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Home My WebLink AboutSubsoil Study for Foundation Design 02.21.18t:,j -- i i;''',sv il l' llj] i-:-'.ì..,. Ì.i 5020 County Road 154 Glenwood Springs, C0 81601 Phone: (970) 945"7988 Fax (970) e45-8454 Email: hpkglenwood@kumaruså.com g.;;,:¡r;.i:l :r,iiri i -'r1..i¡..,..'iri-¡, ¡ l :l:¡t¡i; : i r¡it ;."r !!.r:t -.';: .1¡ '' .;i;. 1'r'.¡ ''',¡. ii:tt' ;' n';'::;'": Office Locations: Denver (HQ), Parket Colorado Springs, Fort Collíns, Glenwood Springs, Summii County, Colorado sws0åL s'm]ÐY F'OR. F'OUNN,q T{TN ÐESNGN PROFC}SEÐ RESTDtrI{C]E r,cÞT' f"o, FÐacH vA.[,r,EY acR.Es T'BÐ CÛUNT'V ITOAW 214 GARTIXEI-N COUNTY, CGT-ÛRAÐT Jots N0.18"7-139 FiEBRUÁ.RY 2X.,2CIn8 PRIEPÁ.RIED FOR.r MTXCXT,AET, IWüI.T,O E96 COUN1IY R.OA,D 266 s{LT.' CtX,CIRAÐO 8X652 [qr¡Ërui¿lr:-9-qq,isglìÐ -¡Þæ 'lt'aHLE OlF c()lvll'luÀ,1'll-s PURPOSE AND SCOPE OF ST{JDY PROPOSED CONSTRUCTION SITE CONDITIONS FIELD ÐGLORATION SI'BSURFACE CONDMIONS FOI.INDATION B EARING CONDITIONS DES]GN RECOMMENDATIONS IìOUNDATIONS..... FLOOR SLABS....... UNDERDRAII'{ SYSTEM SURFACE DRAINAGE ... I-IMITATIONS .) -3- -3- n-L- 5 -6- À-s- -5- FIGIIRE 1 - LOCATION OF EXPLORATORY BORINGS FIGURE 2 _ LOGS OF EXPLORATORY BORINGS FIGTJRE 3 - LEGEND AND NOTES FIGTIRE 4 S}VELL-CONSOLIDATION TEST RESULTS TABLE 1 - SUMMARY OF LABORATORY TEST RESIJLTS -1- ..-1- 1 -') _ i=l-i¡,:+ri<¡.ií1.,t/ut rt* Proiect t{o. 1B-7-139 PIUP"]POS]E A.IND SCOPE OF' S]RUJDY This report ptesonts the results of a subsoil sfudy for a proposed residence to be located on Lot 10, Peach Vailey Acres, TBD County Road 214, Garfield County, Colorado. The project site is shown on Figure 1. The purpose of the study was to develop recomtnendations for the foundation design, The study was conducted in accordance with our proposal for geotechnical engineering services to Michael Mello dated January 3L,2018. A field exploration program consisting of exploratory borings was conducted to obtain information on the sribsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to deteimine their classifi.cation, cornpressibilit-y or swell and other engineering characteristics. The results of the field exploration and iaboratory testing were alalyzed to develop rscoTrunendations for foundation types, depths and allowable pressures for the ploposed building foundation. This report summarjzes rhe dnta obtained during this siudy and presents oru conclusions, design t'ccommcnrlation.s and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encoilntered. PRO ['ÛSEÐ COINSTRUCT]IONI The proposed residence will be a one story wood fiame stn-lchlre above a crawlspace and with an attached garage. Garage floor wil1be slab-on-grade. Grading for the structure is assumed to be relatively minor with cut depths between about 2 to 4 feet. We assllme relatively light foundation loadings, typical ofthe proposed type ofconstruction. Ifbuilding loadings, location or grading plans change significantly from those descdbed above, we should be notified to re-evaluate the recorn¡riendations contained in this reporf. sltT'lE cONDnT[Oi\Ts The property is 2.0 acres and located to the south of County P.oadZl{ @each Valley Road) and orr the east side of Peach Lanc, The neighbot's gravel driveway lies along the nofth lot line. Vegetation consists of grass and weeds. The gronnd surface is relatively flat with a sligh[ slope down to the south. Ë{..rË<"-"1,ilJfr.