predict where and when subsidence would occur and how to prevent or minimize such subsidence . Until recently most of the signifi - cant research on surface subsidence was done abroad and has been published in journals which are not easily obtainable or are in a language other than English. In Europe , most underground coal mining is done by methods different than those commonly used in the Boulder-Weld coalfield . For this reason , one must be cautious in applying European theo- ries of subsidence prediction to the Boulder-Weld coalfield where the layout and condition of the mines are quite different. In the last decade, land development has encroached on the undermined areas of the Boulder-Weld coalfield , and the impor- tance of subsidence has been recognized . This study is directed primarily toward the problems of land-use in those undermined areas where subsidence has occurred in the past and may occur in the future . Absolute predictability of the amount and area of subsidence in the Boulder-Weld coalfield is not possible with the records now available . t - In Europe land-use plans have evolved to take subsidence into account, and detailed records have been maintained over long periods of time . It is unfortunate that the level of record- keeping in the Boulder-Weld coalfield has not been geared to land- use needs , because the present lack of data severely limits the accuracy of subsidence prediction . Within the limitations imposed by the adequacy of mine data , this study is intended to bring to- gether a body of information that will be useful to planners and geologists involved in bringing the land to its optimum use . I t i I f;14 t iV a S a LIST Of ILLUSTRATIONS 4 _ Figure 1 . FIGURES Following Page Location map Boulder-Weld Coalfield II-1 Figure 2 . Index map of U. S . Geological Survey 7 1 /2 ' quadrangle maps II -2 Figure 3. Generalized columnar section Boulder-Weld Coalfield III -1 Figure 4. Subsidence trough before mining reaches critical width IV-2 Figure 5. Subsidence trough after mining reaches critical width IV-2 r Figure 6 . Stereo triplet of Marshall area V-1 Figure 7. Collapse over room of Marshall No . 1 mine V-10 Figure 8. Collapse area over Lewis No. 1 and No . 2 mines V-10 Figure 9 . Collapse over room of Lewis V-10 No . 1 mine Figure 10 . Recent subsidence over Lewis No . 1 and No. 2 mines V-10 Figure 11 . Large subsidence pit over the Premier mine V-10 Figure 12. Large , well -developed subsidence pits over rooms of the Shanahan mine V-10 Figure 13. Collapse pit over the Allen Bond mine V-10 Figure 14. Numerous subsidence pits above an unreported mine V-10 Figure 15 . Water-filled depression over Nonpariel mine V-11 cr t^ r v vii e- n LIST OF ILLUSTRATIONS (Cont. ) Following Page ( Figure 16 . Broad swale over Lincoln mine V-11 , Figure 17. Broad sag over Morrison mine V-11 Figure 18 . Water-filled depression just east of Russell mine V-11 Figure 19 . Sand dune area one-half mile west of Firestone V-11 Figure 20 . Subsidence over Strathmore mine , South Longmont Street, Lafayette V-11 Figure 21 . Subsidence over Strathmore mine , South Longmont Street, Lafayette V-11 Figure 22 . Front stoop of house to the right in Figure 21 V-11 Figure 23. Subsidence pit at a trailer court in Lafayette V-11 Figure 24. Detail of subsidence pit at trailer court in Lafayette V-11 Figure 25 . Garage over Black Diamond mine V-12 Figure 26. Detail of garage shown in Figure 25 V-12 Figure 27. Damage to VFW hall , Main Street , Louisville V-12 Figure 28. Abandoned building, Main Street, Louisville V-12 Figure 29 . A. S . C. S. photo of area A, south of Marshall , high-sun-angle photo VII -5 Figure 30. U. S . G. S . photo of area A, south of Marshall , low-sun-angle photo VII -5 Figure 31 . A. S. C. S. photo of area B, north of Marshall , high-sun-angle photo VII-5 t, viii „<_” ,k; " _'; ,,,y.E < LIST OF ILLUSTRATIONS (Cont. ) Following Page Figure 32. U. S . G. S. photo of area 6, north of 't_ Marshall , low-sun-angle photo VII -5 s DRAWINGS (In Pocket) • 7361 -1 Extent of Mining Map 7361 -2 Depth of Cover Map 7361 -3 Mine Pillars Map 7361 -4 Probable Thickness of Extracted Coal Map 7361-5 Subsidence Inventory Map 7361 -6 Subsidence Hazard Map tr,�, f-, - I .! SUMMARY - r, t r I , ' This study is intended primarily to provide basic data concerning mine subsidence to local and state planners . It is • also intended that other investigators preparing more detailed _' studies of specific areas can use this data. The project is not an exhaustive treatment of mine subsidence . Rather, it focuses on basic, subsidence-related problems and on practical approaches to land development in the project area. The purpose of this study is to define the extent of mining as accurately as possible , commensurate with the scale of the final maps , and to define the physical factors controlling sub- • sidence . Such factors include the extent of pillar removal , the thickness of extracted coal , the depth of cover above mine : .. workings , and the times of mine operations . The scope of this study is confined primarily to a review of existing data , a limited amount of field work, and the pre- paration of this report. Maps , tables , and photographs illus- trating the findings of the study are presented . Techniques such as low-sun-angle photography and aerial photo interpreta- tion have been examined as possible tools to be used in subsi - dence studies . i The most important product of this study is a subsidence hazard map which shows the degree of subsidence severity which 01 r. a....- _ .. .. I-1 4 I Figure I t{ 70W.-49 r ' i a FCB�•W.{s I.. a "' ;r a I p P• I —I . . banglgo f. 1 'Li. t'' `i.I , t, r_ - Y• may( s r:f1M1. �G.....I.s +••� I I) ,:.^ , 1U <1 '. , P A. al..' I 1 T u. ,� w� �`, `,I ,.� ,J F , j ,r ', `` r N. }�� I r � - {E ( , r. .a..o / * I P.y \ �7 �I/ x flop 9 II �• r. 4. ..." L" ,fr n .if -. �I( 1 , ,, 4-. . .L)s I I . � . P' �. 'It...•� Id.01 _. T_ 1. 1 . •; f 1y�� jj �I l •�'h„t Ire 1 i L " """ mot•►. `,�"� I'' '� } f + ' •� s f , fiesta sa ` • • : I qya.1 'a R Y r r �o • �_ G .~� I Ai fER-ON GO<rIM la C,('T', : ..a� _ < / / _ _ 2 ". ~'/ p \\ .. I _ 1'C '-, .•` A'''',.: \ . ...-. alec . .viie.•...AL; / is u. - I �t c..ey J I � �. , ` ' f f i HOC%1�MUUN:AIN. ,...I - I M. .a l �.. 4kS`IU,1 ,� • I — — i,. �_ �. T. • I•. w ��10 S lam # / 3 u _ _L,,,r �� :fir„�_ s i I \ / El :e,kt f — Vdl1P Ofi Ridge I .w,.. Golden _ 11 -"� :" •® � �� •l 4 •v 1114 �"��' _• _- NV Ft "'i �. "— i U- l 1 I �, *1� . ' \� I 1r,F.,e f"— yt I 1 „...- " ,.Oxav,wc 9ws1. LOCATION MAP BOULDER —WELD COALFIELD it , °1 A;,r31 Yr''. '» y . can be expected over the various undermined areas . State and local planners and land developers will find this map particu- larly useful in making initial judgements about the feasibility of projects within the coalfield. Prior to the design stage of many projects , it will be necessary to gather additional information on the subsidence hazards of specific properties . This information will be mainly obtained from core drilling and geophysical surveys , and its acquisition is likely to be expensive . It is believed that, de- spite the increased costs and problems brought on by undermining , development in the Boulder-Weld coalfield can be undertaken pro- vided that good design and planning practices are followed . Y i Crl TA I-2 4 I Ant Fa II . INTRODUCTION AND GENERAL DESCRIPTION OF PROJECT Purpose and Scope of Study i The purpose of this study is to delineate the extent of mining in the major portion of the Boulder-Weld coalfield as accurately as possible and to define the physical factors con- trolling subsidence in the area. The scope of the study was confined primarily to a review of existing data and to limited field work . It included the preparation of this report and its accompanying maps, which summarize and illustrate the findings of the study . This report is intended to provide basic data to local and state planners and to other investigators preparing more de- tailed studies of specific areas . A comprehensive discussion of mine subsidence and related problems is beyond the scope of this study , which deals with the special problems of a limited area. Location , Size , and Accessibility of Area The Boulder-Weld coalfield lies in north-central Colorado about twenty miles north and northwest of Denver as shown in end Marshall Figure 1 . The study area extends northeastward from a (four miles south of Boulder) to just north of Firestone , two miles east of Interstate 25 . Approximately 160 square miles were studied . The area includes the southeastern corner of u I II-1 S 173.1 t ..:(1s �, .< - $). . i ZS�. 1 , } .Boulder County, the southwestern part of Weld County, and the II ` '!northwestern tip of Adams County. • 11,1 iia i Accessibility throughout the area is good. Interstate 25 r IF, allows ready access to the northeastern half of the area, while t i ",", :, the Denver-Boulder Turnpike provides access to the southwestern . . half. . U. S. Highway 287 runs north-south and Colorado Highway 7 runs east-west through the area . In addition to the paved major- highways, there is a network of unpaved roads throughout most of the study area . As a result, there are few points which are more than a half mile from either a paved or unpaved road . {I : Maps and Photos The study area is completely covered by U. S . Geological Survey topographic maps (Figure 2) at the scale 1 "=2000' • , (1 : 24000) and a contour interval of 10 feet . These maps are j recent and vary in date of publication from 1949 to 1967. They , . were subsequently photo-revised in 1969 and 1971 , and it is the revised editions which were used to construct the base maps for --this report . ', Aerial photography of the area, taken in 1969 at the scale 1 "=1667 ' (1 : 20000) , was obtained from the Agricultural Stabili - zation and Conservation Service (U . S . Department of Agriculture) . . I During the course of this investigation , specialized low-sun-angle aerial photography was made by the U. S. Geological Survey. These photos were taken in the summer of 1974 and covered a few limited - o f;619 A II-2 .#: Figure 2 W - II zg ^c....... • '� I \r ' I 9! �., 1 1r T t is: `10 ,f 'V Ci r - ^ +`,, .-i \off0 t ` ".•.�� 1 .. } 1 \ ^Y It .. r _ .. • l n��. \\/ •Ygoo •ro:1 .. 1 C ,:C PI Jinn Lit fr - : I n sd A•* F ( " I ,I • �` at tJatlr�l :��N SJ c : a •I ff 6 t -1 Q-• .v y' 1` _ . ,�+'`•I'f ,, „ c q'>i 16. .1 • , 7 v j.5,..:.� ..? - • .. d2)1 . /LC 2,,r, C''. 9/4 je el 4'41 ,\/ .C;rl t 1 VII 5 1� 1� LLL •':alS' Nt ll`•SG• ,••c —) 1. r✓+r _. '5..91 ^ f. "..air I 1, tildef !�T�— • I�.11A.• .1 r i v a e. - f J i r 5 � 1 / T/. MK ) . . ll"�''(� ' _ t (19ZtI3 I ' 143,-69,1 ►^ r, f re srin,o- l seas �'c p 1 Br {V _ '.•••CT . 4,/e _ I /OBIbFr l.wlvr. / �� 1 fkt I ��Oi� ` • +�., 15.•.Vi 41 �.' fY BOULD R CboN r .% oomi Id ..�. H. r •.� , - —' _ a AMP Off COL) Tr • \ V5F. 1, - , / - + '' ,� f yiq• I C -.� Jen es Cs w. + J (.. qC p Rocky Fie. /CZ'I-I\ '/ 5/aJ� 1985 (1 , 1 I (1371) I = # 7 •� , -t -T .• c NCR'if — --k---1-; �- M ..? ....Y ,� / On i �• 11/4s, O- `• 1 -x— v 14 ws 1 CO •y ^ t 1�• . i ,I 1 O"eai; •i. I�W mirnher • D' t .. u ,.., I: '1 • Ii ._ • A., • t —• � _ ( / AOCAN•YO11NI41i1.}._ I b ARSENA41 ' 11 . 1I.Io "' `. - R .. I 3 / NOIre r.6�f f MOUNrave. �I .., F +9' 1 /A�� t - S. • - (Whea Rid a RN�• •� Golden _ � 9 _ I „ ® e r�. , - . scut= • •:•-b. ■ �� MOU • MT ovo NT f 7eee r - ` n.mo 8t. llwi. . w i :1 I. ^�'� i ✓. [11'�i�► N :: ' t kpa'\� 1 Dari. ":7,7-b. . 1 .C 1 1. i w i "'`L>SWR7aAF �A5E a. INDEX MAP OF U.S. GEOLOGICAL SURVEY 711' QUADRANGLE MAPS Map published 1965 Map photorevised (1971) cy �;�� 21_ _ .';1...9 �4 , a; wi areas where there appeared to be subtle subsidence depressions . It was believed that the long shadows cast while the sun was low I. Y 7 in the sky would enhance the recognition of the depressions . The Geological Survey consented to our review of this photography and furnished copies of it. Previous Studies IThree previous major studies of the coal mining industry in the Boulder-Weld coalfield have been made. The Colorado School of Mines Foundation ( Grosvenor, 1964) compiled and published a study which showed the location and extent of mining in the area . In addition , the U. S. Bureau of Mines ( Lowrie , 1966) published a study of the coal mining industry in the Boulder-Weld coalfield which included a map showing previous mining in the area . This map was updated and revised (Colton and Lowrie , 1973) , and pub- lished by the U. S . Geological Survey as a map showing mined areas i of the Boulder-Weld coalfield . MAcknowledgments Grateful acknowledgment is made to the Colorado Division of Mines which made coal mine data and individual mine maps avail - able for use in compiling the maps included in this report . Thanks are also given to Roger B . Colton of the U. S . Geological Survey for providing mine maps and information concerning the coalfield and its geology. The U . S . Bureau of Mines kindly t { II -3 2 1.'-S 5 f1 i I ; , prepared microfilms of unclassified mine maps for our use . Per- sonnel of C. S. Robinson & Associates provided helpful comments on general subsidence problems in the area and allowed us to re- , view certain maps and core-hole information which they had pre- pared for some of their projects in the area. Mr . D . L. Scroggs , formerly with Amuedo and Ivey, was of great assistance during the initial stages of this project. Finally, special thanks are ex- tended to the various city and county officials , residents , and coal ,miners of the area (see Appendix A) who gave their time and I supplied useful information for this study. 4 : I . 