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Home My WebLink About800849.tiff RESOLUTION RE: APPROVAL OF GEOLOGIC HAZARD DEVELOPMENT PERMIT #4 : 80 : 3 - MICHAEL COUFAL. WHEREAS, the Board of County Commissioners of Weld County , Colorado , pursuant to Colorado statute and the Weld County Home Rule Charter, is vested with the authority of administering the affairs of Weld County , Colorado , and WHEREAS, on April 9 , 1980 , the Board of County Commissioners of Weld County, Colorado approved a Conditional Use Permit for a single family dwelling and small farm operation for Michael Coi- fal with the condition that he comply with the Weld County Geo- logic Hazard Regulations, and WHEREAS, Michael Coufal has submitted the required supple- mentary plans , maps , reports and data, and WHEREAS, Michael Coufal has requested approval of a Geolo- gic Hazard District Development Permit on property described as the North Half of the North Half of the Southwest Quarter of Section 15, Township 1 North, Range 68 West of the 6th P. M.. , Weld County, Colorado , and WHEREAS , the Board of County Commissioners has studied the recommendations of the Weld County Planning staff and the Geolo- gic Investigation Report of E. O. Church, Inc. , and finds that the request is in compliance with the purpose and intent of the Weld County Geologic Hazard District Regulations , and WHEREAS, the Board of County Commissioners further finds that Michael Coufal has complied with the condition of approval contained in the Conditional Use Permit and that the request for a Geologic Hazard Development Permit should be approved sutject to the applicant complying with the recommendations of E. O. Church, Inc. contained in its Geologic Investigation Report , Job No. 254 , dated June 5, 1980 . NOW, THEREFORE, BE IT RESOLVED by the Board of County Com- missioners of Weld County, Colorado that the Board finds that Michael Coufal has complied with the condition specified ir the n'5Jzst.. /it .//. eneltil,00 --- s 1100 m ��o RICHARD D. L.AMM t Y°` # JOHN V/ TOLD GOVERNOR t�,_ ** Direc.ar 78 16 COLORADO GEOLOGICAL. SURVEY DEPARTMENT OF NATURAL RESOURCES 715 STATE CENTENNIAL BUILDING — 1313 SHERMAN STREET DENVER,COLORADO 80203 PHONE (3031839-2611 July 9, 1980 Ms. Vickie Traxler Weld County Department of Planning Services 915 10th Street Greeley, CO 80631 Dear Ms. Traxler: RE: COUFAL GEOLOGIC HAZARD PERMIT WELD COUNTY We have reviewed the Coufal Geologic Hazards Overlay District Development Permit and geologic investigation by E. 0. Church, Inc. Mr. Church' s investigation indicates that there is low risk of damage to a properly designed residential structure. If his recommendations for residence, well and individual septic system construction are closely observed, we have no objection to approval of this application. Sincerely, c . Julia E. Turney E-giineering Geologist JET/gp cc: LUC f'1g9t0 s JUL 198D RECEIVED f .1, r. N'e if/11,11' 1,C u .' GEOLOGY STORY OF THE PAST . . . KEY TO THE FLTU RE Conditional Use Permit for a single family dwelling and small farm operation. BE IT FURTHER RESOLVED by the Board of County Commissioners of Weld County, Colorado that Geologic Hazard Development Permit 44 : 80 : 3 be, and hereby is, approved subject to the applicant complying with the recommendations of E. O. Church, Inc . con- tained in its Geologic Investigation Report: , Job No. 254 , dated June 5, 1980. The above and foregoing Resolution was , on motion duly made and seconded, adopted by the following vote on the 16th day of July, A.D. , 1980. r• t t 4 4`\ -.- . . ' BOARD OF COUNTY COMMISSIONERS ATTEST : WELD COUNTY/ COLORADO Weld County Clerk and Recorder 4/: // ' (Aye) and Clerk to the Board C. W. Kirby, /Chairman (By:_ ,. . ,./t `/ , , &.„l - �nnW�C� l," (Aye) eputy Count" Clerk 1 onard i I . Roe, Pro-Tem / -APPlth,ED AS TO FORM: G.� (Aye) 'yrwt+.� �C - Norman Carlson 1✓ County Attorney , ._� (Q (Aye) /Kf/1 D unbar / j«-/„Z ' 4-4../.eAt;J/ / :''`(Aye) ze K. einmark DATE PRESENTED : JULY 21 ,. 19E0 REFERRAL LIST • LO p APL ::ANT Michael Coufal • CASE r G1-1-4:80:3 REFERRALS SENT OUT 0II: June 24, 1980 F� v REFERRALS TO BE RECEIVED BY: July 1 I , 1980 c, ra —--- 0 U 0 1-t P, U • C) U z .771 O � c REFERRALS RECEIVED e1 /t utsxh/Lxx ixa r7.!txyx 'x. " '0 I . County Health ! - . 