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Home My WebLink About950503.tiff M Eoc EXHIBIT B E.O. CHURCH, INC. ENGINEERS & GEOLOGISTS I SOILS AND FOUNDATION INVESTIGATION PROPOSED KEENESBURG ONECOMM TOWER AND STRUCTURE NW/4, NW/4 , SECTION 27 , T2N, R64W WELD COUNTY, COLORADO • Prepared for: ONECOMM, ATTN: LINDA AUGUSTINE 4643 SOUTH ULSTER STREET, SUITE 500 DENVER, CO 80237 NOVEMBER 14 , 1994 JOB NO. 5690 950503 • P.O.Box 2869 • Ev9rgreen, Colorado 80439 925E 932- 69 Avenue •F Colorado 80218 (303) 674-0660 FAX(303) 674-0813 ' (303) 832.9692 FAX((30 0 3)832-3517 I d 11 TABLE OF CONTENTS 1 1 SCOPE 1 CONCLUSIONS WiPROPOSED CONSTRUCTION 1 VM I SITE CONDITIONS 2 2 3 INVESTIGATIONS SUBSURFACE Fri CONDITIONS TOWER FOUNDATIONS 3 4 LATERAL LOADS Ir. I SERVICE BUILDING FOUNDATIONS 10 SLAB-ON-GRAD E CONSTRUCTION 4 SURFACE DRA Pillia INAGE 5 LIMITATIONS Ply_ EXPLORATORY BORINGS ri FIG. 1 - LOCATION OF TORY BORINGS FIG. 2 - LOGS OF EXPLORATORY FIG. 3 - SWELL-CONSOLIDATION TESTS ill 950503 EN AI SCOPE This report presents the results of a soils and foundation inves- IIItigation for a ONECOMM Communication Tower and service building to be located in the NE/4, NE/4, Section 27 , T2N, R64W, Weld County, Colora- do. The report presents a description of the subsurface conditions DMencountered at the site, recommended foundation system, ground water, and design and construction criteria influenced by the soils . The NIreport is based on data determined during the field and laboratory investigations and our experience in the area. A summary of our find- DMings and recommendations is presented below. SICONCLUSIONS 1 . Subsurface conditions encountered consisted of 12 feet of 1$ silty clayey sand underlain by medium hard to hard claystone and sandstone bedrock to the maximum depth explored of 20 and 35 feet. The claystone bedrock exhibits a moderate swell potential . II2 . No free water was encountered in the borings at drilling. 3 . The tower can be founded on either a mat/block foundation or III a drilled pier foundation. Design and construction criteria are given in the report. ON 4 . The soil possess a slight swell potential and the owner must be willing to accept the risk of movement of slab-on-grade con- struction. We recommend slabs be free to move vertically. ill5. Good surface drainage should be established and maintained at all times. .114 PROPOSED CONSTRUCTION iliA 160 foot high free standing three sided lattice type tower is proposed as indicated on Fig. 1 . A 12' X 20' precast concrete vault, .ill used as a service structure, will be located as indicated on Fig. 1 . Relatively light construction loads are anticipated. N SITE CONDITIONS 950503 MIThe site is located in an agricultural area southwest of County Roads 18 and 57, northwest of Keensburg in Weld County, Colorado. The 2 site is an existing agricultural field with a drainage gulch running north to south along the east portions of the site. The proposed tower and structure will be located in the highpoint of the site west of the drainage gulch. The site includes .a gentle slope to the south. INVESTIGATIONS . Subsurface conditions were investigated by drilling 2 exploratory borings at the locations indicated on Fig. 1 . The borings were advanc- ed using a 4 inch diameter continuous flight auger powered by a Mobile 1 B-57 drilling rig. Samples were taken at general 5 foot intervals us- ing a California sampler which was driven into the soil by dropping a 140 pound hammer through a free fall of 30 'inches . The California sam- pler is a 2.5 inch outside diameter by 2 .0 inch inside diameter de- vice. The number of blows required to drive the sampler into the soil is known as a penetration test. The number of