4 • cry A19 i II-4 • III . ._ GENERAL GEOLOGY V' a ryri Stratigraphy • = y Two bedrock units, which dip generally eastward into the ' Denver basin, occur within the area. The Fox Hills Sandstone and the Laramie Formation are both of Late Cretaceous age . The Fox Hills crops out extensively in the vicinity of Marshall but in other areas is covered by younger deposits . It is conform- ably overlain by the Laramie Formation, which contains the coal - beds mined in the Boulder-Weld coalfield. Outcrops of the Laramie are rare in the area because of extensive Quaternary deposits of colluvium, pediment gravels , and wind-blown mate- rial . The colluvium is ubiquitous ; the pediment gravels are most widespread in the Marshall area; and the wind- blown depos- its are common in the Frederick-Firestone area . The general character of the bedrock and unconsolidated units in this area , is summarized in Figure 3. Fox Hills Sandstone - This formation is a massive , crossbedded , and ripple-marked sandstone, which is in conformable contact with the top of the underlying Pierre Shale . The lower two- thirds of the Fox Hills is fine- to coarse-grained and slightly ' calcareous , while the upper one-third is fine- to medium-grained and crossbedded. The thickness of the Fox Hills ranges from 60 feet to over 300 feet and appears to have been controlled by fault movements contemporaneous with deposition . 4 firSIM III-1 Figure 3 , �, fliemATION5 AND GRAPHIC 1e1CICKS5 OISU 101104 Olin. %USOl VISIONS 111x0106, m`V (It.l , '# ( "• St I 90A1t 4444♦ SO4f ICIAL >.g:ci`.- co 0-s0 Italian 44444 its and pediment graaais DEPOSITS J'OC4:- e'- L u1L ~, 600.100 Clystone, shale. sandy shale and lenticular i eels o/ sanNstone And lignite - _.- -------- 150.190 2 1/2-S Coal, occurs aporaa idol'''. of limited Coaleee Nn. 1 lateral enfant —." . -..+ s 95.14$ Shale, sandy shale -^ i. lialtigi <eolerd eta. a SS-120 2 I/2-e Cain, lenticular. nenpenl+tent 1 Conlbe iea.-1 2045 Shale, sandy shale, or aanas tone ,_ I Coaleee Se. S 15-00 2 1/2.10 Coal, range+ over a vide aru, but Is Iaatacola, 1'Nl as le Sego') 1-16 Shale, sandy shale or vnas tone -o �r --i 2-1 Sandstone, white to llg4t•gray 1•S Sa nattone, M1ha ly, whi Ll. ` 'P Sandstone 4.10 . white. -grained cencretlonaret . case haraanaa ripple marts at top { - 0-15 Shale and friable sandstone itL Coal• lenticular, discontinuous. found mostly Coaleee no. 4 ® 1-15 2 1/2-11 in central and toutaaaaaarn part o1 field 1-15 Shale. may pinch se Coaleeds 1 and a caalaace (Wised See 1 0 0-14 Coal. very bright. resinous contains 1'.o nu. Seem- small very amount 01 prate J-10 Sandstone, white, fine-grained, I llgnitic, shat?, ouartaose , Coaleee no. 2 1-12 Shall, brown to gray, ligmitic; Contains ('Sump Stem-) 10-K 1'-/' coal eta near the base y ° 1'+ a� IO Sanastone, white, fine-9ralned, than- •N- Sandstone .:[,-. some lignite and iron stains 1. .�.';.'....,.. 'r r - .. •-, .Ante. brown-t talnN: ;(f:a:2s.:-• 4-0 Sandstone• laterally to sand? shale - ]-6 Sandstone• aroma to buff. contains pelecypods 1.11 Sandstone- light tray. mottled with yellow. hard, fine-grained. geartaese d5 1-1 Coal. thin, non.ar414tent. Iraaea laterally Coe lees na. IMIMI Into Carbona cocoa shale 1.1 Shale, pa? to .lack, carbonaceous l0 stoat,"'"""': '' "' Sandstone, 9reemlah buff• line- to coaaaa- •v.Cva/'+.l'5.I"'m f0-100 gra anaa, C rust•beeded; guarttese in Ewer f0i 1411.1S SANDSTONE :. :'•:::..:::::: gfe-g upward to light )aayell., aaa ig ' white fine-n!• to Nelum-Ira 2ned iand4tone I. GENERALIZED COLUMNAR SECTION BOULDER -WELD COALFIELD =.'�.�ii3'? 3 s Laramie Formation - This unit conformably overlies the Fox Hills Sandstone and is divisible into two parts . The lower part, which a =y ' varies in thickness from 80 to 125 feet, is composed of sand- ' ` stone , claystone, clay, shale , and coal . The upper part, about 4 . a ,. 600 to 700 feet thick, is made up of claystone and sandy shale with some lenticular beds of sandstone and coal . The total thickness of the formation ranges from 600 to more than 800 feet. Seven coalbeds of minable thickness occur in the Laramie , and they are numbered , from oldest to youngest, in ascending or- der . Coalbed No . 3, known as the "Main " or "Gorham Seam, " has been the most extensively mined , and is the most widespread coal - bed in the field . In certain localities , such as the Imperial mine , the bed attains a maximum thickness of 14 feet. Because Coalbed No. 3 is the most widely distributed unit in the coal - field , it is used as a stratigraphic datum to which coalbeds above and below are referred. 1 . Coalbed No. 1 and No . 2 are thin and lenticular , and u have no known mine workings within them. Coalbed No. 1 lies at the base of the Laramie and is- about 65 feet below the No. 3 bed . Coalbed No . 2, also called the "Sump Seam, " lies 10 to 45 feet below the No . 3 coalbed . 2 . Coalbed No . 4 is 1 to 35 feet above the No. 3 bed . In the Marshall and Lafayette districts , Coalbeds x III-2 s i No . 3 and No . 4 coalesce to form one bed as much as 12 feet in thickness . This combined bed has been mined extensively in these two districts and in the Columbine mine. ' 3. Coalbed No . 5 , locally called the "Middle Seam," is 35 to 80 feet above Coalbed No . 3 . It has been mined in the area west of Firestone and east of Dacono . 4 . Coalbed No . 6 is known as the "Upper Seam" and is 55 to 120 feet above the Coalbed No. 3. The bed I I has been mined east and northeast of Erie by both underground and strip mining methods . 5 . Coalbed No . 7, the uppermost coalbed , occurs 150 to 190 feet above Coalbed No. 3. Because the bed f is thin and very local in occurrence , it has not i been mined commercially. The complex geological conditions of the area , namely, un- even erosion and deposition along with intense faulting and related folding, make- correlation of the coalbeds difficult and in some places doubtful . In a recent study, Weimer ( 1973) has suggested that the 11 J sandstones of the Fox Hills are a delta front deposit and that � I M t• III-3 6-n k. s ' the sandstones , claystones , shales , and coalbeds of the Laramie Formation are a delta plain deposit. Unequal rates of deposi - tion caused by shifting channels within this deltaic environment - 4v produced lenticular coalbeds and lithologic units of highly ` j variable thickness and composition . Fault movement contemporaneous with the deltaic sedimenta- tion also affected the depositional patterns of the two forma- tions . This "growth faulting" allowed increased deposition in the graben areas as these fault blocks moved downward , while deposition over the horst areas was reduced. As a result, vege- tal matter , which later formed coal , accumulated in greater ; thicknesses in the grabens than over the horsts . Quaternary Deposits - During Quaternary time , streams descending • from the Front Range deposited a series of pediment gravels along the mountain front . The Rocky Flats , Slocum, and Verdos pedi - ment gravels cover the Fox Hills Sandstone and Laramie Formation south and east of Marshall . Recent aeolian sand dunes exist in the vicinity of Frederick - `. ::n and Firestone . The sand is derived from the floodplain of Boulder Creek, which lies to the northwest . The depressions as- sociated with sand dunes and those created by wind scour (defla- tion) are easily confused with depressions caused by surface subsidence . Colluvium and soil derived by Recent weathering of the nonresistant Fox Hills and Laramie Formations are widespread throughout the project area . III-4 { Structure The study area is located on the western flank of the Denver basin . Regional dip on this flank of the basin is gently east- southeastward through most of the area , and regional strike is approximately north-northeast. The north-south trending axis of the basin passes through the Frederick-Firestone area . The study area is complexly faulted into a series of narrow 1 horsts ( upthrown blocks ) and grabens (downthrown blocks ) . These M 3 fault blocks average about five miles in length and are from 0 . 5 i to one mile in width . The trend of these structures is generally about N10°-20°E, and this is superimposed on a regional fault trend of N45°E. Beds in the grabens and horsts are folded into synclines and anticlines , respectively. Offset on individual t faults may be as much as 500 feet, but the average offset is only i about 200 feet (Spencer , 1961 ) . Movement along the majority of the faults was dip slip . Faults with large displacements are natural barriers to mining and therefore define the limits of many mine workings throughout the Boulder-Weld coalfield . The faults are not obvious on the surface . Their recogni - tion is based , for the most part, on subsurface data obtained during coal mine mapping and from core holes drilled during coal exploration programs (Spencer, 1961 , Lowrie , 1966) . During the present work , it was not possible to verify, either on the ground ' or on the aerial photos , the accuracy of the fault mapping done by previous workers . The faulting shown on the map by, Colton and • III-5 c*i ' ^v"� b • Lowrie ( 1973) was adopted for this study with only minor changes . a > A few small faults shown on maps of the Baum and Boulder Valley No. 3 mines were added to the base map prepared for this report . iX It is believed that there are probably more faults within • the study area than have been shown on the present and previous maps . Many of the faults shown on these maps are known only from underground mine workings . It would be expected that an equal number of faults would occur outside the areas of mining but, owing to surface cover and lack of subsurface information , these faults have remained unrecognized. Physical Characteristics of the Geologic Section In the Boulder-Weld coalfield all of the mined coalbeds are within the Laramie Formation . This formation is composed of interbedded shales , claystones , sandy shales , coalbeds , and thin beds of sandstone . Generally , such rock strata are incom- - J petent with respect to stresses induced by underground mine operations . If left unsupported they are subject to fairly rapid collapse after mining. Local coal miners who have worked in the Columbine , Washing- ton , Eagle , Imperial , and Hiway mines report that while the roof- stone of these mines is prone to collapse , an " ironstone" layer occurring 12 to 80 feet above the mine workings tends to stop further upward caving. This ironstone is one- to five-feet thick and may be the quartzose , concretionary "C" sandstone S fit'1;141 III-6 ,l i described by Spencer ( 1961 ) . In the past, the ironstone cre- ated problems wherever it occurred immediately above the mine workings because of a tendency to bend rather than break. The -. bending created a "squeeze" on nearby pillars of coal and made it impossible to mine them safely . The floors of the previously mentioned mines were soft shale or clay, and a "squeeze" on the i pillars was sometimes relieved by a "heave" or rise of the i adjacent mine floor . It is possible that the resistant ironstone layer has pre- vented caving from reaching the surface in areas of the Colum- bine , Washington , Eagle , Imperial , and Hiway mines . If so, voids or uncompacted rubble may remain beneath these areas . Similar conditions may exist over other mines of the area as well . The material that forms the floor of a mine also plays a part in subsidence. A hard sandstone floor might support a standing pillar of coal, while a floor of soft shale or clay ( underclay) would allow the pillar to sink . The sinking would continue through the thickness of the soft material and would cause subsidence of the overlying strata. Soft shale and clay floors are reported in the Baseline , Columbine, Eagle , Eldorado, Hiway , Imperial , Industrial , Monarch No . 2 , New Gorham, Para- , mount, Pluto, Standard , Vulcan , Washington , and Witherbee mines . Hard sandstone , shale , or "slate" floors exist in the Black III-7 F.41361.,.9 61. "{^�jJ Diamond No . 2 , Boulder Valley No . 1 , Evans , Puritan , Shamrock , and Star Mines ( Lowrie , 1966) . It should be anticipated that mines with hard floors and standing pillars may have a greater percentage of remaining void space than those with soft floors . I r a r -i+ . a;:::?:i:i ;. ;." ,. { fi III-8 IV . REVIEW OF COAL MINE SUBSIDENCE THEORY AND Y - APPLICATION TO BOULDER-WELD COALFIELD Basic Framework of Subsidence Problem i The basic questions asked with regard to subsidence are I few in number and seem deceptively simple to answer. Given an underground opening of known vertical and horizontal dimensions , t one wants to know: 1 . How much vertical subsidence will there be at the surface? I2. What will be the lateral extent of surface subsidence? 3. When has (or will ) subsidence occur? 4 . Has the process of subsidence been continuous from beginning to end or has it been episodic? i Generally , the subsidence theories used to answer these t questions are based on the assumption that extraction of coal has been complete and that a continuous unsupported void has been created. These conditions do result where longwall mining meth- ods are utilized, as in Europe. However, in the Boulder-Weld coalfield , mining was done by the room-and-pillar method , and the underground conditions created cannot easily be made to fit Euro- x ._ pean subsidence models . It is not within the scope of this report ;II to go deeply into the many facets of subsidence theory , but a re- view of certain aspects is timely and may be beneficial . For more detailed descriptions of subsidence theory the reader is IV-1 .