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Home My WebLink AboutObservation of Pit Excavation Soils Report 10.05.16... H-P~'KUMAR Gcotochnical Engineering ! Engineering Geology Ma terials Testing I Environmenlal 5020 County Road 154 Glenwood Springs, CO 81601 Phone: (970) 945-7988 Fax: (970) 945-8454 Email: hpkglenwoodOkumarusa.com Office Locations: Parker, Glenwood Springs, and Silverthome, Colorado October 5, 2016 WRW Log Works Attn: Whit Whitaker I02 Deer Valley Drive New Castle, Colorado 8164 7 (wrw3@hotmail .com) Project No. 16 -7-376 Subject: Observation of Pit Excavations , Proposed Indoor Riding Arena, 893 County Road I 02, Garfield County, Colorado Dear Mr. Whitaker: As requested, a representative of HP/Kumar observed pit excavations at the subject site on August 26, 2016 to evaluate the soils exposed for foundation support . The findings of our observations and recommendations for the foundation design are presented in this repon. The services were performed in accordance with our agreement for professional engineering services to WRW Log Works, dated August 29, 2016. H-P Geotech (now H-P/Kumar) previously performed a geologic site assessment and preliminary geotechnical study for the proposed Hunt Ranch Subdivision and reported our findings June 9, 2006, Job No. l 06 0033. The proposed indoor arena will be 120 feet by 240 feet and located about 100 feet north of existing barns and north of County Road 102. About one foot of topsoil had been removed from the arena area and a pit excavated at each building corner prior to our site visit. At the time of our visit to the site, four explor,uory pil'i had been dug about 4 feet below the adjacent ground surface. The soils exposed in the pit consisted of medium stiff, sandy silty clay. Results of swell-consolidation testing performed on samples taken from the pits, shown on Figures I, 2 and 3, indicate the soils huve low compressibility under light loading at existing moisture conditions and low to moderate collapse potential (settlement under constant load) when wetted. The samples had high compressibility under increased loading af1er wetting. No free water was encountered in the pit excavations and the soils were slightly moist to moist. Considering the conditions exposed in the exploratory pits and the nature of the proposed construction, spread footings placed on the undisturbed natural soil designed for an allowable soil bearing pressure of 1,500 psf should be adequate for support of the proposed indoor arena. The exposed soils tend to compress when wetted and there could be some post-construction settlement of the foundation if the bearing soils become wet. Care ~hould be taken 10 prevent wetting of the subgrade soils by providing good surface drJinage around the ouli!iide of the building. Footings should be a minimum width of 18 inches for continuous walls and 2 feet for columns. Loose and disturbed soils in footing areas should be removed and the bearing level WRW Log Works October 5, 2016 Page2 extended down to the undisturbed natural soils. The bearing soils should be protected against frost and concrete should not be placed on frozen soils. Exterior footings should be provided with adequate soil cover above their bearing elevations for frost procection . Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupponed length of at least 12 feet. Structural fill placed within floor slab areas can consist of the on-site soils compacted to at least 95% of standard Proctor density at a mo isture content near optimum. Backfill placed around the structure should be compacted and the surface graded to prevent ponding within al least 10 feet of the building. The recommendations submitted in this Jetter are based on our observation of the soils exposed within the exploratory pits and do not include deep subsurface exploration to evaluate the subsurface conditions within the loaded depth of foundation influence. This study is based on the assumption that soils beneath the footings have equal or better suppon than those exposed. The risk of foundation movement may be greater than indicated in this report because of possible variations in the subsurface conditions . In order to reveal the nature and extent of variations in the subsurface conditions below the excavation, drilling would be required. It is possible the data obtained by subsurface exploration could change the recommendations contained in this letter. Our services do not include determining the presence, prevention or possibility of mold or other biological contaminants {MOBC) developing in the future. If the client is concerned about MOBC, then u professional in this special field of practice should be consulted. If you have any questions or need further assistance , please call our office. Sincerely, Louis Eller Reviewed by: LEE/ksw attachments H -P ~KUMAR Project No. 16-7-376 ·-. Moisture Content = 8.6 percent Dry Density ... 87 pcf 0 Sample of: Sandy Silty Clay -~ From: Pit at Southwest Corner at 2 Feet -r--,... ,.. "( } 1 2 --3 ~ -./ ~ v Compression / .._. ~ _ ... --upon 4 wetting 5 ii. c 0 "iii Cl) 6 • ~ \ c. E 0 7 u \ 8 9 10 \ 11 \ 12 \ ' 13 .:\ 14 \ 15 \ ' 16 p 01 10 10 100 APPLIED PRESSURE -kSf 16-7-376 H-P~KUMAR SWELL-CONSOLIDATION TEST RESULTS Figure 1 G-: !..:.:r:tc.rii ~r: :-t~.,..,: re .. "~~ 1f'Wl ~:-:-: P.t.,,:u; •1'\ t.;:::.itr; I \:r\1,:Jf':nt:ti:.. Moisture Content = 14.0 percent Dry Density = 9 1 per ' Sample of: Sandy Silty Clay From : Pit at Southwest Corner al 4 Feet 0 ---i""-.. ~ i 1 !"-.,.... ... r..... r-:'11 2 Compression upon [...----~ v ... '"' wetting ..... 3 ,, ~ ~ t:-i.- 4 I 5 \ \ t;e. c 6 0 \ iii UI (II 0. 7 E 0 (.) 8 ' 9 \ 10 \ \ 11 • 12 \ ' 13 14 \ , 15 01 1.0 10 100 APPLIED PRESSURE • ksf 16-7-376 H-P~KUMAR SWELL-CONSOLIDATION TEST RESULTS Figure 2 Moisture Content = 15.7 percent Dry Density = 94 pcf Sample of: Sandy Silty Clay From: Pit al Northeast Corner al 3 }'2 Feet 0 r---'"'Ii) ~ 1 Compression ~ I< i.-~ g ........ upon 'in ~welting ~ 2 a " ~ I\ u 3 ~ , 4 \ ' 5 \ ' 6 ~ 01 1.0 10 100 APPLIED PRESSURE • ksf 16-7-376 H-P~KUMAR SWELL-CONSOLIDATION TEST RESULTS Figure 3 H-P~KUMAR TABLE1 SUMMARY OF LABORATORY TEST RESULTS Project No. 16-7-376 SAMPLE LOCATION NATURAL NATURAL GRADATION ATTERBERG LIMITS UNCONFINED PERCENT PIT MOISTURE DRY GRAVEL SAND PASSING LIQUID PLASTIC COMPRESSIVE DEPTH CONTENT DENSITY N0.200 LIMIT INDEX STRENGTH SOIL lYPE (%) (•/o) (ft) (%) fncn SIEVE 1%\ 1%\ fPSFl SW 2 8.6 87 Sandy Silty Clay Comer 4 14.0 91 Sandy Silty Clay NW 3 12.8 92 3.000 Sandy Silty Clay Corner I NE 3 1h 15.7 94 92 Sandy Silty Clay Comer