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Home My WebLink AboutSubsoil StudyH-P*KUMAR 5020 Gounty Boad 154 Glenwosd Springs, CO 816t1 Phsne: (970) S45-7988 Fax {970} 945.8454 Email: hpkglenwood@kumarusa.com Geotðchnieål Evlçtineerin$ I gï!gi*€tilfl{] ***l*gy f"{*Ter¡als I¡ã$lin$ I Fnvironm,rnl*f Office Localions: Parker, Glenwood Springs, and Silviarthome, Calorado STJBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE LOT 6, FOUR MILE RANCH RED CLIFF CIRCLE GARFIELD COUNTY, COLORADO PROJECT NO. l6-7-s76 NOVEMBER 28,2016 PREPARED FOR: VILLALOBOS CONSTRUCTION ATTN: MARIO VILLALOBOS 620 WEST PARK STREET MARBLE, COLûRADO 81623 {m, ari os m,¿rblc @ _v-a hoç.c 0m} TABLE OF CONTENTS PURPOSE AND SCOPE OF STUÞY............... ......"."....,...- I - PROPOSED CONSTRUCTTON ....,.....,,....- | - STTE CONDITITNS ,, FIELD EXPLORATICIN - t- -)-S UBSURFACE CONDITICINS ........ FOUND.4,TION BËARINC CONDTTIONS DESIGN RECOMMENÐATIONS ............. FOUND.4TIONS FOUNDATION AND RETAININO V/ALLS FLOOR SLABS....,. UNDERDRAIN SYSTËM.. SURFACE DRAINAGE ...., LTMITATIONS FIGURE I - LOC.A,TTON OF EXPLORATORY BORTNGS FICURE 2 - LOGS OF EXPLORATORY BORI}¡CS FIGURE 3 - LECEND AND NOTES FIGURES 4, 5 AND 6 - SWELL"CCINSOLTDATTON TEST RESULTS TABLE I- SUMMARY OF LABORATORY TËST RESULTS -?_ ....- 3 - 3- 4- -\- ..........".- 6 - ............- 6 - _1- H-P * KUMAR Praiect No, 16.7-576 PURFOSE ANI} SCOPE OF STUDY This report presËnts the results of a subsoil study for a proposed residence to be located at Lot 6, Four Mile Ranch, Red Cliff Circle, Garfîeld County, Colorado. The project site is shown on Figure L The purpose of the study was to develop recommendations for the foundation design. The study was conducted in acccrdance with our proposal for geCItechnical engineering services to Villalobos Construction dated November 8,2016. A field exploration prcgrarn consisting of exploratory borings was conducted to obtain information on the subsurface canditions. Samples of the subsoils obtained durin¡¡ the field exploration were tested in the laboratory to determine their classification, compre$sibility or swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendation.ç for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during this study and presents our conclusions, design recommendations and other geotechnical engineeringconsiderations based on the proposed construction and the subsurfaee conditions encountered. PRTPOSET} CONSTRUCTION The proposed residence will be one and two story wood frame construction above a basement and with an üttåched gârage located in the building enve lope shown on Ëigure I. ISasement and garage flsors will be slab-on-grade. Grading for the struçture is assumed to be rel¡¡tively minor with cut depths between about 3 to I feet. l#e assume relatively light foundation loadings, typical of the proposed type cf construction. If building loadings, location or grading plans change significantly from those dsscribed above, we should be notifìed to re-evâlu¡¡te the recommendations contained in this report. H-P$ KUMAR Prerject No. 1fi-7-57ô -2- SITE CONDITTONS The vacant lot is vegetated with grass and weeds. The ground surface slopes gently down to the west. An irrigation ea*rement is located downhill of the building envelope in the rear of the lot. FIELD EXPLOR.4.TION The field exploration for the project was conducted on November 14,2016. Two exploratory borings were drilled at the locations shown on Figure I to evaluate the subsurface conditions. The borings were advanced with 4 inch diameter rontinuous flight augers powered by a truck- mounted CME-458 drill rig. The borings were