# vr,7.5 f'141 • referred to a recent work b Zwartend ck 1973) . This y y ( publica- tion "gives a thorough summary of the development of subsidence theory and contains an extensive bibliography. N ff Subsidence Model \. Y Modern attempts to relate surface subsidence to underground mining make use of the concept of the subsidence trough. The concept takes into account one of the most important observed facts regarding subsidence; namely, that the surface area af- fected is larger than the mined-out area . Because the concept can be diagrammed, it provides an easy way of looking at, and describing, subsidence problems . Figures 4 and 5 illustrate diagrammatically the development of a typical subsidence trough . The extraction of coal removes support from the overlying strata causing them to sag into the void space created . The sag is propagated upward to the surface , i and, it follows , that the maximum surface subsidence can be no greater than the thickness of the coal bed mined. However, the lateral extent of subsidence at the surface is greater than the • extent of underground mining. The surface position of the bound- • ary between areas of subsidence and no subsidence is defined by • the "angle of draw. " This is the angle between a vertical line and a line drawn from the point of zero surface subsidence to the edge of the underground opening. The angle of draw varies A S� C.'t3 a,:,2 R IV-2 .:_ . t i . , • _� b to ab <AB dw ..d • _ , � ' oL = Angle of draw I A A . e' a 24 1 ( - I a 1 Direction of Mine Advance . Subsidence Trough before Mining Reaches Critical Width I II Figure 4 As a mine face advances from point 1 to point 2 the i surface subsidence which occurs will take the form of a shallow I ( I trough , shown as curve aba. The greatest amount of subsidence ' j for a given width of mine opening will be equal to ab and will ` be located over the center of the opening at b. The amount of Isurface subsidence will diminish on either side of b until , at points a and a, it is nil . Since as >AA' it can be seen that Ithe area affected by surface subsidence is greater than the mined out opening . Subsidence ab will never be greater than !I AB and will in fact be less than AB until a certain . "critical I width" of the mine opening is reached. The line aA connects I the point of nil subsidence and the edge of the mine opening and forms one side of the "angle of draw. " In British and American literature this angle (d) is measured from a vertical line; in European references it .is measured from a horizontal line . II 1 Sitin <N. ^• d. 4J `; R): � ., 4 it; { X(re . _ Y ' . 7G: r .. a slX ✓. d ab=Smax CAB of=Angle of draw • A Critical Width A B 8 °Subsidence Trough after Mining Reaches Critical Width Figure 5 As the mine face advances , ab and angle cc will increase until a "critical width" of the mine opening is reached . At this point the amount of vertical subsidence , ab, reaches a maximum value , Smax . Further enlargement of the mine opening will subject a larger and larger area at the surface to maximum subsidence though Smax itself will not increase . In three dimensions the deepest part of the subsidence trough will change from an axial line , as would be the case in Figure 4, to a flat bottom as shown above . S Y i , i from 25° to 35° in most instances . The larger the angle of draw, the wider will be the zone on the surface in which sub- sidence should occur. By using the largest of several possible angles of draw a greater margin of safety is established for i j those areas lying outside the boundary of possible subsidence . Subsidence usually occurs gradually when it is concurrent awith mining . After cessation of mining, subsidence may continue to occur in a steady, gradual manner, or it may stop for a pe- riod, to be followed by failure at some later date. In some European mining districts , sufficient information has been col- lected so that the rate, amount, and direction of subsidence can be effectively controlled . In order to accomplish this , much basic information had to be gathered , and special mining pro- ! grams had to be designed. Subsidence problems are much more difficult to solve in areas where mining has occurred in the past, and where records do not include the data needed to devise means .of controlling subsidence. This is true of areas which have been mined in the past in the Boulder-Weld coalfield , but it need not be true of areas mined in the future . - Subsidence in the Boulder-Weld Coalfield In the Boulder-Weld coalfield , the usefulness of the subsi - dence trough concept is limited. The model on which the concept j is based is an underground opening which is unsupported and free 11. E 1, [ j IV-3 i it to collapse as the mine face is advanced . This is the common condition in Europe where the longwall method of mining is used; in the Boulder-Weld coalfield the room-and-pillar method was L used almost exclusively . Even though it was common practice to remove the coal pillars after the rooms of a mining panel were fully developed, it was not possible to recover all the pillars . Some were left to protect main shafts and haulageways ; others were left because they could not be mined safely . The pillars which remain in the mines continue to support the roofs of under- ground openings and prevent subsidence troughs from developing in an orderly and predictable pattern . Depending on the number, dimensions , and distribution of pillars which remain in a mine , the width of mine opening could be kept below the critical width for that mine, and subsidence would be prevented from reaching its potential maximum. Surface subsidence would remain below this maximum until the pillars finally gave way sometime in the future . ir , y a 1'i61l 9 a - IV-4 V . BASIC DATA MAPS - CONSTRUCTION AND ANALYSIS ( Extent-of-Mining Map This map delineates areas of coal mining in the Boulder- w, a Weld coalfield and thus , partly defines the limits of mine sub- sidence hazard . Previous work on the extent of mining in the coalfield was conducted by the Union Pacific Railroad . Company ( 1964) , Grosvenor ( 1969 ) , Lowrie (1966 ) , and Colton and Lowrie ( 1973) . The extent-of-mining map refines the boundaries of the coal mines as shown on earlier, published maps , and shows the differences which exist between this study and the, work, of IColton and Lowrie. This map was compiled by visually reducing the outlines of J individual large scale 1 "=200 ' ( 1 : 2400) mine maps to a scale of i ' I 1 "=2000 ' ( 1 : 24000) . Most of these maps are on file with the � ( Colorado Division of Mines , some are in the microfilm collection of the U . S . Bureau of Mines , and a few a`re in the collection of Roger B . Colton , U. S . Geological Survey . In some areas , air photos and field observations of subsidence were valuable in re- defining the extent of underground workings and in determining the existence of several mines which had not been plotted by previous workers . Such areas included the Marshall #1 , Marshall j #3, Fox, Black Diamond , Old Black Diamond , and Allen Bond mines , mined areas around the Blue Ribbon adit, and an unknown mine in ' SE 1 /4, NE 1/4, sec. 18 , T . 1N . , R .68W . (Figures 6 , 13 and 14) . 0113619 i -4=-2,i4- F• i .:♦ �y ce, : _ r . ,q�y ! ��. T t 1 > r i Ja %w_'k C m ++ +.. r 4, „J:11.1%; it, � T ^ d �L 4 ! �? - - J. '1 oc mxvo "y�" L •r C c C/ 7 V, i J., 4 , * f J' rA C N 7 i-r 1... ..-- Y +1 CJ VI T ro E e0 ro L T•- 'x '� 1 4 x t ..b x . C 4- •r N > F ! r 0 >.,.... N L v 4-3 a) CJ Or 7 (-1 G y CCC `` Y dig y rCma+ w U1' Z.' , ' ,./2.‘‘,411 .y . Aduyi 3 " 7 L ++ v v Ci T ‘ ,err*"‘;‘,1*, 1+Y 1 * l ` R lr, O^.Y A ^ CJ C) al c i r ":.'y v ,r 0¢74.4-It P*tM •Y 7 -. .r O N O. •r s- N 4-) S.• r• x , • L n. a), VI r0•,MI I t�ep{ C CU tts'• P a` Y +1 .. N r0 U 4. J / r� , O Cl w O L N O O CU Y" e ^ r �4 r°` �c:. N], r c O O CJ S-••-• C11-0 in su rf v**et' y+� e r,ax <'^` 7 Cl 4- ^ 01 c N =T111 ;if 11' A1 r' <� ♦ f ;.� • O 7 U O •r L c >� i t !! �§ i,R{f .may +nra,; t0 U 7 C C E +� 7.--� ��'`,�_� ' `�i Y:..� `� fit' CJ s- us as WOW O. g- I i `..,. :7 ()T 07.—,r Rh Y �' y {.e .l. ra al d r" = lJ LL_r•ill ft • "�\" . q.. rn n.s c n E r - r . fai— tJ�/+s • r "/:i .a" °1*..•t 110.1.101„. .-t "� r O +> �4-, Cl U + f .r.' s ipp S 2,•9-n' w �r'".�_�. w +, . C O•r ._ J , 4.� - k {.. *I.de r .r O b ^ Vt O 0_N a-1 sttitilt r ,y�� d Icy.• 1 + !• ^"'J' dJ ^ C) g— 7 C u, U c t.yy�4�x'. / i 4"C+•" . :s^ .?r E. d CI MS OS 3 N O F 'x,41 - 1- ' `T•' a • 4 •r L C)'0 L i 0]O {J • d-, L CJ c 4-'0 N ~ � tl O 4- c U 4- Ca- r0 r + > fi • p vvvc v a. ‘14 .IWit r i v r 7 r 1_ �� • t0 VI Mg— C II 1 y • Jr/ d' y rF. f 3... �.' 'A'�K r'Ktr.•y p _ t0 i Cl Cl •r"0 r—4O-�{ eS^ F,yc `t}� i,� L di c •r L.-• N �,,,,Yy .`• a a N L N rCI C Id „�'• •I.WP - r�s .""1-.C `,,,ti ' '-�' ' .,-.�, '^''�.r •r s L 7 d 4-v •r U sn r4M' I r .pp ?:5 • e fir' ,1 Y Q i The reliability of the extent-of-mining map is dependent upon several factors . First, it is limited by .the accuracy of the original mine surveys . Post-1920 mine maps appear to be more carefully surveyed than earlier ones , which may be mere sketches of the mine layouts . The earlier maps may also lack accurate reference to the land surveys shown on surface maps . I Second , many of the smaller mines and some of the earlier mines have been recorded with the Colorado Division of Mines , ; but no maps exist for them. Third, areas of "chiseling" or "poaching" of coal are not shown on the mine maps . The coal removed in this unauthorized manner was usually taken from the barrier pillars between mines . Although the problem has diminished in r recent years , miners can point to areas where coal has been l poached as much as 200 feet beyond mine boundaries . Some miners feel that wherever royalties are being paid on coal ex- tracted , poaching is common , and thus one might suspect inac- curacies in even the more recent mine maps . Lastly, it is evident from an examination of the only available maps ^of some mines (eg. Red Ash-Pittsburg, Marshall No . 1 ) that the maps do not show the maximum extent of mining. In the case of the Fox mine , surface collapse features show that the actual limits of mining extend beyond the boundaries shown on the mine map .' Given the above factors , it is estimated that mine limits are within 500 feet of where they are plotted in at least 90% of the instances . I V-2 i Y' 4i. Discrepancies which exist between this study , the Colton and Lowrie study ( 1973) , and the Lowrie study ( 1966) are gen- erally differences in the limits of the mine boundaries and may be accounted for by differences in plotting techniques , or by the utilization of different mine maps . Some of the more impor- • - s tant areas of discrepancy are : 1 . A small mine north of the Fireside (NE 1/4 , sec . 7 , T. 1S . , R .69W . ) 2. The area west of the Acme mine (SW 1 /4, sec . 8, ar T. 1S. , R .69W . ) 3. ' The area northeast of the Vulcan mine (NE 1 /4, sec. 10 , NW 1 /4, sec . 11 , T. 1S . , R. 69W. ) 4 . The area east of the Imperial and Eagle mines (SW 1/4 , sec . 11 , NW 1 /4, sec. 14, T. 1N. , R .68W . ) 5 . The southeast side of the Puritan mine (SW 1 /4, • sec . 2, T. 1N . , R .68W . ) c 6 . A lobe of the Lincoln mine (SE 1/4 , sec. 24 , T . 1S . , R . 68W . ) 7 . A mine south of the Witherbee-Peerless complex (SW 1 /4, sec . 4 , T . 1N . , R . 67W . ) . ill . This study , utilizing the available mine maps , and to some C. extent, interviews with residents and miners , could not confirm "lhe 'existence of mine workings in these areas . • Depth-of-Cover Map The purpose of the depth-of-cover map is to show the thick- ne`ss `of overburden above mine workings . To simplify the over- burden thickness determinations , a 50 foot contour interval was used . x'61() V- 3 In obtaining the depth-of-cover values , it was necessary i, to determine the elevations of the mine workings . When avail- able , this data could be taken from individual mine maps , from records of shaft depths as reported to the Colorado Division of Mines , and from drill -hole information of the Rocky Mountain Fuel Co. With this information , a structure contour map of the top of the extracted coalbed was made for each mined area . A surface topographic map was superimposed on this map, and struc- ture contour values were subtracted from surface contour values . The resulting overburden thickness values were plotted to the I � extent-of-mining base map and were contoured using the 50 foot interval . For mined areas with multiple seams , the overburden above the highest mining level was contoured . The main problem involved in determining the overburden thickness is the lack of elevation data on many mine maps , es- pecially pre-1920 mine maps . In such cases , drill-hole data and shaft-depth records were utilized as an approximation of the depth to mine workings . If these data were lacking, an es- timation of overburden thickness was made by 1 ) extrapolating structure contours from adjoining mine workings where the same coalbed was being mined , 2) interviewing residents who had 7 drilled water wells into the mine workings , 3) interviewing { miners who had worked in the mines , and 4) relating the charac- { , 1 ter of subsidence in the unknown areas to the character of I { , r k i f � �. X subsidence in other areas where the overburden thicknesses were known . In all cases in which only one data point was available , the coalbed was assumed to be horizontal , and overburden thick- ness was determined accordingly . The data available and the 1 X method used in obtaining overburden thickness determinations for 1 different mined areas are shown on the map . The sources from which mine data were obtained generally gave elevations to the nearest foot and in some cases to the nearest 0. 