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Home My WebLink AboutSoils Report 01.24.2018H.PVKUMAR 5020 County Road 154 Glenwood Springs, CO 81ô01 Phone: (970) 945-7988 Fax (970) 945-8454 Email : hpkglenwood@kumarusa.com Geotechnical Engineering I Engineering Geology Materials Testing I Environmental Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado January 24,2018 Steven I(oski 306 Rabbit Road Carbonclale, Colorado 81 623 steven @ tomroachfl oors.com Project No.17-7-842 Subject:Subsoil Study for Foundation Design, Proposed Residence, Lol7, Stirling Ranch, 405 Skipper Drive, Missouri Heights, Garfield County, Colorado Dear Steven: As requested, H-P/Kumar performed a subsoil study for design of foundations at the subject site. The stucly was conducted in accordance with our agreement for geotechnical engineering services to you dated November 29,2011. The data obtained and our recommendations based on the proposed constrnction and subsulface conditions encountered are presented in this report. Proposed Construction: Design plans were pleliminary at the time of our stuciy. The proposecl 4,000 sqllare foot residence will be 1 and 2 story wood frame construction over a crawlspace or basement located on the site as shown on Figure 1. Cut depths are expected to range between about 2 to 8 feet. Founclation loadings for this type of construction are assulned to be relatively light and typical of the proposed type of construction. If building conditions or foundation loadings are significantly differeut from those described above, we should be notifiecl to re-evahrate the recornmenclations presented in this report. Site Conditions: The lot was vacant with a gravel driveway and water line into the site. The lot slopes gently to moderately down to the east with grades of 2 to 10 percent. South of the building area, the lot slopes steeply down to the south. Vegetation at the site consists of pinon and juniper trees with sparse grass and weeds. Scattered basalt cobbles and boulders wers observed on the ground surface. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The subsoils encountered, below about l to lVz feet of topsoil, consist of basalt gravel, cobbles and boulders in a calcareous sandy silt matrix down to the maximum depth a-L- explored, \Vz feet. Results of swell-consolidation tcsting pcrfonned on a relatively undisturbed sample of the sandy silt matrix soils, presented on Figure 3, indicate low comptessibility under existing low moisture conditions and light loading and a moderate collapse potential (settlement under constant load) when wetted. Results of graclation analyses performed on samples of the basalt rock soils (minus lVz and 5 inch fraction) obtained from the site are presented on Figure 4. The laboratory testing is summarized on Table 1. No free water was observed in the pits at the time of excavation and the soils were slightly moist to moist. Foundation Recommendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, we recomlnend spread footings placed on the undisturbed natural basalt rock soil designed for an allowable soil bearing pressure of 2,000 psf for support of the ploposed residence. The matrix soils tend to compress after wetting and there could be some post-construction foundation settlement. Footings shoulcl be a minimum width of 16 inches for continuous walls and2 feet for columns. The topsoil and loose disturbed soils encountered at the foundation bearing level within the excavation should be removed and the footing bearing level extended down to the untlistulbed nal"ural soils. Ht-rles below footing grade caused by basalt boulder removal should be backfilled with concrete or imported 3/c-inchroad base compacted to at least 987o of the maximum standard Proctor density. Exterior footings should be provided with adequate cover above their bearing elevations fol frost protection. Placement of footings at least 36 inches below the exterior grade is typically used in this area. Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an Llnsupported length of at least 14 feet. Foundation walls acting as retaining strltctures should be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 50 pcf for the on-site soil as backfill, excluding rock larger than about 6 inches. Floor Slabs: The natural on-site soils, exclnsive of topsoil, are suitable to support lightly loaded slab-on-grade construction. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A minimum 4 inch layer of free-draining gravel should be placed beneath basement level slabs to facilitate drainage. This material shoulcl consist of minus ?. inch aggregate with less fhan 507o passing the No. 4 sieve and less than 2o/o passing the No. 200 sieve. H-P!KUMAR Project No.17-7-842 -3 - All fill materials for support of floor slabs should be compacted to at least 95Vo of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site soils or a suitable imported granular material such as 3/q-inch road base devoid of vegetation, topsoil and oversized rock. Underdrain System: Although free water was not encountered during our exploration, it has been our experience that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spling runoffcan also create a perched condition. We recommend below-grade construction, such as retaining walls, deep crawlspace (greater than 4 feet) and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free-draining granular matelial. The drain should be placed at each level of excavation and at least I foot below lowest adjacent finish grade and sloped at a minimum IVo to a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than 27o passing the No. 200 sieve, less than 507o passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least lVzfeet deep. Surface Drainage: The following clrainage precautions should be observed during construction and maintained at all times after the residence has been completed: 1) Inundation ofthe foundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 957o of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum standard Proctor density in lanciscape areas. Free-clraining wall backfill shoulcl be cappecl with about 2 feet of the on-site, finer graded soils to reduce surface water infiltration. 3) The gror.rnd surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. W'e recommend a minimum slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in pavement and walkway areas. 4) Roof downspouts ancl drains should discharge well beyond the limits of all backfill. Graded swales should have a minimum slope of 37o. Limitations: This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area at this time. 'We make no waranty either H-PÈKUIVIAR Project No.17-7-842 -4- express or implied. The conclusions ancl recommendations submitted in this report are basecl upon the data obtained from the exploratory pits excavated at the locations indicated on Figure 1 and to the depths shown on Figure 2, the proposed type of construction, and our experience in the area. 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 abont MOBC, then a professional in this special field of practice should be consulted. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory pits and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appear different from those described in this report, we should be notified at once so re-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for design pulposes. We are not responsible for technical interpretations by others of our information. As the project evolves, we should provide continued consultation and field services during construction to review ancl monitclr the irnplerrentation of our recommettdations, aud to verify that the recolunenclations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommend on-site observation of excavations and foundation bearing strata ancl testing of structural fill by a representative of the geotechnical engineer. If you have any questions or if we may be of further assistance, please let us know Respectfully Submitted, H.P+ KUMAR Daniel E. Hardin, P Reviewed by: SLP DEFVkac attachments Figure I - Location of Exploratory Pits Figure 2 - Logs of Exploratory Pits Figure 3 - Swell-Consolidation Test Results Figure 4 - Gradation Test Results 1'able 1 - Summary of Laboratory Test Results cc JessPeclersen@ H-PèKUMAR Project No.17-7-842 t I i'j, "( \l ,ì'!rii¡. i' :î-j-'a'.