2. Count_, Engineer . 3. Calorac:o Geological Survey • Attn: Jul la Turney a 1313 Sherman Street S.I1• ' 3 `in Room 703 Denver, Colorado 80203 • - DEPARTMENT OF PLANNING SERV CES PHONE (303; 3564000 x.404 915 10TH£'REET GREELEY COLORADO 30631 July 16, 1980 11111111e. COLORADO tovgtr Board of County Commissioners � c Jv� ti ~ Weld County Colorado 915 10th Street �F• Greeley, Colorado 80631 Re: Geologic Hazard Development Permit #4:80:3 Dear Commissioners: The attached report, letters and maps are in reference to a request from Michael Coufal for approval of a Geologic Hazard District Development Permit on property described as the N1 N1 SW1, Section 15, T1N, R68W of the 6th P.M. , Weld County, Colorado. This property is located 21 miles east of Erie. On April 9, 1980 the Board of County Commissioners approved a Conditional Use Permit for a single family dwelling and small farm operation with the condition that the Coufals comply with the Weld County Geologic Hazard Regulations. The applicant has submitted the required supplementary plans, maps, reports, and data. This material has been reviewed by the Colorado Geological Survery, Weld County Health Department, Weld County Engineering Department and County Depart- ment of Planning Services. Based upon the information submitted and the adopted policies in the County the Department of Planning Services Staff recommends the request be approved for the following reasons: 1. The Geologic Investigation report by E. 0. Church, Inc. indicates that there is low risk of damage to a properly' designed residential structure. The Colorado Geological Survey has no objection to the approval of this request if the applicant follows the recommendations for residence, well , and individual septic system construction contained in the E. 0. Church, 11 Inc. Geologic Investigation Report. 2. The Weld County Health Department and Engineering Department has set forth no objections to this request. 3. It is the opinion of the Department of Planning Services Staff that the request is in compliance with the purpose and intent of the Weld County Geologic Hazard District Retulations, which state in part, that the adverse impacts of geologic hasards on life and property shall be reduced by providing for geologic hazard investigation and mitigation of adverse impacts of such hazards at the time of initial construction. ,,.J 11 -t.) i.. 1 v. SITE �-' !, SCALE 1" 3000' -.y EXPLANATIONS: SEVERE HAZARD LOW HAZARD I j NO SUBSIDENCE HAZARD MAPPED FROM: ENVIRONMENTAL GEOLOGY NO. 2 GROUND SUBSIDENCE AND LANDS USE CONSIDERATION'_ OVER COAL MINES IN THE BOULDER-WELD COAL FIELD, COLORADO PLATE 6 , AMUEDO AND IVEY FOR THE COLORADO GEOLOGICAL SURVEY 1975 1 .1 SUBSIDENCE HAZARD MAP ] FROM ENVIRONMENTAL GEOLOGY NO. 9, COLORADO GEOLOGICAL SURVEY 1 JOB NO. 254 FIG. 2 Board of County Commissioners July 16, 1980 Page 2 The Department of Planning Services recommendation for approval is conditional upon the applicant complying with the construction recommendations in the E. 0. Church, Inc. Geologic Investigation report, Job No. 254, dated June 5, 1980. Respectfully submitted, eSka• CIP0431L4*".. Chuck Cunliffe Assistant Zoning Administrator GC:rg .O.�r•• rrs,^ • :JO'Y • :CIEAT IF i:—t:N:' :E%. .C WEPT. - -• •> -a.-34 'hV!RL Y• - C A C PUP! .JL..E0. SEC 15 i6 ;'IN.. R.68W — r. .Z. .f. .'s'. ::.•1•14.1C :.L.••••; C 'aka 4.• t! _ • • • • -�'.'i •'.. :�.�.�• v:.I P S:lJe - 1'..r.1 Ii i T MAP - . - - • • s. -C Ac J j • • • rI . S;TE PLAN E E. O. CHURCH, INC. \ O • CONSULTING GEOLOGICAL ENGINEER J\ C .., 165 MADISON STREET • SUITE 0 • DENVER, COLORADO 80206 • (303) 321-8417 .oq; -.7 GEOLOGIC INVESTIGATION PROPOSED COUFAL RESIDENCE --a 40 ACRE TRACT NORTH 2, NORTH 1, SOUTHWEST a 1 SECTION 15, TIN, R68W WELD COUNTY, COLORADO - n�� v+, rte. •,IFSr. i .- tc- kolt StAIu 8L 9 9r' • Prepared For: Mr. and Mrs . Michael Coufal 9930 Weld County Road, No. 28 Platteville , Colorado 80651 I Job No. 254 June 5, 1980 `1 4 _1 1 H nJ OUR INVESTIGATION INDICATED THERE IS A LOW RISK OF S_ESIDENCE DAMAGE FOR CONSTRUCTION OF A SINGLE FAMILY RESIDENCE AND APPURTENANT FACILITIES WHEN DESIGNED AND CONSTRUCTED ACCORDIND -0 RECOMMENDATIONS DISCUSSED IN THE REPO--. • .1 ti \\ - -.. \ \� ' a -4- 403 UQ ✓ V i \ i" \ I \ I JOB NO. 254 TABLE OF CONTENTS SCOPE 1 CONCLUSIONS 1 SITE CONDITIONS 1 PROPOSED CONSTRUCTION 2 A GEOLOGIC SETTING 2 GEOLOGIC HAZARDS 3 1 CONSTRUCTION RECOMMENDATIONS 5 Residence Construction 5 ..l Well Construction 6 ISDS Construction 6 LIMIATATIONS 7 FIG. 1 - SITE PLAN FIG. 2 - SUBSIDENCE HAZARD MAP Wd -1 .l -. 