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Home My WebLink AboutSubsoil Study for Foundation Design 04.21.2017H.PVKUMAR Geotechnlcal Engineering I Englneering Geology Materials Testing I Environmenùal 5û2ö tounly Road 1Sl Glenwood Springs, CO 81601 Phone: (970) 945-7988 Fax (970) 945.8454 Email: hpkglenwood@kumarusa.com Office Locations: Parker, Glenwood Springs, and Summit County, Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE 6350 COTTNTY ROAD 2I.¡f GARFIELD COUNTY, COLORADO pROJECT NO. 17-7-245 APRIL 2t,2017 PREPARED FOR¡ FIONA LLOYI} Â**rå r-a.Fuiïr I S(}¡tlt ¿ú, SILT, COLORADO 81652 ifionatloyAZOt+Os TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION ......... SITE CONDITIONS FMLD EXPLORATION ........... SUBSURFACE CONDITIONS ......... FOUNDATION BEARING CONDITIONS ... ÞESIGN RECOMMENDATIONS FOI.JNDATIONS ."....... FLOOR SLABS...... ST]RF'ACE DRAINAGE LIMITATrONS...,.........,.... FIGURE I - LOCATION OF EXPLORATORY BORING FIGURE 2 - LOG OF EXPI,ORATORY BORTN{i FIGURES 3 through 5 - SWELL-CONSOLIDATION TEST RESULTS TABLE I- SUMMARY OF LABORATORY TEST RESULTS I I _,, _ -') - -3- -^- -a- 5- ^ñ- -7- H-PèKUMAR Elr^lâôr il^ {? ? 4lç PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located at 6350 County Road 214, Garfield County, Colorado. The project site is shown on Figure I. The purpose of the study was to develop recommendations for foundation design. The study was conducted in accordance with ortr agreement for geotechnical engineering services to Fiona Lloyd, dated March 20,2017. A field exploration program consisting of an exploratory boring was conducted to obtain information on the subsurface conditions. Samples of the subsoils obtained during the field exptûfaüon were tested ln the laboratory to determine their classification, compressibility or swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during ttus $ttlðy äno Frese.nts our conclusronsr resoflrmendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION ê e¡¡¡B¡ü sru¡J w\jur¡ .rra¡ür¿ ¡rtrùüil.}¡s ¡uLateti û* t*e FTüÌËf{y äï $l¡{ññ¿n Ðü Figure 1. The floor is planned to be slab-on-grade. We assume excavation for the building will have cut depths of from about 2 to 4 feet. For the purpose of our analysis, foundation loadings for the structure were assumed to be relatively light and typical of the proposed type of *ui:¡'1-Ê UÐtÈÚtl. If building loadings, location or grading plans are significantly different from those described above, we should be notified to re-evaluate the recommendations contained in this report, H.PtKUÍVIAR Project No. 17-7-245 -2- SITE CONDITIONS The site is located in an existing agricultural field on the south side of County Raad ?14 fFeach Valley Road) across from the New Castle Gardens commercial property. The ground surface, which appears mostly natural, is relatively flat with a strong slope down to the southwest. Vegetation consists of grass and weeds. The V/are and Hines ditch borders the property along the south side. FIELD EXPLORATION The field exploration for the project was conducted on March 37,2017. One exploratory boring was drilled at the location shown on Figure I to evaluate the general eubsurface conditions. The approximate corners of the proposed builcling were field staked by the client prior to our field exploration. The boring was advanced with 4 inch diameter continuous flight auger powered by â trtlck-mounted CME-458 drill rig. The boring was lugged by a representative of H-p/Kumar. vs¡¡rP¡r,tulr¡lLrl¡t/ùu¡¡¡tw{;¡ül¡trtttiwrrrrd¿lttçtir.¡J.