logged by a representative of H-P/Kumar. Sarnples of the subsoils were taken with l% inch and 2 inch LD. spoon samplers. The sarnplers were driven into the subsoils at various depths with blows from a 140 pound hamrner falling 30 inches. This test is similar to the standard penetration test described by ASTM M¡xhod D-l jg6. The penetratisn resistance values are an indication of the relative density or cÐnsistency of rhe subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Figure 2. The samples were returned {c our laboratory for review by the project engineer and testing. SUBSURFÅCE CTNT}ITTûNS Graphic logs of the subsurface conditians encounterÊd at the site are shown an Figure 2. The subsoils below about one foot of tcpsoil eonsist of very stiff sandy silty clay to about ? feet in depth overlying basalt cobbles ancl boulders in a silty sand matrix. Drilling in rhe coarse granular soils with auger equipment was difficult due to the cobbies and boulders and drilling refusal was encountered in the depasit. Laboratory testing performed on samples obtained from the borings consisted of natural moi.çture content and swell'consolidation. Results of swell-consolidation testing performed on relatively undisturbed drive samples of the clay soils, presented an Figures 4, 5 and 6, indicate low H.P * KUMAR Project No. 16-7-576 -3- compressibility under light loading and variable low collapse or expansion when rvetred. The laboratory testing is summarized in Table L No free water wås encüuntered in the borings at the time of drilling and the subsoils were slightly moist. FOUNÐATION BEARTNG CONÐTTIÛNS The residence as planned will be above a basement level and the underlying basalt cobbles and boulders in a sandy silty matrix should be exposed in the excavation base. The attached gârage excavation will likely expose the upper clay soils. The upper clay soils have variable settlemcnUheave potential when wetted that could result in post-eCInstruction building movement or distress. Care should be taken in the surface and subsurface drainage around the house to prevent the bearing soils from becoming wel It will be critical to the long term performance of the structure ùåt the recommendations for surface grading and subsurface drainage contained in this report be followed. The amourt of settlement, if the bearing soils become wet, will mainly be related tt the depth and extent of subsurfare wetting of the clay soils. Extendinig the garage foundation down to the granular soils or replacing the clay with compacted structural fill should provide a lower risk of differential rnovement and distress. DßSIGN RECOMMENDATIONS FOUNDATTÛNS Considering the subsurface conditions encountÊred in the exploratory borings ancl the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural granular soils or compacted structural fîll. The design and construction criteria presented below should be observed for a spread footing faundation syst€m. H-P q È{UMAR Prajecl No. 16.7-576 4 r)Footings placed CIn the undisturbed natural granular soils or compacted structural fìll should be designed for an altowable bearing pressure of 2,000 psf. Based on experience, we expect $ettlement of footings designed and constructed as discussed in this section will be about I inch or less. The footings should have a minimum width of l6 inches for continuous walls and 2 feet for isolated pads. Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement af laundations at least 36 inches below exterior grade is typically used in this ârea. Continuous foundation walls should be reinforced top and bottom tc span local anomalies such as by assuming än unsupported length sf at least l? feet" Foundation walls acting as retaining structurcs should also be designed to resist lateral eårth pressures as discussed in the "Foundation and Retaining wail$" section of this rcport. The topsoil, clay soils and any loose or disturbeel soils should be renroved and the footing bearing levcl extended down to the undisturbed natural grâ\¡el and cobble soils' The exposed soils in footing area should then be moistened ancl compacted. Structur¿¡l fill should be a granular soil such as road base compactecl to at le¿r-st 98Tr ol standard Procmr den.sity. A representative of the geotechnical engineer should observe all footing excavations priûr to concretË placement to evaluate bearing conditir:ns. 3) 4l 5) 6) FTUNDATION AND RËTATNINC WALLS Foundation walls and retaining structures which are laterally supported and can be expectecl to undergo only a slight amount of deflection should be designed for a lateral earth pressure compuled on the basis of an equivalent fluid unit we ight of at leasr 55 pcf for backfill consisting of the on-site soils. Cantilevered retaining structures (if any) which Bre sepârate fr6m rhe residence and can be expected to deflect sufficiently to mobilize the full åctive earth pressure condition should be elesigned for a lateral earth pres$ure computed on the basis of nn equivalent fluid unit weight of at least 50 pcf for backfîll consisting of rhe on-sire soils. 2) H-P * KUMAR Project No. 16-7.576 -5- All fbundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressure$ such as adjacent footings, traffic, construction m¿lterials and equipment. The pressures recomrnended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the lateral Fressure imposed on a foundation rvall or retaining structure. l\n underdrain should be provided lo prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lifts and compacted to at least gt%o cf the maximum standard Proctor density at a moisture content slightly above optimum. Backfill placed in pavernent and walkway rireffi should be compacted to at leastgSTo of the maximurn standard Proctor density. Care should be taken nat to overcompârt the backfill or use large equipment near the wall, since this could cause sxcôssive lateral pressure an the wall. Some settlement of deep foundation wall backfïll should be expected, even if the material is placed correctly, ând could result in distress to facilities eonstrucred on the backfill. The lateral resisfance of foundatisn or retaining wall fcotings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of thc footings can be r:atculated based on a coefficient of friction of 0.45. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 35û pcf. The coefficient of friction and passive pressure value.s recommended above ¡¡ssume ultimate so¡¡ strength. Suit¿ble factors of safety shsuld be included in the design ro limit the srrain which wi¡ occur Írt the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should compacted to at least g57o of the maximum standard Proctor density at a moisture slightly above optimum. FLOOR SLABS Lightly loaded slabon*grade construction placed on the clay soils will have a risk r¡f movement and distress. TVe recommend at least 2 feet of granular soil such as ro*el base be placed below slabs in clay soils areas. To reduce the effects of some differential movemenl, floar slabs should be separated from ¿rll bearing walls and columns with expansion joints which allow unrestrainecl H-P s KUMAR Pro,jecl No. '16.7-576 -ó- vÊftical movemsnt. Floor slab control joints should be used to reduce damage du* to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be