1 foot. Considering the 50-foot contour interval used , the depth-of-cover map is believed to be fairly reliable . Because of the scarcity of mine elevation data , all available information sources sometimes had to be utilized to make a rea- i sonable estimation of depth of cover . Where information was sufficient and where different methods of determining overburden were available, an effort was made to cross-check the overburden determination by testing one method against another . For ex- ample , ' elevations taken from mine maps were checked against data T from nearby drill holes . ' Incongruities between overburden determinations of differ-. ent mined areas on this map are attributable to four variables . First, topography above different mined areas varies over the coalfield. Because overburden thickness in areas of nearly hori - zontal beds is largely a function of topography , it can be ex- pected that the depth of cover will vary with the topography s k V-5 1 I' throughout the area. Second, there is a considerable variation { in the stratigraphic interval between the various coal seams throughout the coalfield . Third , faults disrupt the continuity of strata in the coalfield, and the resulting offset of coal I j seams has produced differences in overburden thickness in adja- cent mined areas . Finally, there is a slight amount of dip to the south and east throughout the study area . Coalbeds become progressively deeper, and overburden increases in thickness , in these directions . Mine-Pillars Map The purpose of the mine-pillars map is to delineate within each mine , and mine level , the areas where pillars of coal have been removed ( "pulled" or "mined-out" ) and the areas where pil - lars were left standing . It is important to realize that pillars which are shown in place on the most recent mine maps may have deteriorated , and possibly collapsed , since the maps were made. The reliability of the map showing areas where pillars have been pulled is commensurate with the .accuracy and completeness of the original mine maps . Individual coal mine maps with a scale of 1 "=200 ' ( 1 : 2400) were reviewed to determine the areas of pillar extraction and the areas of remaining pillars . The areas of pillar extraction and pillar non-extraction shown on the individual mine maps were visually reduced to a scale of 1 "=2000 ' (1 : 24000) and were compiled to a copy of the extent-of-mining map. k 01.r..:61 9 V-6 .,.,... A _1 r: It became apparent during the compilation of the mine-pil - - tars map that many of the individual mine maps were of dubious accuracy and are considered unreliable as far as delineating areas where pillars were pulled. Often, the individual mine maps merely indicated that large areas are "worked-out," but did not show •the outlines of pillars which were left standing and z . pillars which were pulled . On such maps, it is impossible to ' tell how many pillars , if any, remain in these "worked-out" ? 3 i ;-areas:.. R.. -- In - fact; miners report that an average of 30% of the orig- - inally available coal must be left in a mine , even under the best of conditions . Usually , the percentage of coal remaining is much higher, and commonly 40% to 50% of the coal originally in place is left behind. This residual coal is left in the backs of mines as a means of roof support , in mine floors , and in pillars . Some pillars are purposely left to protect main haulageways and shaft areas ; others are left in order to maintain a margin of safety while nearby areas are worked. If it is as- sumed that 30% of the coal originally in place was left behind when a given area was "mined-out;' it is probable that some pil - lars still exist in that area even though active mining ceased years ago . The presence or absence of standing pillars underground is critical to the question of mine subsidence potential . If near- ly all pillar support has been removed beneath an area , it is r 51 • likely that subsidence over that area occurred shortly after the cessation of mining and is now essentially complete. How- ever, in those areas where pillars are still standing it is likely that subsidence is not complete. Eventually the pillars - in these latter areas will collapse due to the separate or com- bined effects of air slaking, ground water, stress build-up from other parts of the mine, and increased surface loading from newly constructed buildings . Therefore , areas shown on the mine-pillars map as having remaining pillars should be regarded as potentially t more hazardous than those areas which are shown as having most I( of the pillars removed . .I Probable-Thickness-of-Extracted-Coal Map The purpose of the probable-thickness-of-extracted-coal map is to determine the maximum possible height of the void space -- which could exist as a result of mining activities . The height of the void space is assumed to be equal to the thickness of the coal extracted in a given area. This thickness would then be equivalent to the maximum amount of surface subsidence which could occur over that area. 4= r ,. It should be :Ilhei:ktneas:'olfnc::rilYina:ehse'mliinnei:gooPfr:cotice ewas toleavea certain provide support for the mine opening. Where this practice was I_ followed, the full height of the coal ' was not removed. Since no records were kept of the amount and distribution of roof coal T _; V-8 r left in the various mines , it was decided to ignore this possible discrepancy and to assume that in all cases the thickness of the coal extracted equalled the total thickness of the coal in place . In compiling the probable-thickness-of-extracted-coal map , the following procedure was adopted. First, coalbed thickness data were accumulated from 1 ) mine maps and mine history reports of the Colorado Division of Mines; 2) drill -hole records of the Rocky, Mountain Fuel Co. ; 3) coalbed isopachous (equal thickness ) maps made by F. D. Spencer and included in Lowrie ' s report ( 1966 ) ; and 4) information obtained in interviews with local coal miners . Spencer ' s isopachous maps cover the area north of Baseline Road (40° N . latitude ) and supplied most of the information used in ' making the probable-thickness-of-extracted-coal map in that area . The other three sources provided the data which was used for the area south of Baseline Road . The thickness information was plot- - ted on ' the extent-of-mining map and was contoured using a five,- foot interval . The values used in contouring areas underlain by multiple-level mining were obtained by summing the void spaces i x `"' heights of the individual levels . i It should be noted that the estimated void space in certain mined areas , such as the Nonpariel -Centennial (Old) mine complex and the Black Diamond No. 2, is based on widely spaced data points . As a result of this scarcity of data , the map may not represent the actual variations in coalbed thickness within % z 'thes'e mined areas . V-9 In spite of the above problems , the map is considered re- liable within certain probable minimum and maximum void-space heights . The heights of mine openings were seldom less than five feet because of economics and the limitations of machine mining (after 1946) . Since there are few areas where coalbeds attain a thickness of more than 15 feet, it can be assumed that mine openings are usually less than that figure . The map shows that most of the maximum possible subsidence falls within the li 5 to 10 foot range , and that the areas of maximum possible sub- sidence greater than 15 feet occur mainly over those localities where there was multiple-level mining. Subsidence-Inventory Map The subsidence-inventory map is the result of a program composed of field observations and interviews with local resi - dents . The purpose of this program was to locate the known subsidence areas in the Boulder-Weld coalfield . Areas of pre- sently ( 1974 ) observable subsidence and areas of reported, but no longer observable , subsidence were noted. Also, observations were made in areas where there is some question as to whether the area was even undermined. A number of criteria were used to determine where subsi - dence had occurred. In the field, pits and collapse features ' I over areas of known shallow mining were considered positive identification features of subsidence (Figures 7-14) . ,. Closed ;I I a • z t 41�• •1.14.---4 -E• • • � � �I. � C • fi, r . Figure 7. Collapse over room of Marshall No. 1 mine . The collapse area is approximately 15 feet by 30 feet and is about three feet deep . From five to ten feet of coal were _ extracted from this area at a depth of about 50 feet. Lower slopes of hill in background are also shown in Figures 6 (Area A) , 8, 31 , and 32 . Locality 4, subsidence-inventory map . F' • S %.rte 0 '1 'Y'M`Y y. i r rA i'i j g i imrw } ^i Figure 8 . Collapse area over Lewis No . 1 and No. 2 mines . Rooms of these mines are expressed by depressions and pillars by ridges. Mining was at a depth of less than 100 feet, and five to ten feet of coal was extracted . Compare joints in exposed sandstone in foreground with same area shown on Fig- ures 31 and 32 . Locality 7 , subsidence-inventory map , c? it61t X1/4O OA AS%6CieSAM }i a+ 2 i.1F.gy ! klf 7 .0. • Figure 9 . Collapse over room of Lewis No. 1 mine . Pit is about ten feet by 15 feet and is three feet deep . From five to ten feet of coal was extracted at a depth of approxi - mately 50 feet. Flume carrying irrigation water in middle 4[ background must be periodically re-set because underground mine fires in this area are causing continued subsidence . Locality 7, subsidence-inventory map . 3 f i'� ��•j N T mar '' y �'S!' :'y � 'wYF - _ t^,r N ! wI y rw • wy .. f t a'* ya°� 4 b.₹+c t�yt : M "- "gam a.�t � 6' Figure 10. Recent subsidence over Lewis No. 1 and No . 2 mines 1 brought on by underground fire . Note three puffs of grayish- white smoke . Mine is less than 50 feet deep and is above water table . Collapse and fracturing of overlying beds permits circulation of air for continued combustion . Between localities 7 and 8, subsidence-inventory map . i a i *-- ,rte�,..,.»,�-•.. . ..,,�,,. i k" c1 _ =Y �.. s �.. . . ar Figure 11 . Large subsidence nit over the Premier mine . The pit is approximately 30 feet in diameter and eight feet deep . Five to ten feet of coal was mined at a depth of about 100 feet. Near locality 1 , subsidence-inventory map . • a Y , -z �.• .. r sx ` - Yeti tot Clintea"(te.C45\4715141.110), J r ' �_ h turf: Y., + 'T. -,,,,y M •! . '`I I mow' ta�Y�yS t"�t ^~ . 9 y /.i _ [•h' _ Figure. 12 . Large , well -developed subsidence pits over rooms of the Shanahan mine . Pits are eight to ten feet deep and are 15 to 25 feet across . The coal seam at this mine was un- usually thick ( 10 to 15 feet) , which accounts for the large amount of vertical subsidence . The mining depth was less than 50 feet. Locality 21 , subsidence-inventory map . 0a `�r R� yti y i ter, t v ..ys ♦ a:.n'y 1. ✓r "1"isill .4� a-Y[ tom. 4- :` - •,! '.'.... '"+"+Mik:,,. % p a • a., '-...'- •T .J -4.'".,,;._ .awe=-a :a !,'sr"i" c �? 'x. n 9 aal vv +� c 3i,, : . 4, • i' Figure 13. Collapse pit over the Allen Bond mine. Features such as this aided in locating the true position of the Allen Bond mine . The previously reported position of the mine showed no evidence of surface subsidence . A thick ( 10 to 15 I feet) coal seam was mined here at a depth of approximately 50 feet. Locality 19 , subsidence-inventory map . k. • P , . _G r � .. ,t. -.t-----v. -�. :t....e,• I t +M.�"_ ��. x..'' r �yz • 1' 1+LT.— L a.�- . 'e"r a 'Y[₹1^ -w+.t-a..[ -oy,,,. 'e �'tgtt.-4t�"� d`, ”: `.'..��. vim- A v... 'cc way �-4--,'. N- Figure 14. Numerous subsidence pits above an unreported mine just east of Erie . No maps were found of this mine in the files of either the Colorado Division of Mines or the U. S . f. Bureau of Mines . Examples such as this illustrate the neces - r sity for field reconnaissance of all prospective development areas . Based on conditions in nearby mines , it is estimated that five to ten feet of coal was extracted at depths or Q e' to 100 feet. Locality 67 , subsidence-inventory map . tr 1 • Y.l depressions (Figure 15 ) , features of less positive subsidence evidence (swales and broad ground "sags , " Figures 16-17) and areas of reported but unverified subsidence were also noted . Recent (1969) aerial photographs were of some use in delineating areas of subsidence over areas of shallow mining such as the Fox, Allen Bond, Pluto, Northwestern , and an unknown mine in NE 1 /4, sec . 18, T. 1N . , R. 68W. In Weld County, older (1949) aerial photographs were used to determine an area of subsidence over the Shamrock mine (depth of cover about 100 feet) . This area was leveled and reclaimed for farming in 1956 and all surface evidence of subsidence was obliterated at that time . Interviews with local residents were valuable in pinpointing areas where subsidence and related structural damage had occurred in the past. Interviews with miners were especially useful in determining where subsidence had occurred because these men were aware at the time that a given area was being undermined, and were watchful for surface effects . Field observations of struc- tural damage to buildings , streets and sidewalks ( Figures 20-24) were also used to determine subsidence occurrence. Numerous complicating factors were encountered in the iden- tification of subsidence features . In addition to the land- leveling program conducted by the U. S . Department of Agriculture • over the Shamrock and other mines , individual farmers sometimes restored land damaged by subsidence . Shafts and pits were filled • with debris and were then covered with topsoil . Subsidence evidence • also is masked by crops and tillage . This is probably the case el Aric51 ,9 V-11 4 i =44.. I ». +t. AL ' await 1 ?,.wy Y { V. 1 _ V Ate • _ ' • �_Y�t+�-fn's,.F`yl 'v+��2f� �q�taS� YYYYYY��TTT t Pfd R ^�v y,,.-�- w �yjA.. a :,1 ' ,�y:�re* .`tom 1 3 �^ q _ j Figure 15 . Water-filled depression over Nonpariel mine . De- pression is partially closed by base of section line road . This is a typical example of a questionable subsidence feature . ' s Near locality 40, subsidence-inventory map . *' fr r Y g c,;44 ,Y A � • 3 Figure 16 . Broad swale over Lincoln mine . The swale in mid- dle foreground is fortuitously outlined by shadows cast by setting sun . Normally, this feature would be hard to discern by the unaided eye since it is quite broad ( 100 feet) and is only two or three feet deep . The mining depth at this locality is 150 to 200 feet and five to ten feet of coal has been ex- tracted . Tipple of the Lincoln mine is in background . Locality 77 , subsidence-inventory map . cal #.51.