¡tpuu¡¡sAnlplgf. fogSamplgfWASOflvgn into thc subsoils at various depths with blows from a 140 pound hammer falling 30 inehes. This test is similar to the standa¡'d penetration test described by ASTM Method D-15g6. The penetration resistance values âre an indication of the relative density or consistency of the subsoils' Depths at which the samples were taken and the penetration resistance values are shCIwn CIn the Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. S UITSURJ'ACE CONDITIONS A graphic log of the subsurface profile encountered at the site is shown on Figure 2. The subsoils encountered, below about 7r foot of organic topsoil, consisted of stiff, sandy tcl very sandy silty clay underlain at a depth of about 672 feet by very stiff to hard, sandy clay. The upper sarrcly silty clay soils contained scattered gravel and cobbles increasing with depth. H-PtKUIVIAR -3- Laboratary testing performed on samples obtained during the field exploration included natural moisture cûntent and density, and percent finer then sand size gradation analysis. Swell- eonsolidation testing was performed on relatively undisturbed drive samples of the subsoils. The swell-consolidation test results, presented on Figures 3 through 5, indicate low compressibility ut¡uðr lçlãrrvsly ltgnr $urcnarge toaülng and a lcw to moderatË expanslon pûtential when wetted under a constant light surcharge. The testing indicated swelling pressures in the range of about 5,000 to 15,000 psf with the higher swelling pressures in the underlying sandy clay soils. The laboratory testing is summarized in Table l. ¡!þ a{ùv +çùÈ*i lyaè eiÁi'$¡¡i¡rereu ¡¡r rus uurrt'tË, ãì. trillg ûl üff¡ifng Af¡ú Íne SUbSOIIS Wefe Slightìy moist. F'OUNDATTON BEARING CONDITIONS The subsoils encountered at the site possess low to moderate expansion potential when wetted. Spread footings may be feasible for support of the residence with the understanding of a risk of bttilding movement and distress if the clay bearing soiis were to become wetted. 'fhe amount of rütvement Êr heave wtll mainly be related to the depth and extent of subsurface wetting. Surface runoff, Iandscape irrigation, and utility leakage are possible sources of water which could cause wetting. It will be critical to the long term performance of the structure that the recommendations for surface drainage contained in this report be followed. Fcr a spread footing foundation, the expansion potentìal of the clay soils can probably be mitigated by load concentration to reduce or prevent swelling in the event of wetting below the foundation bearing level, The building will be relatively light and load concentratic¡n would likely require pad and grade beam construction to concentrate loads, Another option for a spread footing f'oundation is subexcavation of a deprh (typically 3 to 4 feet) of the soils and replacement with importecl structural fill. A relatively iow risk of movement foundation system would be helical piers, screw piles or drilled piers based in the clay soils below an assumed wettecl depth, estimated at about Z0 feet at H.P*KUMAR Project No. 17-7.245 -4- this site. Provided below are recommendations for a spread footing foundation system assuming some risk qf foundatisn movËmsnt is ar:r:egtable. If recommendations for a oier crsiir foundation are desired, we should be contacted DESIGN RECOMMENDATIONS FOUNDATIONS Considering the stlbsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we believe the building can be founded with spread fcrti*gr staæd on undisturbed natnral soils with a minimum dead load or on a minimum 3 feet of proper.ly placed and compacted road base without a minimum dead load, with some risk of movement and distress. The road base can consist of CDOT Class 2, 5 or 6 aggregate base course, or other similar material as approved by us. Precautions shsuld be taken to arevent wetting af rhe clav bearing soils. The design and