{ÁLiÌ Proleci t\o. 1B-7- 139 ¿) -b- FTET.D ]EXF]LO]RAT'IONT The fie1d exploration for the project was conducted on February 1, 2018. Two exploratory borings were drilled at the locations shorvn on Figure 1 to evaluate the subsudace conditions. The borings werc advanced with 4 inch diameter continuous flight augers poweied by a h'uck- mounted CME-458 drill rig. The borings were logged by a re¡:resentative of H-P/I{umar. Samples of the subsoils we¡e taken with a 2 ll;rch I.D. spoon sampler. The sampler was driven into the subsoils at varions depths with blows f¡om a 140 pound hanrmer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-1586. The penetration resistance valt¡es are an indication of the relative density or consisfency of the subsoii..s. lle¡lhs at which the samples we.Te tåken and the penctration resistance values ate shown on the Logs of Expioratory Borings, Figure 2. The samples wele retumed to oul laboratory for review by the project engineer and testing, S U]ESIIRTA.C]E CONDITNONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. .The subsoils, below al¿otttl/z foot of topsoil, consist of'about 3t/z feet of stiff to very stiff, silty sandy clay over{ying medium dense to stiff, silty sand and clay down to the maximum explored depth of31 feet. Laboratory testing performed on samples obtained from the borings included natural moisture content, density and finer then sand size gradation analyses. Results of swell-consolidation testing performed on relatively undisturbed drive samples of silty sand and clay, presented on Figure 4, typi.cally indicate low to moderate compressibility under conditions of loading and wetting and iow collapse pofential (settlement under constant load) when wetted. A sample from Boring 2 aL 5 feet sl-rowed a low expansion potentiai when wetted. The laboratory testÏng is summarized in Table 1. Free water was not encountercd in the borings at tlle time of ddlling. 'When checlced 4 days later, tlre f¡ee watcr levei in Boring 1 u'as at Z7lzfeet in dcpth. The subsoils were sliglrtly inoist to wet below gr"oundwater level. ù.d,,irärÍ¿iijl\,¡T,åj:l Project No. 1B-7-139 -J- F'O[TI\IDAT'[O1V ts]EI\RT}f G CCINIDIT]I.OINS The silty sand and clay soils encountered in the boring possess low bearing capacity and, from our experience in the area, typically tend to compress when they become wefted. Lightly loaded spread footings should be feasible for foundation support of thc residence with some risk of iltovenent. The risk of movement is primarily if the bearìng soils were to becomc wetted and precautions should be taken to prevent wetting. Sources of wetting include excessive inigation near the foundation, poor surface fuainage adjacent to foundation walls and utility line leaks. The excavation should be observed by a representative of the geotechnical engineer. Any expansive clay soíls encountcleci at bearing levcl in the excavation should bc renlovecl anrl replaced by compacted structLtral f,ll. DESXGN RECOII4IVflOIVDAIIIONS FOLTNDATIONS Consideríng the subsurface conditions encoltntered in the exploratory borings and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural soils or compacted structu¡al fill' The design and constunction cdferia presented below should be observed for a spread fooling foundation system. 1) Footings placed on the undisturbed natural soils or compacted structLlral fill should be desígned for an allowable bearing pressure of i,500 psf. Based on experience, we expect initial settlement of footings designed and conshucted as discussed in this section will be aboui 1 inch or less. There could be additional movsmcnt if the bearing soils become wetted of about 1/zto f. inch depending on the depth and extent of the wetting. Z) The footings should have amini¡num width of 18 inches for continuous walls and 2 feet for isolated Pads. r ¡ f:i._..,¡ ì1 J,1 n'- 3) -4- Exterior footings and footings beneath unheated areas should be provided with adequate soil cove¡ above their bearjng elevation for fiust