-14‘) 2 cS f-s s x SM� S 4 t � 1 J.:1'e- 44 t s 4, . tsy - t" t^ WM .�+f S. .y. bA.+'.�.+h+✓•.M9-Y� '3 Y 7 iNr'. '�+,vY•*12 S. S t ` xiy red 'F- c xn 1r , • �' .•i • • Figure 17. Broad sag over Morrison mine . Depression has a ' relief of only a few feet and does not really provide defini - tive evidence of subsidence . Careful survey measurements might show that the depression is closed , and this would strengthen the case for a subsidence origin . Five to ten feet of coal were extracted at depths ranging from 100 to 150 feet. Near locality 69 , subsidence-inventory map . • • 1 44 • L Figure 18. Water-filled depression just east of Russell mine . This depression lies a few hundred feet beyond the reported eastern limit of the Russell mine . This may be a case of sub- sidence over an area which was poached and the mining was not reported. The shallow ( one to two feet) depression may also 4 be the result of wind erosion . Locality 94 , subsidence- inventory map . 1, }-,-, 4 t `1't rri k A /yq� ��? y y,lift t ‘.. i III( Ty .~ rr .,-,} Y TA-Jerr 4gTt- f a� .„0.y; .-6a rtz- rr. wt r '.,r„ -r "it G 'A:* r .. .are, r ��{� .'.1"...**:-*wI `. 4 _.N aru,. i ........11,?*' a*t >o-0...y. �, 'Crt"" 1 -_ mtl' �Y Figure 19. Sand dune area one-half mile west of Firestone. Undulations of fence line indicate the irregular nature of the topography. This area overlies the Frederick mine where a five to ten foot coal seam was mined at a depth of 100 to 150 I feet. The poor , sandy soil of the area and the close proximity of an undoubted dune field indicate that the irregular topog- raphy is due to wind deposition rather than subsidence . t Y Y�F . ., -i t- ,�, 7 s, '. } a� i �1 , '/ : YEA ` --*—«�, ,�.( r - A' . ---eC 4_ rt ,. 4. ^ _ Id 4 '''.1' µ-4� ft ... +FYI' ,fa t ,y t ^YI 4{ Figure 20. Subsidence over Strathmore mine , South Longmont Street, Lafayette . The low sag in the front lawn and the front walk are subsidence related . This " subsidence" is ac- tually the result of compaction of trash and rubble used to fill a true subsidence pit which formed in 1956 (Denver Post, May 27 , 1956 ) . There was rapid collapse and overnight develop- ment of a hole 40 feet deep and 15 to 20 feet square . Locality 55 , subsidence-inventory map . el f:,e"-441 ,„ t a 1 i - tt• c • :4 yJ TX?-34;-% F •y, f 3 1- ro,.T 'f„! M y-'• }ate y .".T Y } K � sY �a MY Y a. m° w 1 } �� ,s. . + +"9'c. j.‘"‘ '. •,sar.`: r .rtq-#.+.,'tip. SY.*Z s,rv2 ••• h ' '.v Figure 21 . Subsidence over Strathmore mine , South Longmont Street , Lafayette . The most recent damage to the street has not yet been fully repaired . Mote unpaved section of street and sagging side - walk. The coal seam in this area of the Strathmore mine was quite thick , and the probable thickness of coal extracted was 20 to 25 feet. Depth of mining was 100 r� k:so to 125 feet. Locality 55 sub- • „� t sidence-inventory map . f}e `Z Lor:Ityrn ' �7 v. sisa g.. f 1 , ) ,,, �* :' Figure 22 . Front stoop of house a, to the right in Figure 21 . This I '' f s, .. house is immediately south of t1 home shown in Figure 20. The i • xi walk has pulled away from the r ,', stoop and it in turn has pulled fi away from the house . Bricks , have been jammed beneath the r house and beneath the stoop for , ice temporary support. Locality 55 , subsidence-inventory map . 1._� , ✓'g�ibpg.r gam,-[ eel 'qc-11 - f � I - "s , , as Tr" z at;-- — L: i { £ , . re b4*?y i+.•4e. *.�4' }" :C� - .h fi"`..v � k '.. a'6 r. ` �� `t:;`' .44 a :_ , �'#'` ' TM Ytat .1'4`�- � '�': Figure 23 . Subsidence pit at a trailer court in Lafayette . Ground began caving in the early morning of August 29 , 1974, and continued to enlarge until noon . Final dimensions of the subsidence pit were 24 X 18 X 15 feet. The subsidence occurred in a vacant area and only minor damage to utility lines was sustained . Had one of the large "mobile" homes shown in the background of this figure been parked on top of the subsidence area it is doubtful that it I ` could have been moved quickly enough to save it. This recent event is a dramatic example of continuing subsidence problems in an area where mining ceased . over half a century ago. s i f ' t `{ s U . 1 (r ;{ .f 1 ' f }any2,1/440,9 • � L' 1 r� .F y_ y °}" F a ` f r ,—u 4S .. a f s i F Figure 24 . Detail of subsidence g pit at trailer court { in Lafayette . The upper 12 feet of the subsidence pit walls are composed of sand and silt size material ; the lower three feet of the pit consists of bedded , angular gravel . The subsidence occurred over the Strathmore mine which lies at a depth of 100 to 150 feet and was last worked in 1919 . Normally only one level was worked in this mine but in the area of the trailer court two levels were mined and it is esti - mated that a total void space of 20 to 25 feet was - created . k t , ; (, 1 am;, ' .. 'd �M1'• Y../tz .� a�i:� icy:.' I1 Figure 25. Garage over Black Diamond mine . At this locality, five to ten feet of coal were extracted at a depth of 150 to 200 feet . The garage and house are fairly isolated , so that the surrounding terrain is relatively undisturbed by man . No pits , swales , or other indications of subsidence were found in the fields around the house . For this reason , the damage to the garage is thought to be due to swelling soils . Note bow in roof line along gutter. Locality 15 , subsidence-inventory map . .p . . soa, n ti-79" `0®8(li tar'.!Ara Wis Sawa Si r•N' ..s" ^�� .,wx LCD a 'liR + a. . tl6n6f�C�y��,�� Lq . _tiyy{3gJ�P .:'Y - IS3Jls�ly?imp). ,._ .� i VLF . w- ®YiV>➢LIYIM! x rmi S rentTa+'7a:..le!i63 'h�!ew.�M� v'V ITTJ pP)a(+5�9%L 9p•.�.fine foci , 11t •.i*.6Tf. 'w'.&L QSit..�lt A,.2?1�i6f Q.$J i?Lt& u.m lRN'�IiISOIRCIPP 0 rw t�U "'r W% �Y+,5 P 1 YJ2d1 iNG aRII !^/A{♦pcC!'�.r •w`:f r� ifits RnY^'C'x.�➢ii'!k" 7.-vs <rw'°n„^sL C3s- - �ZP K'+�t^e•��{ �"��i � ..Cyn y,� CtirY+..wj+.'a'ww�wYn 9e+nX, ; Koh.. �F �jr ��it.b ss�,��+ � '"fir- �� . s '�x'� Figure 26. Detail of garage shown in Figure 24. Stairstep cracks ` in brickwork are one-half inch wide . Window has rhomboid shape , and glass is cracked . This damage is similar to what one might expect if ground beneath foundation had subsided . Locality 15 , subsidence-inventory map. g PC' _ 31.. 9 C E, y{: .4 Mj , Y� . ; Figure 27 . Damage to VFW hall , �:, wr ' Main Street , Louisville . This f - 4•� - ,3141 '.„ part •of Louisville was under- -A I , y � , Gam '" 4 mined many years ago . A seam �. -1 .�� ). eil ;1 . a Th 10 to 15 feet was extracted at • ; �� s „` ., ' � a depth of about 100 feet . Be- � � � ., n six „ �.Aa� ;�' k cause the mining occurred so ,r}"�' �f��; ` , °"ft4 long ago , it is thought that 4. 1r'. p�- , �a;y� �: the damage to this relatively t •I' t az t- -Ac "4 ; recent building is related to 4'i , 11 ' faulty design or construction , r '...4 1, *tr, w rather than to subsidence . r � ''''—' +�",�b 1 '4-�.� � Locality 43, subsidence- 4 G7 ,a ,pp 144 Y � � . � inventory map . r r�" 4 .yy �_ 1 fI . i 4:49% i j YG y t wt Y µy[ ' 2 s - , r _ Figure 28. Abandoned building, Main Street, Louisville . The un- dulatory line of the siding and the rhomboid shape of the windows s suggest torsional effects which might be associated with subsi - dence . However , the obvious age of the building suggests that the structural warping is simply due to general deterioration over a long span of time . Locality 43 , subsidence- inventor rRa , -I ,_.. ;_ i RA_ in a great many areas of the coalfield, notably over the New Crown , Matchless , Helca , Rex #1 , Mitchell , Morrison , Frederick , Puritan , Grant, and Witherbee-Peerless mines . Another complicating factor in subsidence identification is that surface effects above deeper mines (greater than 200 feet) are likely to be faint. Unless observed immediately after mining, they may soon be totally obscured. Subsidence over deeper mines is not represented by well -defined pits and swales , but is typified by broad depressions several hundred yards in diameter . Even broad depressions over known mined areas may be suspect because "blowouts" (wind-eroded depressions) occur in the area, especially around Frederick and Firestone (Figures a 18-19) . f Damage to structures built over mined areas cannot always i be attributed to surface effects of caving in the mines . Other factors which must be considered before ascribing damage to subsidence are 1 ) instability of the slope on which the struc- ture is built, 2) compaction of fill , 3) swelling clays around foundations (Figures 25-26) , 4) thermal effects , 5 ) faulty de- sign or construction (Figure 27) , and 6) gradual structural deterioration with time (Figure 28) . Furthermore , minor struc- tural damage to highways , railroads , and irrigation systems , as a result of subsidence , is usually repaired on a routine basis . Lastly, subsidence damage to residences may be repaired or dis- guised so that property values will not be lowered . Si_` 61 V-12 4 Y Reports by residents and miners are useful in locating 4 past evidence of subsidence, but are often difficult to verify . In one such instance , . a miner pointed out that he had assisted z in surveying a grid of points over the Eagle mine SW 1/4, sec . 14, T. 1N . , R.68W. , where the depth to mine workings is approxi - mately 300 feet. A subsidence of 23 inches was measured three to six months after pillar removal . The area is presently being farmed, appears to be a smooth slope , and no distinct subsidence , evidence is discernible. After taking the above complications into consideration , it is estimated that 90% of the subsidence which can be presently observed has been identified. The subsidence inventory has shown that no well -defined, presently observable subsidence occurs in areas where overburden is greater than 150 feet. Sub- sidence in areas with a greater depth of overburden is difficult to verify by routine field observation . '"F F 4,' F { i z 4 V-13 i VI . FIELD _W0RK __ Field work consisted of personal interviews , foot traverses over mined areas , and examination of local historical records . i Approximately 15 man-days were spent in interviews with persons having knowledge of past mining and subsidence in the area . Such people included active and retired miners , local librarians , his - torians , newspaper editors , city and county planners , and .land- owners with property overlying mines . Initial contacts were made through letters of introduction provided by the Colorado Geologi - cal Survey and through advertisements placed in local newspapers . k As the interview program progressed, word-of-mouth suggestions I led to meetings with additional knowledgeable people . A list of the individuals contacted is included as Appendix A of this Ireport . Retired miners were most helpful in providing information 1 1 on mining practices and subsidence over the more recent mines i in Weld County. In Boulder County, many local residents gave 1 descriptions of past subsidence events and pointed out present- day subsidence features . All subsidence reports stemming from these interviews were then field checked . Approximately 25 man-days were spent in field checking the above reports and investigating other areas of possible subsi - dence . The land above the coal mines was traversed to observe evidence of subsidence and unrecorded mining activities . Every A s5, A2 ai aC,. mined area in the coalfield was walked and (or) driven over , or was , at least, observed from the nearest section line road . Aerial photographs were carried in the field, and the lo- cations of possible subsidence features were plotted on them. Observations were summarized in field notes written at each lo- cation visited. The results of the field survey were utilized in the construction of the subsidence-inventory map. In a few cases , field observations indicated that mine boundaries on the extent-of-mining map had to be enlarged or reduced . Historical records dealing with coal mining and mine sub- sidence were examined in the town libraries of Louisville and Lafayette and in the homes of long-time residents of the area . The State Historical Society library, the Denver Public Library, and the Denver Post library provided access to back issues of local and regional newspapers now long defunct. With few ex- ceptions , the newspapers and records examined dealt with mine collapse only as it affected the miners or the mine workings . Instances of surface subsidence during the time of greatest mining activity ( 1905-1945) usually occurred in sparsely in- habited areas where land values were low and were either not newsworthy events or went unnoticed . y s VI-2 I VII . SPECIAL-PURPOSE ACTIVITIES In addition to the main programs of basic—data map com- pilation , field work , and interviews , certain other activities relating to mine subsidence detection were carried out. These activities consisted of a photogeologic review of recent (1969) aerial photography, a comparative study of this photography with .i aerial photos taken 20 years earlier, and a study of special , low- sun-angle , low-altitude aerial photos taken over selected mine I areas . Acquisition and study of multi -band photography was ini - tially considered , but it was later decided that the low-sun-angle I photography offered a more fruitful line of research. Photogeologic Review A photogeologic review of the coalfield was made using Agri - cultural Stabilization and Conservation Service (A.S..C.S. ) photos i taken in 1969 at a scale of approximately 1 "=1667 '- ( 1 :20000) . r Stereoscopic examination of the photos showed that soil and vege- tation cover obscured nearly all the bedrock geology. Only two rock units occur within the area, and neither have any distinc- tive photogeologic characteristics . More disappointing is the fact that few of the many northeastward-trending faults which have been reported in the area can be detected on the photos . ' It has been equally difficult to find field evidence for these A� - i ;) VII-1 v�_IrS� �� • A+~ ):k, ?,' 