blows required for the sampler to penetrate 12 inches can be evaluated and gives an indica- tion of the consistency or relative density of the soils and bedrock. The results of penetration tests and logs of the soils encountered are presented on the Logs of Exploratory Borings, Fig. 2 . Samples were returned to the laboratory where they were visually classified and appropriate testing assigned to evaluate the engineering properties of the soil layers. Laboratory testing consisted of two swell-consolida- tion tests. The results of the laboratory testing are presented on Figs. 2 and 3 . I SUBSURFACE CONDITIONS Subsurface conditions encountered consisted of 12 feet of silty clayey sand underlain by medium hard to hard claystone and sandstone bedrock to the maximum depth explored of 20 and 35 feet. The claystone 950503 3 INpossesses a low to moderate swell potential . No free water was en- countered in the borings at the time of drilling. EM TOWER FOUNDATIONS In our opinion the tower can be constructed with either a mat- Olliblock foundation or a drilled pier foundation system. The mat/block foundation system should be designed for a maximum allowable soil MINbearing pressure of 2500 pounds per square foot (PSF) . The tower can also be constructed with a drilled pier foundation system. The drilled MIpier foundation system can include one large diameter pier or a series 11111 of three smaller diameter piers designed and constructed to meet the following criteria. 1 . Piers should be designed for a maximum allowable end bearing pressure of 25,000 pounds per square foot (PSF) and an allowable skin friction of 2500 PSF for the portion of pier in bedrock. UM2. The piers should have a minimum penetration into bedrock of 8 feet. We recommend a minimum length of piers of 20 feet. gill3 . All piers should be reinforced full length with at least three No. 5 bars to resist tension in the event of swelling . Reinforcement should extend into grade beams of foundation walls . 4 . We believe piers can be installed using the "drill and pour" method of drilling. Concrete must be onsite at the time of drill- ing and placed immediately after drilling. Installation of the piers should be observed by a representative of our office to an confirm piers are bottomed in suitable material and the holes are Iliproperly cleaned. MILATERAL LOADS The upper soils will react to lateral loading of the tower. We recommend the top 3 feet of soil not be used in the analyzing of 1a-t- ill eral loads due to disturbed conditions. For this site, we recommend IIIan "active" equivalent fluid pressure of 40 pounds per cubic foot (PCF) and a "passive" equivalent fluid pressure of 400 PCF. ijil 111 950503 4 SERVICE BUILDING FOUNDATIONS The proposed service building is a prefabricated concrete struc- ture. It is a rigid box type design which can tolerate differential movement. We believe the building can be: 1 . placed directly on the existing soil, 2 . placed on a concrete slab, or 3 . a drilled pier foundation. If a permanent foundation is required, we recommend a drilled pier foundation system. A drilled pier foundation should be designed with the same criteria as the tower foundation. I SLAB-ON-GRADE CONSTRUCTION The upper soils possess a low expansive potential and there is the risk of movement of slab-on-grade construction. The owner must be willing to accept the risk of slab movement if slab-on-grade construc- tion is used. If new fill is required beneath slabs, we recommend the onsite soils be compacted to a minimum of . 