protection. Placement offoundations at least 36 inches below exterior grade is typically used ín this afea. Continuotls fcrunclation walls shor¡ld be reinfo¡ced top and.bottom to span local anomalies such as by assuming an unsupported length of at lcast 14 feet. Foundation walls acting as retaining strucfirres should also be designed to resist a lateral eiuth pressure coüesponding to an equivalent fluid unit weight of at least 50 pcf. The topsoil, expansive clay soils and any loose or disturbed soils should be removed from thc building area and rcplaced with structural fill or'lhe footing bearing level extended down to the natural soils, The exposed soils in footing area should then be moistened and compacted. Structural fill below footing grade should consist of imported 3/a-inch.road base compacted to at least 98% of the m¿rxiurunr standard Proctor density at a moi.sturr'content ncar o¡rtinrnm. A representative of the geotechnical engineer should obsqrve all footing excavalions prior to concrete placement to evaluate bearing conditions. 4) FLOOR SLABS The natural on-site soils, exclusivo of topsoil, are suitable to support lightly loaded slab-on-grade consttuction. Expansivo clay soils should tre removed and can be replaced with compacted st¡uctural fiii. To reduce the effects of some differential rnovement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained veriical movement, Floor slab control joints should be used to reduce damagc- due to shrinkage craching. The requirements for joint spacing and slab reinforcement should be established by thc designer based on experience and the iniended slab use. A minimum 4 inch iayer of free- draining gravel should bt-' placed beneath slabs to facilitate drainage. This material should consist of minus 2 inch aggregate with at least 507o retained on the No. 4 sieve and Tess thanZ%o passing the No, 200 sieve. s) 6) !-i'F'.Ì¡ ;'T, l[\'./ll,rti Project T'Jo. 1B-7"'i39 -.t - Alt fi,li materials for suppori of floor slabs should be ðompacted to at ieast 95Vo of maximum standard Proctor density at a moisture content nêar optimum. Required fill can consist of imported 3/c-inchroad base devoid of vegetatioh, topsoil and oversized rock. UNDERDRAIN SYSTEM For the proposed shallow crawlspace and slab-on:grade garage, a foundation drain system is not required, It has been our experience in the alea that local perched groundwater can develop auring times of heavy precipitation or seasonal runoff. Frozen ground. during spring runoff can also create a perched condition. 'We recommend below-grade constmction, such as deep crawlspace (over 4 feet) and retaining walls, be prctected from wetting and hydrostatic pressule buildup by an underdrain system. The drains should consist of drainpipe placed in the bottom of the wall backfill sunounded above the i¡rvert levcl rvith frce-draining granular ¡ualeúal. The drain should be placed at least 1 foot below lowest adjacent finish grade and sloped at a minimumlØô to a suitable gravity outlet. Free-draining granular material used in fhe underdrain sysiem should contain less than 27o passing the No. 200 sieve, less than 507o passing f.he No. 4 sieve and have a maximum stze of 2 inches. The drain gravel baclcfill should be at least LYzfeet deep. SURFACE DRAINAGE Positive surface drainage is a very important aspect of the project to prevent wetting of the bearing soils. The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: 1) Inundation ofthefoundation excavations and underslab areas shouldbe avoided during construction. 2) Exterior backfill should be adjusted to near optimum moisfure and compacted to at least 95Vo of the maximum standard P¡octor density in pavement and slab arcas and to at least 9OVo of thø maximum standard Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away fromthe foundation in ali directions. 