construction criteria presented below should be observed for a spread footing ioundation svsts$1. I ) Footings placed on the undisturbed natural soils can be designed for an allowable bearing pressure of 3,000 psf. The footings should also be designed fbr a minimum dead load pressure of 1,000 psf. In order to satisfy the minimum dead Ioad pressnre under lightly loaded areas, it may be necå$sary to conceiltrãte Isads by using a grade beam and pad system. Wall-on-grade construction is not recommended at this site to achieve the minimum dead load, 2) Footings placed on a minimum 3 feet of compacted structural fitl can be designed for an allowable soil bearing Fressure of 2,000 psf. The structural fill shouid be compacted to at lcast g8Øa standard Proctor density at a moisture content within ZVo of optimum' The structural fill should extend at least 2 feet beyond the edges of the foorings. 3) Based on experience, we expect initial settlement of footings designed and construeted as discussed in this section will be I inch or less. There could be H-PIKUMAR '¡:r5i--*¡ rl4 t- ? *-i- -5- 4) additional movement (heave) if the clay bearing soils were to become \ryetted. The magnitude of the additional movement would depend on the depth and extent of the wetting but may be on the order of vzta lvz inches. We should firrther evaluate the expansion potential of the soils at the time of construction. The footings should have a minimum width of l6 inches for continuous footings and24 inches for isolated pads. Continuous foundation walls should be heavily reinforced top and bottom to span local anomalies and better withstand the effects of some differential movement such as assuming an unsupported length of at least i5 feet. Foundation walls acting as rttaining srructures should also be designed to a lateral earth pressure corresponding to an equivalent fluid unit weight of at least 55 pcf. Exterior footings and footings beneath unheated areas should be provided with adequate soil cover above their bearing elevation for frost protection. Placement of foundations at least 36 inches below the exterior grade is typically used in rhis afea. Prior to the footing construction, all topsoil, the required depth of subexcavation as needed and any loose disturbed soils should be removed and the subgrade mclçt*aed ta near optim¡Irn and ccmpacted. A representative ofthe geotechnical engineer should observe all footing excavations and test structural fill compaction on a regular basis prior to concr€te placement to evaluate bearing conditions. 8) }.LUUR SLAT'¡i The on-site clay soils possess an expansion potential and siab heave could occur ifthe subgrade soils were to become wet. Slab-on-grade construction may be used provided precautions are rilÀüu lu ôlr¡¡rr ljulsttrla¡ frluvernËfit ang tne r$K of olsrress to tne Þutldlng rs aecepted by the owner. We recommend a minimum 3 feet of compacted road base as structural fill be provided below the slabs to reduce the risk of floor slab movement. The road base will not eliminate the risk of floor slab movement and distress, especially if the underlying clay soils were to become vreûet ßû[ aË¿ tü rð{¡l¡üe rne all¡guil or fila}VcflËnt ang ûts{fåts tå lÞæi¡ftg ì,Fer* t-."} ?**;t*;:. 