established hy the designer based on experience and the intended slab use. ^À minimum 4 inch layer of free- draining gravel should be placed beneath b¿sement level slabs to facilitate drainag,e. This material should consist of minus 2 inch aggregâte with at least 5û7o retained oû tho No. 4 sieve and less than 2Va passing the No. 200 sieve. All fill materials for suppart of floor slabs should be compacted to at leasr g57o of maximum standard Proctor density at a moisture content near optimum. Required fîll should consist *f granular soils devoid of vegetation, topsoil and oversized rock. UNDERDRAIN SYSTEM Although free rvater was not encountered during our exploration, it has been our experience in the area that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched csndition. \rye recornmend belaw-grade constructicn, $uch as retaining walls, crawlspace and basement areast 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 backfïll surounded above the invert level with free-draining granular mflterial. The drain should be ptaced at each level of excavrtion and at least I foot below lowest adjacent linish grade and sloped at a rninimu m lVa to a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than 2fi passing the No. 20û sieve, le.çs than 507c passing the No. 4 sieve and have a maximurn size of 2 inches. The drrin gravel baskfill should be at least l¡l: feet deep. SURFACE DRATNAGE The folbwing drainage precautions should be observed during construction and maintained at alt times after the residence has been completed: l) Inundation ofthe foundation excavatiûns and underslab areas should be avoided during constructicn, H-P * KUMAR Pr{'ject N*. 1S-þSTS -7- 3) Exterior backfill should be adjusted tû near optimum moisfure and compacted to at least 95Vo sf the maximum standard Proctor density in pavement. and slab areas and to at least 907o of the maximum standard Proctor density in landscape âreas" The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. we recommend a minimum slope cf l? inches in the first 10 feet in unpaved areas and a minimum slope of 3 inches in the fîrst l0 feet in paved areas. Free-draining wall backfill should be covered with filter fabric and capped with about 2 feet of the an-sire ctay soils ro reduce surface wûter infiltration. Roof downspouts and drains should discharge well beyond the limirs of all backfill. Landscaping which requires regular heavy inigation should be located at least l0 feet from foundation walls. Consideration should be given to use of xeriscape to reduce the potenfial for wetting of soils below the building caused by irrigation. 4) !.IMIT.{TIONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this areÍì ¿!t this time. We make no warränty either express or implied. The conclusions and recommendations submitted in this report are based upon the clâta obt¿¡ined from the exploratory borings drilled at the locations indicated on Figure l, the proposed type of construction and our experience in the area. Our services do not include determining ths presence, pr€ventiCIn or possibility ol mold or other biological contaminant$ (MO[]C) developing in the future. If the client is concerned about MOBC, then a profe.ssional in this spccinl field of pr¿rctice should be consulted. Our findings include interpolation ancl extrapolation of rhe sub.curface conditions identilied a[ the explorafory borings and variations in the subsurface conditions rnay not become evident until excavation is performed. [f cçnditions encountered during construction appear different from those described in this report, we should be notifiect so that re-evaluation of the recammendatirns may be made" 2, s) H-Pe KUMAR Projecl N*. 