7 structing the absorption field a minimum of 1 foot below floor drains and the septic tank. We recommend that the sewer lines be constructed with a minimum slope of 3% rather than the typical 1.5% grade. The increased slope is recommended because in case of minor subsidence, the increased slope will reduce the risk of the reversal of slope of the sewer line which would cause backing up of the sewer line. LIMITATIONS Our investigation was based on a review of published literature and data available through public and private concerns . No original field data collectior. was performed as a part of this investigation. We recommend the inspection of the water well drilling process to confirm data collected as a part of our investigation. In addition, specific design and construction recommendations in the AA Engineers Report No. 80122 dated May 30, 1980 should be utilized and in- spected. If we can be of further service in discussing the contents of this report or in analysis of the proposed constructior from a geologic point of view, please call . E.O. CHURCH, INC. 6)>E4Ate Edward 0. Church P.E. r -. 1 7 Geological Engineer - " EOC/sc 1 (3 copies sent) cc: AA Engineers 888 South Lipan •.� Denver, CO 80223 - SCOPE This report presents the results of a geologic investigation for a 40 acre tract which is the north 1, north, southwest ', Section 15, TIN, R68W, Weld County, Colorado. The report presents a description of geologic conditions , existing underground mine conditions , and recommendations for the construction of the proposed residence and appurtenant facilities which are influenced by geologic conditions . The report was prepared on the basis of data developed during research and field investigations, as well as our experience with similar conditions . CONCLUSIONS 1. The near surface soil and bedrock consists of clay and claystone of the Cretaceous Laramie Formation. There are scattered sandstone and lignite beds interlayered in the claystone . The lower 80 to 125 feet of the • Laramie Formation, which occurs at depths of 275 to 400 feet at this site, consists of sandstone, shale and several coal beds. The Fox Hills Formation, which is the primary aquifer in the area , underlies the Laramie Formation with wells penetrating typically to depths ranging from 400 to 600 feet in the area. 2. Potential geologic hazards in the area include near surface ex)ansi4e clay and claystone bedrock and a subsidence hazard associated with underground coal mine operations . 3. We believe a single family residence may be constructed at this site _1 with a low risk of damage. The residence, well and individual sewage disposal system (ISDS) should be constructed as recommended in this report. In general , an engineered foundation system designed to resist expansive soils and bedrock should be installed to resist the swell potential . The potential for damage due tc subsidence can be reduced . a properly constructed residence, ISDS and domestic well . Tie drillin of the domestic well should be inspected by a representative of our office. 1 Y SITE CONDITIONS The investigated site is a 40 acre parcel of agricultural land. The site slopes gently to the east-northeast at grades ranging from 3% to 5%. At the time of our investigation the site was vacant of structures and was being uti- -6- tions. We recommend that the attached garage at this location be isolated on a separate foundation. We recommend a wood framing system and wood con- struction above grade. Cinder block, brick and brick veneer should be avoided. Wood type construction is relatively flexible and can absorb • slight movement with little or no damage to the structure. A floating floc -fl system typical of construction on expansive soils is also well adapted to areas of potential subsidence and should be constructed at this site. A system which will provide flexibility in utility lines is manditory. The flexibility must be designed into all below ground utilities which may include any or all of gas , electric , water and sewer services . If the services go through foundation walls, we recommend a minimum of 4 inches of movement in all directions where the utility passes through the wall . If the utility goes through a floor slab, differential movement between the utility and the slab must be possible. In design of the structure , we reconme nd that, where possible, doors be staggared rather than being aligned on opposite walls and that large picture windows be held to a minimum. 