- , Iq,Í<<r ' / I1 ir'I .-,Hlru \ t?l,!<-: r ''J-ì*>t" ì 405 SKIPPER DRIVE Ptf ffiÞ I I .-ì{r,it:l-l ¿ ,' T.Ì:..kr' .\,r .- 'i+\:: 'j'r i' ì ---.i ì I j,ìr,É.i 1.""..i,i ( { /, ,t I I I BUILDING ENVELOPE \î I I 2\T .t I \ ì. ,/ PIT I f, 1 /:v "7 s;# l'+'E 'ixfi' l'. o20 SCALE _ FE ET /'- _i \j i'-!'\ \ .'t 20 I 17 -7 -842 H-PryKUMAR LOCATION OF EXPLORATORY PITS Fig. 1 I o PIT .I EL.7111' Pn2 EL. 71 05' 0 0 F- L¡l Ld L! I-|-(L tdô -11+4=23 -r -200= i 6 WC=8.0 DD=79 È- TJ tJJL I-FL TJo 5 5 I + 4=43 -200= 1 6 10 10 LEGEND TOPSOIL; ORGANIC SILT AND CLAY, SANDY, FIRM, MOIST, DARK BROWN BASALT GRAVEL COBBLES AND BOULDERS (GM) IN SANDY SILT MATRIX, DENSE, SLIGHTLY MOIST, BROWNISH WHITE, CALCAREOUS. F HAND DRIVEN 2_INCH DIAMETER LINER SAMPLE. -l I I _t DISÏURBED BULK SAMPLE. NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A JOHN DEERE sOG BACKHOE ON DECEMBER 8, 2017. 2. THI LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED, 3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE OBTAINED BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN PROVIDED. 4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5, IHE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESÊ,N]'IHË APPROXIMATE BOUNDARIES BEÏWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF DIGGING. PITS WERE BACKFILLED SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSTTY (pct) (aSrU D 2216); +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ISTU O AZZ); -2oo = PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1 1 40) 17 -7 -842 H-PVKUMAR LOGS OF EXPLORATORY PITS Fig, 2 à 1 0 -1 N JJLI =Ø I zotr o Jolnzo(J -2 -3 -4 -5 -6 -7 -8 -9 -10 t.0 APPLIED PRESSURE - KSF IO SAMPLE OFI Calcoreous Sondy Silf Molrix FROM:Pit2@5.5' WC = 8.0 %, Dù = 79 pcl ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING I I I I l l hm ldt rdultr oppry onlr lo lh. ¡oñpl6 lfild. Th. ldl¡ñg rapô.t lholl nol b. r.producld, .tcêpt ¡ñ tull, rìthôst lh. rr¡ll.n ôpprôvôl ol Kumor ond Aræhld. lnc. Sr.ll Cor.oÍdolioñ tâ¡lìng Fdomôd in ûccô.doñc. rith ßrU D-496. 17 -7 -842 H-PryKUMAR SWELL-CONSOLIDATION TEST RESULTS Fig. 3 !J z t00 90 ao 60 50 10 JO 20 to o fo 20 JO 40 50 60 70 lo ¡o too = Ê E 1,.125 2.O DIAMETER OF PARTICLES IN MILLIMETERS rs2 CLÁY TO SILT COBBLES GRAVEL 23 % SAND 6T % LIOUID LIMIÏ PLASTICIÍY INDEX SAMPLE OF: Colcoreous Silþ Sond wllh Grovel SILT AND CLAY 16 % FROM:Pit1O3'-4' 2 * P È r00 90 80 7â 60 50 40 JO 20 to o o lo 20 50 ¡0 50 30 70 t0 s0 r00 z c .oo2 ,ol9 .037 t9 2.O IN MILLIMETERS 152 CLAY TO SILT COBBLES GRAVEL 43 '( SAND 41 7T SILT ANO CLAY LIOUID LIMIT PLASÎICIIY INDEX SAMPLE 0F: Colcoreous S¡lly Sond ond Groval FROM: Pil 2 O 6'-6,5' 16 I Ìh.t. l.rl r.rulb opply only to th.!oñpl.! whlch w.r. l.!hd. Thrl.¡llñg r.porl rholl not b. roproduccd,.xc.pl ln lull, wllhoul lh. wrlil.ñ opprovol of l(umor t AE¡oc¡oh¡, lnc.Sl.v. onoly¡¡¡ l.sflng ¡. Þ.rfom.d ln occordoncr wlth ASTM 0,t22, ASTI¡ Cf36ond/or ASIM Dll¡10. HYDROMETER ANALYSIS SIEVÉ ANALYSIS T¡UE RADITGS 24 HnS 7 HRS U,S, STANOARO SÊRIES CLUR SOUARE OPENINCS t/A" \t^ô t tltr - --- I :.,---¡:::::r _-. ,_l---- 1::::T: _1;*:.t-.-t-. .._, .:.i. .--=r- "-* =::::t SAND GRAVEL FINE MEDIUM ICOARSE FINE COARSE HYDRÓMEfER ANÂLYSIS SIEVE ANALYSIS ilYE RADINGS 24 HRS 7 HRS u.s. slANoARo sERrEs CgR SOUARE OPENIXCS t/A" 3lt' 1 t/t- t1, I -,] ¡/--. ¡11 .. I--,f -- ....-1 .,..:- -,-,..,t-. - - 1,;/- /I I ----}.---.-_.{----*- GRAVELSAND FINE MEDIUM FINE COARSE 17 -7 -842 H-PryKUMAR GRADATION TEST RESULTS Fig. 4 H,P*KUMARTABLE 1SUMMARY OF LABORATORY TEST RESULTSProject No.17-7-842SOILTYPET6Calcareous Silty Sand withGravelCalcareous Sandy SiltMatrixCalcareous Silty Sand andGravelUNCONFINEDCOMPRESSIVESTRENGTH(PSF)ATTERBERG LIMITSPLASTICINDEX(%\LIQUIDLIMIT(%lPERCENTPASSINGNO.200SIEVE16GRADATIONSAND%l6t4TGRAVEL(%)2343NATURALDRYDENSITYlocfl79NATURALMOISTURECONTENT(%l8.0SAMPLE LOCATIONDEPTHlfil3-43V26-6VzPIT12