'We recommend a minimum Ï,'l-[arvi".îJlt /iliiì ProjecÍ ftlo. 18-7-139 -6- 4) slope of 12 inches in the first 10 feet in unpaved areas and a minimum siope of 3 inches in the first 10 feet in paved areas. Free-dlaining wall backf,rll should bo covered with filter fabric and capped with about 2 feet of the on-site soils to reduce surface water infiltration. Roof downspouts and drains shoulcl discharge well beyond the limits of all bacldill. Landscaping which requires regular heavy irrigation should be located at least 10 feet ftom foundation walls. Conside¡ation should be given to use of xeriscape to reduce the potential for wetting of soils below the building caused by irigatiou. I,III!flIIIATNONS This study has becn conducted in accordance with generally accepted geotechnicai engineering princþles and practices in this area aÍthís time. 'We make no wananty either expross or implied. Thc conclusions and rccommcndations submittcd in this rcporl arc bascd upon the data obtained from the exploratory borings drilled at the locationsindicated on Figure 1, 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 ftiture. ff the client is concerned about MOBC, then a professional in this speciai field of practice should be consulted. OLrL lindings include interpolation and extrapolation of the subsurface conditions identified at the exploratory borings and variations in the .subsurface conditions may not become evident until excavation is performed. If conditions encountered during consttuction appear different û'om those described in this report, we should be notified so ihãt le-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by oul client for design purposes. 'W.e are not responsihle for technical interpretations by others of our i¡fbrmation. As the project evolves, we should províde continued consultation and fielcl setvices during construction to review and monitor the impiementation of our recommendations, and to verify that the recommendations have been appropriately interpreted. Significant design charrges may require additional analysis 5) ú{-!.';:yí.'1jtia2,.Fì Prcjeci frlo. 18-7-139 -1 - Õt modifications to the recommendations presented herein. \Me reco'nrmend on-site observation of cxcavations and foundation bearing süata and testing of structural fil1by a represeütative of the geotechnical engineer. Respectfu lly S ubmitted, t={-F* KUfr/TrqR , '. t.*'l- . Shane M. Mello, Staff Engineer Reviewedby: t â,å44(?z .:-r -., I :.':ì vI Daniel E. Hardin, P SIVIM{kac t ,',L I !^ it: ]1ÞF"l,[$.iú'L&iÏl Frcieet tilo, ì8-7-'i 39 LOT ì1 ,t I I ¡ 0 I I 0 SORING 2 lJl 5 To<(IJ(L L@T .0O o FORING 1 LOT 9 tt I Í l{ 'n T I. I d ¡I 5U Fis. 1LOCÀTION OF EXPLORATORY BORINGSH-Pryü<UfiVilAR1 B-7* 1 3s APPROXIMAÍE SCALE*IIET BORING 1 BORING .2 0 5 12/12 14/ 12 WC=6.8 DD=1 1 5 -200=64 16/12 WC=6..6 DD=1 O4 2Ð/12 WC=8.7 DD=1 14 22/12 s/12 s /12 I zs¡tz' WC=6.4 DD=1 I 6 31/12 WC=8.5 DD=1 1 7 ! rc/n I rs¡tz' wc--7.3 DD=1 1 2 | rc/tz o '10 't5 25 30 JJ i0 15 2A 25 50 35 22/21 Lü ¡ilt! I !- rrJ LlJ LL I:c¡- D.IJ6 20 I I ñ Fig, 2LOGS OF EXPLORATORY BORINGSH-PryE(UFMAR1 B-7- 1 39 LEGËND u TOPSOIL; ORGANIC SILTY SANDY CLAY, FIRM, MOIST, DARK BROWN CLAY (cL); SILTY, SANDY, STIFF TO VERY STIFF, SLIGHTLY MolsT, BROWN. SAND AND CLAY (SC_CL); SILTY,- MEDIUM DENSE, SLIGHTLY MOIST TO WET, LIGHT BROWN TO BROWN. RELATIVELY UNDISTURBED DRIVE SAMPLE; 2-INCH LD. cÀLlFoRNlA LINER SAMPLE.! 12/12 ÐRIVE 5AMPLE BLOW COUNT. INDICATES THAT 12 BLOWS OF A 140_POUND HAMMER FALLING 30 INCHES WERE REQUIRED TO DRIVE THE CALIFORNIA OR SPT SAMPLER 12 INCHES. 