1 Well Construction•.4 Well construction at this site will be relatively expensive . The entire site has been undermined according to mine records and no large pillars exist through which a domestic well can be inexpensively drilled. 1 We anticipate that the well will have to be cased and cemented to a depth on the order of 375 to 400 feet, from which depth more normal drilling wil ' be possible to the Fox Hills aquifer. We anticipate that the total depth of the well will range from 500 to 600 feet. ISDS Construction There are no unusual design requirements for the ISDS other than con- -2- lized as an alfalfa field. Trees to provide landscaping and a windbreak had been planted near the northwest corner of the property. There are several drai- nage ditches which cross the property as shown on Fig. 1. There is no evidence of subsidence from underlying mine workings such as potholes or depressions in the proposed building area. .j PROPOSED CONSTRUCTION A single family residence with appurtenant well and individual sewage dis-• posal system ( ISOS) and barn are proposed at. this site at locations shown on Fig. 1. The proposed residence is to be a one story house with a full basement and attached garage. There is a 8 inch water main in the county road adjacent to the property, but the Left Hand Water District, which owns the water line, does not have sufficient water to sell taps. 1 GEOLOGIC SETTING The investigated 40 acre site is located east of the Front Range of the Rocky Mountains in an area which is subject to slow erosion. There is thin (less than 3 feet) eolian silt and sand deposits underlain by stiff clay soils . Bedrock in the area consists of claystone with interlayered sandstone and ligni ' e of the Cretaceous Laramie Formation underlain by sandstone of the Fox Hills Formation at depths of 400 to 500 feet. Of specific concern at this site is the coal which occurs in the lower 80 to 125 feet of the Laramie Formation. The coal underlying the site has beer mined by underground methods which will be discussed later in the report. Lite -- ature indicates that approximately 80 feet above the coal seams is a relatively competent sandstone layer which is used as a marker bed in the formation. rl my 1 <H. -5- and pillar mining rather than Longwell mining was utilized in the Boulder-Weld coal field, we believe there is only a slight potential for damage to the pro- posed residence . Expansive soils and bedrock are common problems along the Front Range of 1 a The Rocky Mountains. Engineer designed foundation systems are available to 1 reduce the risk of hazards associated with swelling soils and bedrock. The soils and foundation investigation performed concurrently with this study by wl AA Engineers provides specific design and construction details for construction on expansive soils. -1 CONSTRUCTION RECOMMENDATIONS Our investigation indicates that the proposed single family residence and appurtenant facilities can be constructed at this site with a low risk of damage to construction. Design and construction recommendations are given below for three construction areas which include the residence , the well and the individua sewage disposal system. j Residence Construction There are two possible construction methods generally acceptable in areas of potential subsidence which include a flexible foundation and a rigid foundation. Considering the added potential hazard of expansive soils, we recommend the utilization of a rigid foundation system at t:Fis . 