1t: faults . As noted above, most of the faults are based on sub- surface data , and their lack of recognition in the field and on the photos is probably due to a combination of low dip , soil and vegetative cover, and similarities in lithology between the two surface rock units . The air photos were useful in making a rapid appraisal of the surface overlying mined areas . The surface could be clas- • sified as showing 1 ) well-defined subsidence features , 2) pos- sible indications of subsidence , and 3) no evidence of subsidence . Well -defined subsidence features usually take the form of small pits 10 to 30 feet across and 3 to 10 feet deep ( Figures 7-14) . Rarely, there are larger areas of collapse forming depressions x 150 to 100 feet across and 5 to 10 feet deep . At a scale of 1 "= 1667' (1 :20000) , the pits appear quite small on the photos and single , isolated pits are easily overlooked (Figure 6) . For- tunately, they commonly occur in easily recognizable clusters;,of a half dozen to a hundred or more pits . In untilled pastureland, the pits have remained undisturbed since their formation and are easily recognized on the photos . Where the land has been tilled , the pits have lost their definition , either because the ground has been worked over many times during the normal course of farm- ing, or because an active program of pit-filling and land-leveling has been carried out by the landowner. • Possible subsidence indicators include slight depressions , areas of mottled crop cover, and areas of poor drainage . The �1 1 . VII-2 P I mottled vegetation patterns are produced by areas of darker- toned lush vegetation whose vigor is due to a more abundant supply of water collecting in subsidence-formed depressions { !' (Figure 15) . If too much water collects , however, the vegeta- tion is j killed and the depression is marked by a small pond or ` by a mud flat ( Figure 18) . The latter sometimes have alkali crusts whose white color is distinctive on the photos . Mottled vegetation , shallow depressions , and poor drainage are not de- finitive subsidence features . All can be produced by natural processes other than subsidence, such as wind (deflation) , or 1 by the activities of man , such as the construction of stock ponds and the opening of borrow pits . The photogeologic review showed that in the coalfield well - defined subsidence features are usually present in those areas where depth of mining is less than 100 feet . Where mining depths are 100 to 200 feet, good subsidence indicators are sparse , and one must work with less definitive features such as swales , shal- low depressions , and areas of poor drainage . In those areas tt where mining has been at depths greater than 200 feet, the sur- t face usually has no subsidence features which can be observed on ?; the photos . i , As a rule , the correlation between mining depth and photo rec- I ognition of subsidence features was also found to apply to field observations . Even though subsidence has undoubtedly occurred + in areas where mines lie more than 200 feet below the surface, i I 9 VII-3 A the effects of such subsidence are probably spread over a wide area. It is possible that these subtle subsidence effects might be detected in the field by comparing precise surveying measurements made before and after mining. Comparison of 1949 and 1969 Aerial Photography - A set of aerial photos taken in 1949 by the U. S . Geological Survey at a scale of 1 "=1385 ' (1 : 16620 ) was examined and compared with the A.S .C . S . photography taken in . 1969. As to be expected, the larger scale of the earlier photos made recognition of subsidence features somewhat easier . Moreover, the older photography in one case (Shamrock mine) showed subsidence pits which were not visible on the more recent photo coverage . Further investigation showed that between the two dates of photography an extensive program of pit-filling and land-leveling was carried out by local ranch- ers in cooperation with the Soil Conservation Service (U.S .D .A . ) . The older photos prove that, in at least one area, subsidence did occur even though present-day surface evidence of subsidence is lacking. , - A photo comparison was also made of areas where new coal mining had taken place during the time spanned by the two dates of photography . The later photography did not show any subsi - dence features over the newly undermined areas . The lack of subsidence evidence in these areas leads to two very different -`-a i_fi6.3 VII-4 conclusions . The first, and most obvious , is that no subsidence occurred over the areas mined between 1949 and 1969 . The second conclusion is that subsidence has occurred, but that its effects on the surface are subtle and diffuse. The fact that the areas mined during the period 1949-1969 generally had an overburden thickness of more than 200 feet lends support to the second possibility . Low-Sun-Angle Photography - Through the cooperation of the U. S . Geological Survey, k 9 y, a number of large scale , low-sun-angle aerial e photographs of selected areas in the coalfield were obtained. The photos were taken on July 23 , 1974 during the early morning ( 7:00-8: 30 AM) , while the sun was still low on the horizon . The 1 low angle of the sun caused ground features of low relief to cast long shadows , and it was hoped that these shadows would en- hance the outlines of the shallow depressions , pits , and swales which so frequently indicate subsidence . u The areas selected for low-sun-angle photography included i { a control area of well-known and well-defined subsidence and a r`, < half dozen areas where there was doubtful evidence of surface subsidence . The photos used for study have a scale of a "pproxi - mately 1 "=450 ' ( 1 : 5450) and were made by enlarging 2. 25" X 2. 25 " negatives . Enhancement is most apparent in the control area at t: j Marshall and can be seen by comparing Figures 29 and 31 with Figures 30 and 32. The former were made from a photo taken ,y 3 01_.1 s� J z Y• x2 4pill,' i ' '� , L., ✓ � . sL fi -< 1 M ( \61, Jpp .I (p�y�y^g`pIi�l`"�.wy, t Y _e • y� , , �. .,t 'ice.71. ,-,..,- �L 'c°fT r: � dr1�y '#'.p �°t+"*s s :. F°q`_ �. i raj y " .. S ? fM I eb b - s `c, rte. • � w w: ' 4.a. �.� ,t `y e, s V b r it 1 S e w .. ;t '. n . C rY44 y -T, , 11T f , u�t'1= . S �4 . V! 'WY b,,, r-16 kit *Y i.....'�• .,, Figure 29 . A. S . C . S . photo of Figure 30 . U. S . G. S , photo of area A , south of Marshall area A , south of Marshall High-sun-angle Photo Low-sun-angle Photo The shadows on the low-sun-angle photo enhance the outline of col - lapsed rooms at a and b . The same features ( a ' , b ' ) are nearly indiscernible on the high-sun-angle photo . The subsidence pits at c ( c ' ) are also more strongly enhanced on the low-sun-angle photo . The two figures are both enlargements and have an approximate scale of 1 "=450 ' (1 : 5450 ) . The enhancement of detail brought about by enlargement is seen by comparing Figures 6 and 29 , both of which were made from the same negative . f. V '. � f.. n. �le4 4714:‘'' r '6 ' e. . 't a'. "iii •�. t .t.' " .f, .n, 2,4'7 ' :.af a-.. r. . iCj .1�� 'i _ S. w t x { • .a r 'i • �.� � •. - 1y.� A� ' ' � :yy• .� �� _ ti . E Ai, k c.�, a fi"r 3 gfa -.� Y 7 _ K'�i +• M'-• f P•' t Sy 1. -f.,. M1' 3{:.+ 1 :a..2,‘0,\,.,..: ;. 1 . t.� 44 J e;y, • 1, 1��).-' ak tl Ott' f •',. �. t� w r ! R * i %fr a i°�a k • 1 C 1.-- 1 �d �i �"yam ; h, .1 1 +1qq . ft 'i R , J Figure 31 . A . S . C. S . photo of Figure 32. U. S . G. S . photo of area B , north of Marshall area B , north of Marshall ' ! High-sun-angle Photo Low-sun-angle Photo 1 ,i Collapse features a (a ' ) outlining the rooms and pillars of the Lewis No . 1 and 2 mines are enhanced by the shadows of the low-sun- angle photo . The same features become blurred on the high-sun- angle photo because of the large amount of light reflected from the bare rock near mid-day . For the same reason, subsidence induced joints at b ( b ' ) are also better displayed on the low-sun-angle photo . Joints at b ( b ' ) are also shown in foreground of Figure 8 i and flume c ( c ' ) of irrigation ditch is in middle ground of Figure 9 . The figures above are enlargements and have an approximate scale of 1 "=450 ' ( 1 : 5450 ) . Figures 6 and 31 were made from the same negative . A comparison of the two shows the enhancement of detail brought about by enlargement. 01 =1r1a) f when the sun was high above the horizon ; the latter were made from a low-sun-angle photo. Subsidence pits , room and pillar outlines , and subsidence induced fractures are all better ex- pressed on the low-sun-angle photos than on the more conventional photos . The use of low-sun-angle photography to relieve the doubt surrounding "subsidence" features in other parts of the coalfield was less successful . Features which appeared doubtful when visited in the field ( Figure 17 ) still seemed doubtful when observed on the photos . This study has shown that aerial photographs have a number of applications , as well as some limitations , in mine subsidence investigations . Repetitive photo coverage can provide a histori - cal record of where subsidence has occurred in the past and , to some extent, when it occurred . It can also show where the ef- fects of subsidence have been masked by the later work of time and man . A major constraint on the use of aerial photographs as a means of determining past subsidence history is that the dates at which the various photo coverages were flown are not neces- „ sarily the dates of greatest mining activity . In areas of shallow (less than 100 feet) mining, subsidence features are strongly developed and can easily be recognized on air photos . Recognition is made easier by using low-sun-angle photography and by enlargement of the photos . The effect of enlargement is strikingly shown by comparing Figure46 with VII-6 of rtr c i i Figures 29 and 31 . The latter are merely enlargements of the I former, but the subsidence features which they show have been greatly enhanced by an increase in perceived depth and detail . It should be noted that there is a trade-off involved when one is choosing between large and small scale photos . Large scale photos show subsidence features very well , but require a large l number of photos to cover a given area . Fewer small scale photos are needed to cover the same area , but there is a greater :i likelihood of overlooking subsidence features . In areas of deep (more than 200 feet) mining, well-defined depressions and subsidence pits are lacking and subsidence as expressed at the surface is probably too subtle to detect by L ( normal photo interpretation methods . It is possible that such subtle subsidence might be identified by using sophisticated photogrammetric plotters in conjunction with large scale photo graphs taken before and after an area was undermined. Good plotters can measure very small differences in elevation, and [[ G changes of only a foot or two over newly mined areas could prob- ably be detected . The use of photos as a future historical record is limited by the costs of obtaining ground control , the costs of repetitive flying, and the costs of plotting machine time. • • t : • VII-7 ' elf ' h ti1d$4 AFs. VIII . LAND-USE PLANNING AND MINE SUBSIDENCE Background Mining activity in the Boulder-Weld coalfield started in the early 1860 ' s in the Marshall area and presently continues only in the Eagle mine. Although instances of subsidence had been recognized for many years , little thought was given to the relationship between underground mining, subsidence , and man- made structures on the surface . Towns in the coalfield were small , and rural housing was widely scattered. Subsidence could take place and go unnoticed , and damage to existing , relatively small structures could easily be repaired. Fields and roads could be regraded and kept in usable condition . These inconven- iences apparently were not of sufficient magnitude or intensity to cause widespread concern , and subsidence-related problems were accepted as a part of life and were dealt with as they oc- curred. The subsidence-hazard issue remained one of limited interest until recently, when accelerated population growth throughout the region produced significant increases in the density of residential development in—and adjacent—to undermined areas . Due to increased emphasis on land-use planning, and to ex- . panding development pressures , it has become apparent that a close look must be taken at areas of potential subsidence . The el SG1 9 VIII- 1 a If I i I increasing concern for the wise and safe development of land f is reflected in the passage of House Bill 1041 by the 1974 r I Colorado General Assembly . This law has brought subsidence problems (classified as a natural hazard) within the purview of the State , as well as the county and municipality. When considering land use in areas which have been under- F mined , the following questions must be addressed . 1 . Is or was there coal under the tract to be developed? 2. Has the full amount of subsidence occurred over worked-out areas , or can more subsidence be expected? 3. If more subsidence can be expected , when will it occur, and what will be its magnitude? 4. In an area in which subsidence is likely to occur, I`'r can remedial measures be taken so that the land fi can be developed safely? 5 . What are the legal problems likely to be associated with land development in— and adjacent—to areas of ' t potential subsidence? 6. Will advancing technology make it feasible to re- 1 enter old mines? This list of questions is not complete , but it illustrates the '1 complexity of the problem. 