4 ogpru To WATER LEVEL AND NUMBER oF DAYS AFTER DRILLING MEASUREMENT WAS MADE --r+ DEPTH AT WHIOH BORING CAVED FOLLOWING ÐR|LL|NG. NOTES 1. TII[ TXFLORATORY OORII{o5 WERT DRILLED OII TTBNUARY 1" 2018 WITII A 4INCII DIAMITIR üUN INUÜUS fLIÛHI' PÜWER AUGER. 2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE NOT MEASURED AND THE LOGS OF THE EXPLORATORY BORINGS ARE PLOTTED TO DEPTH. 4, THE EXPLORATORY BORING LOCATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIEÐ BY THE METHOD USEÐ: 5. THE LINES BETWEEN MATERIALS S.HOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRAN5ITIONS MAY BE GRADUAL. 6. GROUNDWATER LEVEL SHOWN ON THE LOG WAS MEASURED AT THE TIME ANÐ UNDER CONDITIONS INDICATED. FLUCTUATIONS IN THE WATER LEVEL MAY OCCUR WITH TIME. 7. LABORATORY TEST RESULTS: WC = WATER CONTEI.IT (%) (ASTM D 2216); DD = DRY DENS|TY (pct) (aSrM O 2216); _2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D 1140). LTGIND AND I'IOTTS Fig,31 B-7* 1 39 H-Pryfi<UN4AR SAMPLE OF: Silly Sond ond Clo¡, FROlvl: Boring 1 @ 1ü' WC = 6.6 24, tt = 104 pcl t,i JJl¡l vl I z.() tr ô:io 4nz.o(J 0 ¡...¡ ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUT TO WETTING -l -2 -3 -4 *5 i.o ÂPPLIED - KSF 10 100 SAÌ,IPLE OF: Silty Sond ond CloY FROM:Foring2(J,5' \hlÇ = tt,4 2í, DD = 116 pcf \ô JJtrj t/'t I zotr â =() U)z,o() 2 fXF¡\NSlOl.l Ul'IDER ÇOl'¡STAI'lI PRTSSURE UPOI'I V/ITTII.IG 0 -1 -2 - lrÞlieó pnÈssunE - t<i'r -z L0 Fig. z!H-Pryfl,(JIVilAR1B*7 *139 SWILL-CONSOLIDATIOhI TEST RESULTS F{*PryKt1im*4AF.1 TF-¡B[-E'l SLO [{lù [T4Æ\RV O F N-ABO RI\]ICIRY IIES]T [R ES [J LTS Project No. 18-7-'139 DEPTH (fr) NATURAL MO¡STURE CONTËNT NATURAL GRADAÎION DRY GRAVEL 'OAO--.DENSIÍY (rí,) (9i,) (pcfJ PERCENT PASSING NO.200 SIEVE UNCONFINED COMPRESSIVE STRENGTHBORING TIONSAMPLE (9i)lpsÊt ATTERBERG LIMITS I LìeurD pusrrc iLIMIT ì INDEX ß/.\ \ tn/"\ SOIL TYPE 1 5 10 64 I SiltY Sandv Clov6.{ì (t.6 { l) 1 {).1 I Sill,r Sand and Cial' j slttl'sonã ooo ctol'15 1t.r I 117ìt j Sil¡'Sancl5'Cla1 5 ó.-1. 1 16 Silt¡r Sand aud Clay :0 I i Siltv Sancl and Cla¡-7.3 11: I i il:l] _- -.i; iþ 1 1,r,' U NlilA:i",i, 5020 County Road 154 Glenwood Springs, C0 81601 Phone: (970) s45-7988 Far (970) e45-8454 Email: hpkglonwood@kumarusa.com r$.-,- r'r;,¡:1:r'i,'r:i -l'¡i.,¡¡;,;ri,¡r'¡ , ;i:n:;"t,,ii:,'il;. i *¡.i ::.'t ..''' :ii ì':,.,r ''.',': . ' ì::tf' :' ¡;;,'i; ", ' Office Locationsl Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado SUSSOTL STUT}V F'OR. F'OUNÐ,ÀTTON ÐESNGN PROFOSEÐ RESTDEI{CE r,oÏ' f,o, FÐacrr vAr,r,EY,ÀcREs T'EÐ COUNT'V ITOAÐ 274 G.AR FIET.D CO{JNT'Y, CGl,ORÁ.Ðt J0ts hlo.lE-7-139 FTEBRUARY 2X.,20n8 PIRIEPA,R.ED IFOR¡ hÆNC{TAET, T\4T'T.tr.CI 896 COUN1TY R.OAD 266 s'{LT, COr-0RAÐC} 81652 ã* T'AtsLE OIT CONT'EN.I]TS PURPOSE AND SCOPE OF ST{.IDY PROPOSED CONSTRUCTION 1 1 SME CONDITIONS FIELD ÐGLORATION SIIBSURFACE CONDMIONS FOTINDATION BEARING CONDTTIONS ... ......... . DESIGN RECOMMENDATIONS,..., IìOUNDATIONS ............. FLOOR SLABS UNDERDRATN .SYSTEM SURFACE DRAINAGE t-tMt'l'Ät'l()NS FTGIIRE 1 - LOCATION OFEXPLORATORY BORTNGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGIJRE 3 _ LEGENI) AND NOTES FIGURE 4 _ S}VELL-CONSOLIDATION TEST RESULTS TABLE 1 - SUMMARY OF LABORATORY TEST RESULTS ^)- i J_ ...- 3 - ',,-3 - ...- 4 - ..,- 5 - _{_ ,....