'iY: s) 6) 7) H-PèKUMAR Projecl No. 17.7-245 -6- shouTd furrher evaluate the exnansion potcntial of the soilç at the tirne olconstructinn. A positive way to reduce the risk of slab movement, which is commonly used in the area, is to construct structurally supported floors over crawlspace. To reduce the effects of some differential movement, nonstructural floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. lnterior non-bearing partitions resting on floor slabs should be provided wirh a slip joint al the bottom of the walt so that, if the slab rnoves, the movement cannot be transmitted to the upper structure. This detail is also important for wallboards, stairways and door frames' Slip joints which will allow at least l% inches of vertical movement are recommended. Floor slab control joints should be usecl to reduce damage due to shrinkage cracking' Slab reinforcement and controljoints should be established by the designer based on experience and the intended slab use. The road base can consist of CDOT Class 2, 5 or 6 agglegate base course, or other similar material such as crusher fines. compacted to at least 957o of the maximum standard proctor density. AII topsoil and loose or disturbed soils should be removed and the subgrade moistened te near optimum and compacted prior to fill placement. The above recommendations will not prevent slab heave if the expansive soils underlying slabs- on-grade become wet. However, the recommendations will reduce the effects if slab heave occurs' All plumbing lines shor.rld be pressure tested before backfTlling to help rec¡rce the pote$tial for w*iting, SURFACE DRAINAGE Pssitive surface drainage is a very important aspect of the project to prevent wetting of the b*¿ci*e scdås b€l(}* the residence. A serir$eter faundation drain *round. shallcrv çrawlsnace areas (less than 4 feet deep) should not be needcd with adequate compaction of foundation wall backfill anrl positive su¡face slope away from foundation walls. The following drainage H-P*KUI\4AR =::þ-rg Þ{s. É?-?-â4S ,7- precautions should be observed during construction and maintained at all times after the residence has been completed: å) lixc€sstve wetilng or drying Õf the fbundaÍion excavations and underslab areas should be avoided during construction. Drying could increase the expansion potential of the soils, 2) Exterior backfill should be adjusted to near optimum moisture and compactcd to ¡lt ¡stitÞL >r-to uL ttìä ulaiillllllffi SlAn{¡Arü ffüg{ûr ilÊnslty tn PåVemem ff€AS ARü ir} ai least90Va of the maximum standard Proctor density in landscape areas. 3) The ground sr¡rface sumounding the exterior of the building should be sloped to drain away from the foundation in all directions. Vy'e recommend a minimum :.;uFÇ ,L'; i.i tãlüslËÈ Ëi'r ¿åBå ?¡r5l !$ fbgt t* unpaved areas and a rninimum slope of 3 inches in the fi¡st 10 feet in paved areas. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy irrigation, such as sod, and lawn sprinkler heads should be located at least l0 feet from foundation walls. Consideration should be given to use of xeriscape to reduce the potential for wetting of soils belorv the building caused by irrigation. LIMITATTONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this ârea ai this time" 'We make no wârranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory boring drilled at the location indicated on Figure l, 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 concemed about MOBC, then a professional in this special field of practiee should be consulted. Our findings include extrapolation of the subsurface conditions identified at the exploratory boring and variations in the subsurface conditions may not become evidenl untii excavaiion is periurnrcd. ir EüR{lrÍrüRs enc{Jl:n[greû üür¡:rË cünsrt¡l*¡üä åFpúå; ru H-P*KUMAR Projecl No. 17-7-245 -8- be different from those described in this rcport, we should be notifTed at olrce so re-evaluation of lhe recnmmen¡ìxfi¡rnt årråv he- ¡E¡s:ì* This report has been prepared for the exclusive use by our client for design purposes. 