1 Since the Boulder-Weld coalfield is in the path of Front Range urbanization , it is timely that answers to the above ques- f 1 tions be found . Some of the questions are quite complex, and it 21(.:61..9 1 VIII-2 will not be economically practical to obtain answers for them. In such cases , the land in question may best be left as open space or greenbelt. When answers to land subsidence problems are not clear cut and definitive , the potential land developer should follow a program of investigation which , hopefully , will provide the data needed. The first step in such a program would be to study the maps which accompany this report , particularly the subsidence-hazard map. Certain areas , because of land ownership or because of proximity to previously developed areas , will be subject to con - siderable pressure for development . In these areas it will be necessary to undertake detailed, and relatively expensive studies to determine the extent to which viable and safe development is feasible . Subsidence-Hazard Map Purpose and Procedures - The purpose of the subsidence-hazard map is to designate , insofar as possible , those areas where ' development of the land surface may be affected by subsidence related to undermining . The most direct approach to the prepa- ration of a subsidence-hazard map would be to compare and con- trast information on the various mining factor maps with data on the subsidence-inventory map . Comparisons were made with this objective in mind to determine if any positive correlations S C.3 G1.9 9 VIII-3 { i I '� existed. It was hoped that such correlations would identify those factors which are most critical to the development of t j subsidence. I Instances of known subsidence were evaluated with respect to the following factors and combinations of factors : 1 1 . Presence or absence of pillars 2. Depth of cover `:I ''„ 3. Probable thickness of extracted coal ;:, 4. Dates of mine operation 5. Proximity to mapped faults {� 6 . Presence or absence of pillars plus probable . _ i'F P. _ thickness of extracted coal r 7 . Presence or absence 'of pillars plus proximity . to mapped faults 1 , 8. Depth of cover plus probable thickness of :4 extracted coal ;- 9. Depth of cover plus proximity to mapped faults It 10. Depth of cover plus presence or absence of pillars . C IA positive relationship was observed only between 'depth of ; cover and the presence or absence of pillars (No. 10) ' ` 1 . In the depth-of-cover range 0-100 feet , instances• `. of surface subsidence evidence occur just as often ; J over areas where pillars are absent as over areas • where pillars are present. 1 , VIII-4 j. 2. In the depth-of-cover range 100-200 feet, instances of surface subsidence evidence occur twice as often over areas where pillars are absent as over areas where pillars are present. 3. In the depth-of-cover range 200-300 feet, instances of surface subsidence evidence occur three times as often over areas where pillars are absent as over areas where pillars are present . 4 . In cases where the depth of cover is greater than 300 feet, instances of surface subsidence evidence occur twice as often over areas where pillars are absent as over areas where pillars are present. These observations indicate that, as depth of cover increases to 300 feet, the occurrences of subsidence evidence over areas where pillars are absent become increasingly more frequent rela- tive to those areas where pillars are present . Below 300 feet this trend is reversed , possibly due to the increased "bridging" effect provided by a thicker overlying rock section . It should be stressed that comparisons can be made only where evidence of subsidence exists . In areas where there is no Y surface evidence of subsidence , any conclusions drawn from the above 'observations should be used with great caution. This is particularly true with any attempts to relate the possibility of future subsidence to depth of cover and the presence or absence of mine pillars . or.,S1 9 VIII-5 1 I The almost total lack of correlation in the above compari - I sons (Nos . 1 -9) is probably due to the complexity of the rela- tionship which exists between room-and-pillar mines and surface ° ,I subsidence . In addition , the records kept throughout the years I of mining activity in the area are not sufficient for a thorough analysis of the relationship between subsidence and other mining factors . Another major problem is that the subsidence-inventory map shows only observed subsidence , and does not record. subsi - dence which may have gone unnoticed. It is possible that had a full and accurate record of subsidence been available, some correlations might have been established . 1 Basic Assumptions Used in Map Construction - The problems des- 5 ` cribed above indicate that no consistent rule can be adopted y` for predicting subsidence . The best approach appears to be one �� which is based upon the probable relative severity of potential Isubsidence in any given area . Since any undermined area may be affected by subsidence or post-subsidence settlement, all such I Iareas have been assigned a degree-of-hazard classification based on the following simple assumptions : :y 1 . Large undermined areas with no support ( ie . pillars removed) subside shortly (within months ) after support is removed . 2 . Caving proceeds upward from the mine roof, and by . I. the time subsidence effects have been transmitted if si ;.9. -_) VIII-6 k r xn to the surface it can be expected that no large voids remain beneath that particular area. 3. Occurrences of partial collapse (that is , cases Y where subsurface caving has occurred , but where the caving has not reached the surface ) were not t detected during this study. Therefore , it is assumed that, where surface subsidence has oc- curred, the subsidence is essentially complete. This does not include post-subsidence compaction and attendant surface settling . 4 . The inability to confidently predict the relative stability of a given undermined area requires a . conservative approach to hazard classification . Accordingly, it has been assumed that pillars left standing after mining ceased will undergo deterior- ation with time , and will eventually fail . The amount of time required for a pillar to completely deteriorate will depend on many factors , which vary in in in different areas of the coalfield . Eventually, all pillars will probably fail , and subsidence will probably occur over all voids in the study area. Hazard Classification System - Using the above assumptions , a classification system has been established to define the degree 21.0 19 VIII-7 of subsidence hazard in relative terms . This appears to be the most useful approach to the problem of the relationship be- tween land subsidence and land use . The categories of subsidence hazard are severe , moderate , and low. 1 . Severe - Areas labelled "severe" are those in which rapid and violent subsidence effects may endanger occupants of the area by causing the failure of building foundations , roadways , gas mains , and simi - lar man-made features . These areas are characterized by either 1 ) the presence of pillars (which are as- sumed to be undergoing decomposition ) plus physical evidence of void space , or by 2 ) the absence of evi - dence of surface subsidence . The collapse of decom- posed pillars could alter the complex stress and strain patterns in the overlying rock. This could initiate almost instantaneous local surface subsi - dence or displacement, thereby causing equally rapid destruction of structures in the area . The only ac- ceptable land use for these areas , without undertaking relatively expensive remedial measures , are agriculture or open space. 2 . Moderate - Areas subject to "moderate" subsidence are those in which the effect of subsidence might be suf- ficient to render man-made structures unsafe or VIII -8 � g361 unusable . The rate of subsidence would probably be slow enough to allow time for recognition of the problem, and if necessary, for the safe and orderly abandonment of the area. Possibly, there would be sufficient time for remedial action which could offset the effects of the subsidence. "Moderate" areas are characterized by the presence of subsi - dence features over undermined areas where pillars are reported to be present. This condition produces the potential for further subsidence and differential settlement . Appropriate land uses would include ag- riculture , open space , open storage areas , unoccupied warehouses , and similar uses which would require only a low population density. 3. Low - Areas of "low" hazard are those in which the rate and magnitude of any anticipated surface dis- placement would be small enough to warrant repair of affected existing structures . By using adequate engineering design , future structures in these areas could be built to withstand the anticipated stresses on their foundations . Below these areas , all or essentially all , pillars have been removed , and re- latively uniform and complete subsidence has already occurred. Problems in such areas would be reduced mainly to post-subsidence compaction and related tr:26 1.°_i VIII-9 surface settling . The only restrictions placed on land use would be the requirement that structures planned for these areas would be designed to with- stand any small movements which might be induced by post-subsidence compaction . Safety Factor - Factors such as angle of draw, attitude of bed- ding, and presence of zones of weakness due to faulting can extend the surface influence of a particular void well beyond the limits of the undermined area . Determination of the extent of subsidence at the surface is further complicated by the possi - �� bility of significant inaccuracies in the original mine maps . The effect of the inter-relationship of the above factors i is not amenable to quantification . It is therefore prudent to incorporate a "safety factor" into the determination of the ex- tent of surface area which might be affected by mining. This has been done by assuming a nominal angle of draw ( 35° ) . This angle was used in conjunction with the maximum mining depth (580 feet) recorded in the coalfield to calculate the width (400 feet) of a safety zone which extends beyond the mine bound- aries . This 400 foot wide safety zone is used throughout the - entire coalfield even though nearly all mines are less than 580 feet deep. The hazard classifications used for the zones of t safety are the same as those used for the adjacent areas which are directly over the mine. i l;' VIII-10 I �: I Where faults , or intersections of faults , lie only a short f distance beyond the 400 foot boundary, the zone of safety has been extended to those faults and intersections . Small modifi - cations in the width of the zone have also been made based on surface topographic control . Reclassification of Subsidence Hazard of Specific Areas - The hazard classification of all areas within the coalfield was based on the data available for this study. Reclassification of any part of these areas could be justified by the accumulation of more or better information . Such information might be de- rived from 1 ) more detailed maps than those available for this study, 2) field observations and measurements of additional sub- sidence not observed during this study, and 3) subsurface tech- niques such as core drilling and geophysical surveys . It is certain that the economic attractiveness of land development in the coalfield area will prompt investigations to re-define the subsidence hazard in- and adjacent- to specific properties . Planning Review of Subsidence Hazards of Specific Areas During the early stages of this study, it was hoped that a set of guidelines could be developed for use by those persons investigating the subsidence hazards of specific areas . It later became apparent that the complexity of the problems associ - 3 ated with subsidence was such that the most reasonable approach SitS S VIII-11 �4 to further investigations would be to acquire additional data similar to, but much more detailed than, that used in the prep- aration of this report. The preferred map scale on which to display the detailed data would be 1 "=200 ' (1 :2400) . For most areas , the development of large-scale maps showing basic data such as extent of mining , depth of cover, pillars , probable thickness of extracted coal , and subsidence occurrences will be only the first step in a land-use compatibility investi - gation . In some instances , the basic data will indicate that further investigations will be needed to demonstrate the via- bility of development. As in the case of hazard reclassification , such additional investigations will probably consist of subsur- face testing through core drilling and geophysical surveys . Subsurface investigations are expensive , and it should be expected that land development projects in the coalfield will be subject to some financial burdens not associated with projects of similar size in other areas . However , the area still appears to be attractive for development, and the more astute engineers , designers and planners will find ways to overcome the problems which exist. • 2 619 - VIII- 12 ZY Appendix A - Continued Local Residents - t. (Mrs . ) Amicarella , Librarian , Lafayette r Barlow, Niles, resident, Lafayette Bateman , Albert, owner of property above Electric Mine Coonts, Phyllis , resident, Marshall Dhieux, Vivian , City Councilwoman , Louisville Di Giacomo, Susie , owner of property above Paramount Mine Lewis , K. D. , homeowner near Shanahan Mine Ostdiek , Walter, Paclamar Farms , Louisville Reichert, A. E . , owner of property above Black Diamond Mine Rodelli , James , resident, Superior Sampson, Johana , resident, Marshall Waremburg, Clubert, owner of property above Acme Mine Zabler, ( Mrs . ) R. A. , resident, Lafayette Miscellaneous Boyle, Clyde , Charles Robinson and Associates Cochran , Dale , Charles Robinson and Associates Darnell , Clinton , Adolph Coors Co . , Engineer on Coors Pipeline (Mr . ) Ferryman , Burlington Northern and Colorado and Southern RR, Chief Engineer Gillen , Gary, Boulder Daily Camera McPhail , Donald, Univ . of Colorado, Professor 21.1.6 t Appendix A - Continued r' Miscellaneous (Cont. ) s Miller , Dean , Public Service Co. of Colo: , Supervisor , Transmission Engineering F 4' Rahmiamian , Victor , Colo. School of Mines , graduate 3 student t" Russell , William, Rocky Mtn . Energp Co. , Senior Engineer ; ! Sarchet, M. C . , Former Reservoir and Irrig. Co . , President h.