16"7-575 -8- This report has been prepared for the exclusive use by our client for design purpories. Vy'e 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 and mcnitor the implementâtion of our recommendâtions, and to verify that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. Vy'e recommend on-sife observarion of excavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Subm¡tted, H.P* KUMAR Louis Eller Reviewed by: Steven L. Pawlak, P LEË/ksw H-F q KUMÅß Proinct Ns. 1S-T-576 c<ra LOT 5 1 / LOT 7 LOT6 %t+ offi APPROXIi¡|ATE SCALE.F€EÎ a ENVELOPE BUILDING BORING 2I 1 6-7*578 H-PryKUMAR LOCATION OF EXPLORÅTORY AOAINçS Fis. T t , aI!¡ BI'RING 1 EL. r00' BORINC 2€1. t00' 0 o 25/12 WC=6,5 Ðtlal I I 23/t2 WC=6.2 00=107 5 ze/12 WC=6.7 ODg1O5 Ê 3t/12 :r o-t Ë, t0 50/3 10 15 15 I 6-7-576 H.PryKUMAR LOGS CIF EXPLORATORY BORING:!Fís. 2 LEGEND T0PSO|L; ORGANIC SÂNDY SILT AND CLAY, FIRM, MtlST, 0ÀñK BROWN. CLÀY (CL)¡ SANDY, SILTY, VERY STlrF, SLIGHTLY MtlST, gRoWN, SLI0HTLY CÂLCÂR€OUS, LOW TO UEDTUM PtÂsTtClW. ÊASALT 6ü88LeS ÂNO BOULDIRS (cM)¡ rN A SlLfi SAND MATRIX, DENSE, SLIûHTLY MolST, MIXEO BROWN. ßELATIVELY UNDISTURBEO ORIVE SAMFLEI Z-INCH l.D. CALIFOñN|A Lll'¡ËR SAMPLE. oRtvE SAMFLE; STANDÀRD PENETRATIOH TESÎ (SPT), I 5/S |NCH 1.0. SpLtT spûON SAMPLE, ASTM D-t5A6. '¡q7¡1 ORIVE SAMFLE BLOW COUNT. INÍIICATES THAT 25 ELOWS OF A 14S-PúUNû HAMh{ER--l'- TÅLLING ¡O INCHTS WERË RESUIRET TO TRIVE THE CAUTORNIÂ OR SPT sÀMPLEIT f 2 INCHT5. PRACTICAL AU6EÊ R€FUsåL. WI{ERS SHOWH ASOVË BOTTOM OF BORING, INDICATES THÂT MULTIPLE ATTEMPTS WHEfiE MAOE TO ÅDVANCE THE TIÛL[. N,OTES I. THË ËXFLORATORY BORINCS 1IIERE ORITLEO ON NÛVEMBËR I4,2Û16 WITH A 4-INCH OIÂMITER CONTINUTUS FLIGHT POWER AUGËR. 2. THE LOCÂTIONs OF THE EXPLORATORY BORINGS WESE MEÂSUREO AFFROXIMÂTÊLY 8Y PACII-IG FROM FEATURE5 5HOWN ON THE SITE PLÂH PROVIOEO. 3. ÏHE ELËVATIONS OT THE EXPLTRATORY EORINGS WERE MEASUREO BY HANO LEVEL ANO FEFER TO BÛRING 1 A5 lOO FEEI, ÂSSUMEO. THE LOGS OF THE EXPLORATORY BORINGS ÂRË PLOTTEO TO OEFTH. 4. THE EXPLORAÏORY ÊOßING LOCATIONS AND ËLEVÅTIONS SI{OULÍ} BE CONSIDEREO AOCURATE O¡ILY TO THE DE6REË I}IIFLIEÐ EY TI{E METHOO US€D. 5. THË LINES BETWEEN MATERIÂLS SHTWF¡ ON THI TXPLORATORY BORING LOGS NEPRTSENT THE ÀPPROXIMATI €OUNOARIES BETWEEN MÅTERIAL TYPES ANT TH€ TRANSITION5 MÀY gË TRÂDUAL. 6. GROUNOWÅTER WAs NOT ENCOUNTEREO IN THE HÊfiINGs AT THE TIMË OT ORILLI¡IG. 7. I.ô8ORATORY ÍEST RESULTS;lrc = WÀTER CoHTENT (X) (A5TM t 22161t0D * 0Rr pENStly (pcf) (A$Ti,t Ð 2?t6)¡ ñ n w þ i t 1 6-7-576 H-PryKUMAR LEGËND ANI} NOTES Fig. 3 SÅ¡rlPLE 0F: Sondy Sllly Cloy FROM:Borlng 1 e 2.5' WC = 6.5 %, tt = 111 pgf , 0N j-l l¡¡3 an J-z zIP Ël ow o<J -4 1 6-7-576 H-PæKUIVIAR SWELL-CONSOLIDATION TEST RT5ULT Fig. 4 SÀMPLE 0F; Sondy Sllly Cloy FROH:Borlng 1 g 5' l,VC = 6.7 ,1, Dt = 105 pcf h cl h AOÐITIO'{AL CC}MPRESSION UN0ER CONSTAI.IT PRESSURË DUE TO WETTING I o a-1 }E JâJ -¿.l¡,Fvt ¡_3 otr $*+o UIz.() 'J -5 -6 -7 16-7-376 H-PryKUMAR SWTLL-CONSCILITATION TTST RESULT Fig. 5 åI SAMPLE OF: Sondy Sllty Ctoy FROM;BorlngZA?.5' WC = 6.2 %, DÐ = IOZ pcf h EXPANSIO¡I UNDER CONSTANT PRESSURE UPON WËTTINC 2 0x j-l t¡J3an t_2 g Õ ö lt1zö(J_4 t.0 100 ,,16-7-576 H.PTICJIVIAR STVTLL-CONSOLIDATION TTST RESULT Fis. 6 H-P*lruMARTABLE 1SUMMARY OF LABORATORY TEST RHSULTSProjectNo. 16.?-576SOIL TYPESandy Silty ClaySandy Silty ClaySandy Silty ClayUNSCNFINçDcolrtPREs$tvE$TRËNCTHATTEÊBERG L¡MITSF¡..âSTIı¡NDEXt%lLIQI.'IDLlfr,l¡T{?olPÊRÕEMTFASSINGHO.20ûslEt/ESANN{%}GRAVEL(wNATURAL$rittSTtjÊEçSiITENTNATUÊALfIRYÞÊNSITYtllr05tt?6"36.?6.2c*ïeNDEPTH2t/25TrhBOñ!l'¡GI2