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 constructíon to review and '¿rls3i¡€istfks iriepåerrle*tatien sf cur recsmrnendatiüns, and te verify that the rsccrnmendâtions have been appropriately interpreted. Significant design changes may require additionat analysis or modifications of the recommendations presented herein. We recommend on-site observation ofexcavations and foundation bearing strata and testing of structural fill by a representative of the geotæhrrrcar e*prtter. Respectfully Submitted, H-PS KUMAR ,r.a-"-1, Fhu,ir!A Vn,ns ÞF**4t rv n, c æ*5, c .r-;,$Þ g?-*t* DAY/ksw AndersonStructuralEngineering:.LandonAnderson0¿udgMl Carla Ostberg (cadA.ortbereQ gmail.com) cc: lJ {!èt/¡l*ttFr Þraia¡t l\ln l?-?-9áç couNTY ROAD 214 (PEACH LOT2 i:?a è-'g** u!/\Jtrt r ìrvnu c|* PROPOSED ARENA WAHË BORING 1 ñhññ^ñÊà ¡s--SrÊF¿.È,1ñË-3$XJçftftrE PROPOSED BARN IItr ¡ /*-\- OITCH ffi50 0 50 r00 .! ttrrEL=ÂrÉÈ1tL ó';¡ir-a-lla i o 17 -7 -245 H.PryKUMAR LOCATION OF EXPLORATORY BORING Fig. 1 r* fì -5 -_ t0 BORING I !:T? I-EGEND ñtff"jtli? n Ì0PSottr ORcANtc sANDy stlTy cLAy, r¡RM, M0tsi, DÅRK gR0ltN. CLAY (CL): VERY SAN0Y, SILTY, STtFr, MOtSl, LTGHT BR0WN. SCÀTTFRII) ORAVÊL AND COEBLE I{ITH DTPIH, LOI¡I PI-ASÌIC'TY, CLAY (CL); SAN0Y, VtRy STtrr I0 HARD, Motsr, BR0,¡íN, MID|UU PtASf¡cril. 15/12 IVC=6.6 tD=110 5ol5 WC=8.5 fÐaBS -i¡}$={S 2e/t2 VIC: 1 2.3 DD=ll4 4t /t2 ¿ô,.1? 44/ t2 ti/C= I 4.0 DD:l f 2 24/ t?. {r,f i } I Tì !lçî.ta *ìrr:¡{ f, .: -.ã.}jt* ,, ll i;lt.tìg}¡ìå ¡ }Ë-!giì rå¡j*¡ 5r 157¡2DR|VE SAMPLT BL0!v C0UNT. INDICATES THAT t5 BLOÌYS 0F, I4O-POUND HAMIITR ÊALLINC 30 INCHTS WERf RTOUIRTD SAMPLIR I2 INCHES, NOTES A TO DRIVT IHT LJ L¡Jl! Ifl F-.L o ?. l{Jt IXTL*EITçFï gûffiqr TdÅs ÐRiLLfi] û]t i.ìåÊf* 3r, ?s:? 1_È]Ì$t À4-ilr\,n utAnlLtt m LUi{¡|NUUUS tUUHt futf LH AU$}-H. IHT LOCÂTION OF THT TXPLORATORY BORINO WAS MIASURTO APPROXIMATTLY BY PACINC FROM FEATURES SIJOWN ON THT SITI PLANDo^r'lñrñ r¡rôni r ^rrKUV¡ULU. MIUULL UI r(UHUSLU HTS|[JLNC[, \TÀS ÍIELD STAXED EY CLIINT, ¡, THT TLTVATION Of 'HI EXFLORATÛRY BORING ViAS NOT MTAIUREO ÂND Tåi{ å*€ +t Íå¡{ {spt4sÂt*&v e&â*¡ê ,5 fg.ûñÊ$ TS S{pr$. 1. Ï}tt TXFLORATOflY BORING LOCATION SHOULD BT CONSIDTRTÐ ATCURA]T ONLY TO THT DTGRTT IMPLIED BY THT MTTHOD UsTD. __t1 5. THT LINES BEIWTEN MATERIALS SHOWN ON THI IXPIORAIORY BORING LOG RËPRESINT IHE ,\PPR0XllitÄTt BOUNDÀR|IS BÛ}YIEN MÂftRtAL Typts ÂND THt IRANSITI0NS lilÄY Bt GRA0UAL. 6. GR0Ul.lDryÂTlß WÅS I'l0T tilc0uNrtftti! ,N IHf t0âtJ,tö AI T¡¡[ Ttålt 0s t*lL1"11{{i. IÁBORATORY TEST RTSULIS: liC = WÅTIR c0NÍtNT (r) {ASTH D 2216); 0D = 0RY OENs|IY {pcl) (ASTM D zzt6);*200 = ptRCtNrAGt pÂSStNG N0. ?00 Sttvt (ASTM 0 !t40). -50 LOG üF IXPLORÀTORY SORING fiç. 21 ?-?*245 H-PryKUf\4AR SÂMPLE OFr Very Sondy Sílly Cloy FROM:Boringl@2.5' WC = 6.6 %, DD = ll0 pcl ¡ i3FÅlisi{* i,å}¡ã}å4 **ñs?Al*T PftËssÜRT UPÛN WETTING 2 fr )Jt¡l3ø ättr Õ J()az.() (J t.0 ÂPPUED PRESSIJRE - K$f to \ 2 -3 i i¡ J I t0ô þ 17 -7 *245 H-PryKUMAR SWTLL_CONSOLIDATION TTST RESULT Fig. 5 SAMPLT 0F: Sondy Cloy FROM:Boringl@7,5' WC * f2,5'l, DD = 114 pcf 6 4 3 e¡i'¡r¡i¡¡í¡¡'ç Urrultt ü{,ñSTAñI PRESSURE UPON WETTING 2 0 JJ l¡J*tll I zotr ¿])() tnz.ot't -2 -3 tü 17 -7 *245 H-PryKU]VIAR SWELL-CONSOLIDATION TËST R[SULT Fis, 4 I SAMPLE OF: Sondy Cloy FROM:Boringl@15' WC = t4"0 t, Þt = it? pct 4 5 EXPANSION UNDER CONSTÀNT PRESSURE UPON WETTING 2 0 N JJ 3ul I zo Ë ô J c)tnz -1 { z. -3 -irl 1t ¡¡ it it I { ì,å åFí,i¡ÈS Fî3ãÈi3ãF * iSF lt 38t t7 -7 -245 H.PVKUMAR SWILL-CONSOLIDATION TTST RTSULT Fig. 5 H-PThUMARTABLE 1SUMMARY OF LABORATOßY TEST RESULTSProiet rHCI.1I'7-245sotLwP}ÍVeqy Sandy SiltyCIarVery Sardy Silr CIay q¡ith GnvelSandy ClaySaudy ClayUI{CONRNEf)copRËssrvESTRËNGTHfPSF}PIASTICINDEXlolnlu(rulDL$NITf/61PERCE¡¡TPASSINGNO.200stÊvE59SAND(olotËRAVEL(wNATURALDRYDENSITY{ocflr1098114112NATURALTIOIgTUREcot{TEf{T{Yøl6.68,512.3r4.$;LOCATIONÞEPTH{ftt2V257n15sÂtPI-BORINGI