{ Schreiner, Robert, Centaurus High School , Principal ` I Waneka , George , Waneka and Sons Drilling Co. $ Weimer, Robert, Colo. School of Mines , Professor i..; 1 , f 3 t ( r. 0 I I � i 7 1 ,C v 4 i ^�.1 •"S' 21 k y , y APPENDIX P, CITY , COUNTY , STATE AND FEDERAL OFFICIALS; MINERS; LOCAL RESIDENTS AND OTHERS INTERVIEWED DURING COAL MINE SUBSIDENCE STUDY City and County Governments Brouillette , Jason, Boulder Co . Planning Dept. , Head of Operations Heffington, William, Boulder Co. Eng. Dept. ' Pendleton , James , City of Boulder, Geologist Bedford, James , City of Lafayette, former Mayor Deppe , Daniel , City of Lafayette , Ass ' t. City Manager a . White , Daniel , City of Louisville , City Engineer Wurl , Leon , City of Louisville , City Administrator Lorenson , Burman , Weld Co. Planning Dept. , Planning Director Olsen , Gill , Weld Co . Engineer ' s Office Colorado State Government Deborski , Andrew E . , Colo. Div. of Mines, Chief Coal "- ` Mine Inspector " Platt, Thomas , Water Commissioner, Dist. 6 Gilmore, John , State Highway Dept. , Geologist, Denver Region Bower, Dwight, State Highway Dept. , Engineer, Dist . 4 Springer , John , State Highway Dept. , Maintenance Ass ' t. , Dist. 4 U. S . Government Dunrud, C . Richard , U. S . Geological Survey Colton , Roger B. , U. S . Geological Survey S.1,Ct S1 !i Appendix A - Continued I s .. U. S . Government (Cont. ) 4.144.0f ' Panek , Louis A. , U. S. Bureau of Mines Morgan , Thomas A . , U. S . Bureau of Mines I Darnell , Richard, U. S . Bureau of Mines Donner, Donald, U. S. Bureau of Mines Moreland , Donald , Soil Conservation Service, U. S. D.A. Active and Retired Miners s3 Astle , John , Lincoln Mine, General Manager ( Amicarella, Lawrence Clyncke , Marion Clyncke, Oliver De Novellis , Anthony De .Vi Scher,.- Andy Dhieux, August Ferguson , William, Lincoln Mine , former Mine Superintendent s . Gunther, Wilbur, Imperial Coal Co. , General Manager P` n Hawkins , Henry ht- Kolar, Frank, Eagle Mine , former Mine Superintendentts- t ` Miller, Manford ; a Reese , Charles , Eagle Mine, Mine Superintendents Sidle, Samuel Stolns , Edward, Lincoln Mine , Mine Superintendent Vaughn , Ambrose ;. T, u '� f- j1 9 X. SELECTED REFERENCES Averitt, P . , and Lopez, L. , 1972, Bibliography and index of '= U. S . Geological Survey publications relating to coal , 1882-1970: U .S . Geol . Survey Bull . 1377 , 173 p . Babcock , S . D . , 1973, Undermining as an element in land use planning [M.S . thesis ] : Edwardsville , Southern Illinois „ Univ . , 84 p. Brauner , G. , 1973, Subsidence due to underground mining ( In two parts ) 1 . Theory and practices in predicting surface deformation : U . S . Bur . Mines Inf. Circ . 8751 , 56 p . 1973, Subsidence due to underground mining ( In two parts ) 2 . Ground movements and mining damage : U. S . Bur. Mines Inf. Circ. 8572 , 53 p . Candeub, Fleissig and Associates , 1971 , Demonstration of a technique for limiting the subsidence of land over abandoned mines , N .T. I . S . , Tech . Rept. , P .B . 212708, 57 p . 1973, Demonstration of a technique for limiting the subsidence of land over abandoned mines , final report: L: City of Rock Springs , Wyo. , 28 p. Colorado Division of Mines , 1973, Coal 1973: Colo . Div . Mines Inspection Div. , 28 p . Colorado Springs Planning Department , 1967 , Mining report , Colorado Springs coalfield, a guide for future land use : Colorado Springs Planning Dept. , Geol . Sec. , 10 p . Colorado State, 1963 , Coal mining laws : State of Colorado, revised statutes , chap . 92 , pt . 1 , arts . 1-12, sec. 1 , 124 p . Colton , R . B . , and Lowrie , R. L. , 1973, Map showing mined areas of the Boulder-Weld coalfield , Colorado : U. S . Geol . Survey Misc . Field Studies Map MF-513. Dunrud , C . R. , and Barnes , B. K. , 1972, Engineering geologic map of the Geneva Mine area , Carbon and Emery Counties , Utah: U. S. Geol . Survey Misc . Geol . Inv . Map I-704. Flaschentrayer, H . , 1958, Considerations on ground movement phenomena : Colliery Eng . , v. 35 , no. 8, p . 342-350 and no . 9, p . 391 -398 . o 4,Ili 1 l Gillen , G . , 1974, When coal was king : Focus Magazine in I_ Boulder Daily Camera , March 24, 1974, p . 3-6. Grosvenor , N. E. , 1964, Coal mines of Colorado, Adams County 'Vi (map) : Colorado Sch. of Mines Found. , Golden , Colo . ,f 1964, Coal mines of Colorado, Boulder County (map) : ` Colorado Sch. of Mines Found . , Golden , Colo. 4; ^{ '' 1964 , Coal mines of Colorado, Weld County (2 maps) : I 3 Colorado Sch. of Mines Found . , Golden , Colo. a Herbert, C. A. , and Rutledge , J . J . , 1927, Subsidence due to I coal mining in Illinois : U.S . Bur . Mines Bull . 238, 59 p . o '; Holt, R. D. , 1972, Bibliography, coal resources in Colorado: #, Colorado Geol . Survey Bull . 34-A, 32 p. i ,y Hornbaker, A. L. , and Holt, R . D. , 1973, Coal resources of 1 Colorado, 1972 summary of: Colorado Geol . Survey Spec . Pub . no. 3, 15 p. 21 Hutton , T . , 1956 , Deep hole closes Lafayette street as old mine caves in : Denver Post1. , May 27 , 1956 . I King, H . J . , and Whetton , J. T. , 1958, Mechanics of mining subsidence : Colliery Eng. , v . 35 , no . 6 , p . 247-252 and i no. 7 , p. 285-388. Landis , E. R. , 1959 , Coal resources of Colorado: U.S. Geol . '4, Survey Bull . 1072-C, p . 131-232 . Litwiniszyn , J . , 1958, The theories and model research of movements of ground masses : Colliery Eng. , v . 35 , no . 10 , p. 438-444. lla Lowrie , R . L . , 1966 , Analysis of the coal industry in Boulder- Weld coalfield, Colorado: U.S . Bur . Mines Rept. Inv. 6726 , 79 p . Malde , H . E. , 1955, Surficial geology of the Louisville 1 _i quadrangle , Colorado : U .S . Geol . Survey Bull . 996-E, :I p . 217-257 . I Martin , S . C. , 1910, Coal of the Denver basin , Colorado: U. S . Geol . Survey Bull . 381-C, p . 297- 306 . . . Mohr, H . F. , 1956 , Influence of mining on strata: Mine and dQuarry Eng . , v. 22, no. 4 , p . 140-152. j r , ,[ S 2.1 6,s^in 4. e. Al q X-2 1 '4,4 National Coal Board, 1966 , Subsidence engineer' s handbook: National Coal Board - Production Department, London , 118 p . Panek , L . A . , 1973, Program for control of surface subsidence : U. S . Bur. Mines Prog. Rept. , no . 10011 , 23 p . µ' Perez, W. , 1958, Subsidence observations in Austria: Colliery Eng . , v. 35 , no. 11 , p . 479-482 and no. 12 , p . 533-535 . Scott, G. R . , 1962, Geology of the Littleton quadrangle, Jefferson, Douglas , and Arapahoe Counties , Colorado: U.S . Geol . Survey Bull . 1121 -L , 53 p . Smith , R. 0. , Schneider, P . A. , Jr. , and Petri , L. R. , 1964, Ground water resources of the South Platte River basin in western Adams and southwestern Weld Counties , Colorado : U.S . Geol . Survey Water-Supply Paper 1658, 132 p . Soister, P . E . , 1965 , Geologic map of the Fort Lupton quad- rangle , Weld and Adams Counties , Colorado : U. S . Geol . Survey Geol . Quad. Map GQ-397 . 1965 , Geologic map of the Hudson quadrangle , Weld and Adams Counties , Colorado: U . S . Geol . Survey Geol . Quad . Map GQ-398. 1965, Geologic map of the Platteville quadrangle , Weld County, Colorado: U .S . Geol . Survey Geol . Quad. Map GQ-399 . Spencer, F. D. , 1961 , Geologic map of the bedrock geology of the Louisville quadrangle , Colorado : U. S . Geol . Survey Geol . Quad. Map GQ-151 . c Stefanko, R . , 1973, Subsidence and ground movement, in S .M.E . handbook: Soc. Mining Eng. , Am. Inst. Mining , Ft. ands Petr. Eng. , Inc . , New York , p. 13-2 to 13-9. Turnbull , 0. , and Potts , E. L. J . , 1958 , Surface and underground subsidence correlation : Colliery Eng . , v. 35 , no . 2 , p. 65-72. Van Horn , R. , 1957, Geologic map of the bedrock geology of the Golden quadrangle , Colorado : U .S . Geol . Survey Geol . Quad. Map GQ-103. Weimer , R . J . , 1973, A guide to uppermost Cretaceous stratig- raphy, central Front Range , Colorado : Mountain Geologist , v . 10 , no . 3, p . 53-97 . X-3 1I. S1 9 'a 1 Wells , J . D. , 1967, Geology of Eldorado Springs quadrangle , i Boulder and Jefferson Counties , Colorado: U.S . Geol . I Survey Bull . 1221-D, 85 p. Woodhuff, S . D . , 1966 , Methods of working coal and metal mines , : 1 Vol . 2, Ground support methods : New York, Pergamon Press , 429 p . I i Yinst, P . 0 . , 1960 , Coal resources of Colorado: Colo. Sch . Mines Min . Ind . Bull . , v . 3, no. 5 , 8 p . ' ; ' Young , C . M. , 1917, Percentage of extraction of bituminous coal with special reference to Illinois conditions : Univ . Illinois Engineering Experiment Station Bull . 100 , 175 p . I Young, L. E. , 1916 , Surface subsidence in Illinois : Illinois Geol . Survey Bull . 17 , 112 p. , I and Stoek, H. H . , 1916 , Subsidence resulting from mining : Univ. Illinois Engineering Experiment Station Bull . 91 , 205 p . I Zwartendyk, J . , 1971 , Economic aspects of surface subsidence resulting from underground mineral exploitation [Ph . D . t; thesis] : University Park , Pennsylvania State Univ . , 4 University Microfilms , Ann Arbor, 411 p . _ .�' ,`Y ,i,fi c} ^, .- .. u . :' 1 :tk 1 ar j ' I . i ' CA X-4 91 fil 9 Y I „al -" CONCLUSIONS • 1 . Much of the land between the towns of Marshall (Boulder • County) and Firestone (Weld County) is now undermined with abandoned coal workings . 2. The workings lie at depths which range from 30 to 580 feet. Most are within the 100 to 300 foot depth range . 3. The coal mines were worked by the room-and-pillar . method rather than by the longwall method . In most cases , the miners attempted to "pull " as many of the pillars as they could during the later stages of development in any given mine . 4. Most of the theories of coal mine subsidence and most of the methods of predicting the time , duration , and extent of subsidence are derived from European experi - ments and observations in longwall mines . These theo- ries and predictive methods are not entirely applicable to the room-and-pillar mines of the Boulder-Weld coal - field. This is because the presence of unpulled pillars (even in so-called "worked out" mines) disrupts the or- derly development of subsidence and introduces a great deal of uncertainty as to the time of subsidence rela- - tive to the time of mining . i ei. r> IX-1 5 . The extent of subsidence in the coalfield can be fairly well defined by field observations . Strong evidence of surface subsidence consists of well -defined pits and ! depressions; less definitive evidence consists of broad ! swales and shallow, poorly drained depressions . 6. Unequivocal evidence of subsidence is often observed on ' the surface in those areas where the mining depths do not exceed 200 feet. In areas where mining depths are ' greater, surface subsidence is not readily observable by the unaided eye , even though its presence could log- ically be expected. Precise surveying in such areas might detect shallow, closed depressions and might show that previously established benchmarks have subsided . 7 . Observed damage to homes , streets , buildings , highways , and irrigation ditches should not automatically be as - cribed to subsidence because, in many cases , the damage could be induced in other ways . 8. Interviews with local residents and miners are often helpful in locating surface subsidence features and in determining the time and duration of subsidence occur- rences . However, it should be noted that memories of events which occurred 30 to 40 years ago are sometimes IX-2 �I 3 uncertain , and that reports of subsidence must be cross-checked through field observations or through other interviews . ^r E ' 9. In some cases Federal government aerial photography is helpful in studying subsidence in the coalfield . Because the scale (1 "=1667 ' , 1 : 20000) of these photos is quite small , relative to the size and depth of the __ - . subsidence features being investigated , interpretation of subsidence is often uncertain . Nevertheless , a study of various sets of aerial photo coverage taken over the years (1937-1969) by different government agencies could provide a rough historical record of subsidence development in the coalfield since the late 1930 ' s . 10. Low-sun-angle aerial photos , taken early in the morn- • y ing, are a decided improvement on the normal government photography because the long shadows cast at that time of day enhance the outlines of low-relief subsidence features . In the detection of subsidence , the low-sun- angle photos are not a significant improvement over on-the-ground field observations . 11 . There appears to be little correlation between instances of surface subsidence and other mining factors such as 4 IX-3 depth of cover, presence or absence of pillars , and probable thickness of extracted coal . There does seem to be a relationship between cases of surface subsidence and depth of cover coupled with the presence or absence of pillars . • 12 . A classification of "severe, " "moderate , " and " low" hazard has been adopted for all undermined areas in the coalfield. These areas and their ratings are shown on a subsidence hazard map. The three categories of hazard are based on estimations of the relative amount of danger to which persons and structures in a given area might be subjected should subsidence occur in the future. 13. When specific properties in the coalfield are con- sidered for development, an examination of the subsi - dence hazard map will give a first approximation as to the feasibility of the project. In most cases , more detailed information than is given in this re- port will have to be acquired. Much of this data will have to be derived from test drilling and geophysical surveys and its acquisition will undoubtedly be expensive. F. IX-4 C.11r€ 'J . Hello