4 site. The rigid foundation system would be similar to the drilled pier foundation system recommended in the AA Engineers ' report. The type cf 1 residence planned at this site with a full basement is a relatively rigid 3 structure and, therefore, adapts well to this type of construction . We specifically do not recommend split level type construction where the stru :- _.3 ture is broken at several different levels and has variable loading condi- -] -3- GEOLOGIC HAZARDS There are two primary geologic hazards which exist at this site and include a potential for subsidence due to underground coal mining at the site, and 1 expansive soils . Each of the potential geologic hazards will be discussed be- . low and recommendations will be discussed later in this report. "j Our investigation of the coal mining in the area included review of litera- 1 ture and acquisition of data including: (1) Coal Mine Subsidence and Land Use .j Over the Boulder-Weld Coal Field, Boulder and Weld Counties , Colorado, Colorado Geological Survey, Engineering Geology Publication Number 9 by Amuedo and Ivey, Geologic Map of Boulder, Fort Collins , Greeley Area, USGS Map I 855-G by Roger B. Colton, and the review of mine maps for the Eagle Mine at the Colorado Division of Mines, the US Bureau of Mines Map Repository, and the Sunflower Energy Company (the operator of the Eagle Mine) . Our review of literature and maps indicates the Eagle Mine which was operated by the Imperial Coal Company (a subsidiary of Sunflower Energy Company) undermined most of Section 25 . The specific area of the investigated site was entirely undermined using the room and pillar mining method. Approximately 10.4 feet of coal was removed at a 1 depth of 355 feet below the proposed residence . The map indicated at least 67% rl of the coal was extracted with 33% of the coal left as pillars . The records indicate that the mining beneath the proposed residence was done in 1948, and that mining in the eastern most portions of the 40 acre parcel was done as late as 1956. Results of the Amuedo and Ivey investigation indicate there are low ani 4 severe risk hazards areas within the property as shown on Fig. 2. Two specific. items in the Amuedo and Ivey report indicate that "local miners who have worked. in the . . . Eagle . . . report that while the roofstone of these mines is prone to 1 collapse, an "ironstone" layer occuring 12 to 80 feet above the mine workings tends to stop further upward caving" and "soft shale and clay floors were reported 1 in the . . . Eagle . . . . . . . It should be anticipated that mines with hard floors -4 -4- and standing pillars may have a greater percentage of remaining voids than those with soft floors . " The indication from the Amuedo and Ivey report is that at the Eagle Mine subsidence is relatively rapid after the area is mined. The subsidence or caving at the Eagle Mine is anticipated to move upward to an "ironstone" layer consisting of quartsite sandstone 12 to 80 feet above the mine ri workings . The severe risk areas identified on Fig. 2 by the Amuedo and Ivey inves- t tiigation are due to adjacent unmined areas . A 1976 map available at Sunflower Energy Company indicated all adjacent areas were mined which would increase the size of the low risk areas on the Amuedo and Ivey report to include all of the subject site. The potential for subsidence at the area of the proposed residence was analyzed by several methods which indicate there is a low subsidence hazard risk at the property. The first method which assumes a 10% bulking in material which subsides indicates that for an extracted layer of 10.4 feet subsidence will progress only approximately 100 feet above the extracted coal seam. Con- sidering that 33% of the coal was left in the ground and that the mining was done at a depth 350 feet, this method indicates that there should not be surface subsidence at the proposed residence location. A second, more sophisticated method of analysis, established by the British National Coal Board, was then used to analyze the site. As discussed in the Amuedo and Ivey report, the National Coal Board analysis does not give irrefutable results because th 1 method is based on the Longwell method of mining rather than the room and pillar method utilized in the Boulder-Weld coal field. The National Coal Board method 1 indicated strains ranging from 0.0012 to 0.007. The strains , when analyzed wit respect to the size of structures proposed at this location, indicate a slight to appreciable potential for problems. When considering that (1) the unadjustei 1 maximum extracted coal seam thickness was used in the analysis and that (2 roam Hello