95% of standard Proctor den- sity as determined by ASTM 698 . We recommend slabs be constructed as "floating" slabs which are free to move in a vertical direction. SURFACE DRAINAGE The risk of wetting of foundation soils can be reduced by care- fully planned and maintained surface drainage. We recommend the fol- lowing precautions be observed during construction and be maintained at all times after the structure is completed. 1 . Excessive wetting or drying of open foundation excavations should be avoided as much as possible during construction. 2. Backfill around foundation walls should be moistened and com- I pacted. Any settlement of backfill structure should be . immedi- ately filled and positive drainage re-established. 3 . The ground surface surrounding the exterior of the structure should be sloped to drain away from the structure in all direc- tions. We recommend a minimum slope of 12 inches in the first 10 feet.. 950503 5 4 . Roof downspouts and drains should discharge well beyond the limits of all backfill. 5. Plastic membranes should not be used to cover the ground sur- face immediately surrounding the structure. These membranes tend to trap moisture and prevent normal evaporation from occurring. LIMITATIONS Although the borings were located to obtain a reasonably accurate determination of foundation conditions, variations in the subsoil con- ! ditions are always possible. If conditions different from those des- cribed in this report are encountered in the completed excavation, we recommend that the excavation be observed by a representative of our office. The installation of piers should be observed by a representa- tive of our office. If we can be of further service in discussing the contents of this report, or in the analysis of the influence of subsurface condi- tions on the design of the structure, please call . E. O. CHURCH, INC.NI Edward O. Church, 'P.E. EOC/jg 2 copies sent cc: Kennith Clark, Architect cc: Structural Consultants, ATTN: Loren Lieberman I I I I 950503 ONECOMM KENNSBURG SITE NO 0 ALE NE/4. NE/4. SECTION 27. T2N. R64W WELD COUNTY. COLORADO • tn c s ROAD I8 •7H-I PROPOSED TOWER AND STRUCTURE • TH-2 1-70 • KEENSEURG SITE PLAN AND LOCATION OF EXPLORATORY BORINGS DB NO. 5690 950503 I I _ TH-I TH-2 o • • •▪ 15/12 '. 'VC. WC - 11.0 5 ll - DD - 88 F- _ w w . LL - - J- l J _ w z 17/12 30/f2 A- li,' _ 2 _l 50/12 WC - 142L. - DD - III . _ - - O ' 50/C I '0 25 50/10 - EXPLANATIONS; I _ • -jSAND. CLAYEY. SILTY TO CLA'r'. SAND'( DENSE. MOIST. TAN. FROWN (SC-CL) 30 CLAYSTONE BEDROCK. HARD. MOIST 1 GRAY. OLIVE. BROWN 15/12 INDICATES THAT 15 BLOWS OF A 140 - -. - POUND HAMMER FALLING 30 INCHES WERE - _ REQUIRED TO DRIVE A 2.5 INCH 0.D. SAMPLER 35 50/7 12 INCHES. I NOTES.. II THE EXPLORATORY BORINGS WERE DRILLED ON H-10-94 USING A 4-INCH DIAMETER CONTINUOUS FLIGHT AUGER POWERED BY A B-57 MOBILE DRILLING RIG. 2. NO FREE WA I ER WAS ENCOUN I EKED Al I HE I IME OF DRILLING I 3. WC • WATER CONTENT (e) DD - DRY DENSITY (PCF) • LOGS OF EXPLORATORY BORINGS JOB NO. 5690 - FIG . 2 950503 II N6C>."."-----------Th:::L.----"tj.NN II C 4 0 0 a 111 W2 a 0 \ - O2 EXPANSION UNDER CONSTANT NPRESSURE DUE TO WETTING E 4 0 I U 6 • 11 0.! 1.0 10 100 APPLIED PRESSURE — ksf ill Sample of CLAYSTONE from TH-1 @ 14 FEET Natural Dry Unit Weight = 111 pcf Natural Moisture Content : 14.2 percent II 3 c 2 al 0 N a w I IADDITIONAL COMPRESSION o 0 UNDER CONSTANT PRESSURE — Ill DUE TO WETTING c 1 21\ ll n 0 E 2 0 U 1 3 I0.1 1.0 10 100 APPLIED PRESSURE — ksf II Sample of SAND, SILTY from TH-2 @ 4 1' 1' Natural Dry Unit Weight = 88 pcf Natural Moisture Content : 11.0 percent. Ill JOB NO. 5690 950503 FIG. 3 Swell-Consolidation Test Results -aa/� (�� j 4VsOss • ^ ,- wfif r H ngrr ▪ M14m l+ 'fir. lr 'I - . tVf�Yy"� I t o �F t i <,,,c4ftc kaa5f c. 4 y h • th ...41,k••as My ti, + �s royt* y",r �v•Y � � x�..u. 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