* 6 - ti-11.19'l¡.r.1í\.,,1P'_jì {â* Project lrio. 18-7-139 I PJURPOS]g AIND SCOPE CI]F S]ruNDY This rcport ptesents the results of a subsoil sfudy for a proposed residence to be located on Lot 10, Peach Valley Acres, TBD County Fioad,Zll, Garfield County, Colorado. The project site is shown on Figure i. The purpose of the shrdy was to develop recotntnendations for the foundation design, The study was condncted in accordance with our proposal for geotechnical engineering services to Michael Mello dated January 3L,2018. A field exploration program consisting of exploratory borings was conducted to obtain info¡mation on the subsurface conditions. Samples of the sutrsoils obtained during the field exploration were tested in the laboratory to detetmi¡e their classification, cornllressibiüt-y or swell and other engineering characferistics. The results of the field exploration and laboratory testing were analyzed [o deveiop rscommendations for foundation types, depths and allowable pressutes for the proposed building foundation. This report summadzes the d¿rta obtaíned during this study and presents our conclusions, design tcconimcndations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSEÐ CONST'RUCTXONT The proposed residence will be a one story wood frame structure above a crawlspace and with an attached garage. Garage floor will be slab-on-grade. Grading for the structute is assumed to be relatively minor with cut depths between about 2 to 4 feet. \Ve assume relatively light foundation loadings, typical of the proposed type of co¡rstruction. If building loadings, location or grading plans change significantly from those described above, we should be notified to re-evaluate the recomniendations contained in this report. SÍ1I]O CONDNTNONTS The property is 2.0 acres and located to the south of Connty Road 2I4 @each Valley Road) and on the east side of Peach Lane. The neighbor's gtavel driveway lies along the nofth lot line. Vegetation consists of grass and weeds. The gronnd surface is relatively flat wirh a slight slope down to the sottth. r'f .,1Ì1.¡!,lJli.rll¡ll Projeci i\o. 10-7-'139 ô ü][E]LID EXIP]I,OIR A,IITONT The field exploration for the project was conducted on February 1, 2018. Two exploratory borings were drilled at the locations shorvn on Figure 1 to evaluate the subsudace conditions. The borings were advanced with 4 inch diameter continuous flight augers powered by a h'uck- mounted CME-458 drill rig" The borings were logged by ale¡:resentative of H-P/I{umar. Samples of the subsoils were taken with a 2 roLch I.D. spoon sampler. The sampler was driven into the subsoils at vzuious deptits with lriows f¡orn a 140 pound hanrmer falling 30 inches. This test is simila¡ lo the standard penetration test dsscribed by ASTM Method D-1586. The penetiation resistance values are an indication of the relative density or consistency of the subsoils. Depths at which the samples were taken and the penctration iesistanco values ale shown on the Logs of Expioratory Borings, Figure 2. The samples \4'ere returned to oul iaboratory for review by the project engineer and testing, S INESURTÁ.C]B CONIDTT'IONS Graphic logs of the subsurface conditions encounteted at the site a¡e shown on Figure 2. .The subsoils, below aboutl/zfoot of topsoil, consist ol'about 3Vz featof stiff to very stiff, silty sandy clay over{ying medium dense to stiff, silty sand and ciay down to the rnaximum explored depth of31 feet. Laboratory testing performed on samples obtained from the borings included natural moisrure content, density and finel then sand size gradation analyses. Results of swell-consolidation teSting performed on relatively undistr-rrbed drive samples of silty sand and c1ay, presented on Figure 4, typically indicate low to moderate compressibility under conditions of loading anti -wetting and low collapse potential (settlement nnder constant load) when wetied. A sample from Boring 2 at 5 feet showed a low expansion potential when wetted. The labo¡atory te.sting is summarized in Table 1. Ftee water was not encountered in the borings at tlle time of drtlling. 'When checlced 4 days later, llre f¡ee water levcl in Boring 1 rvas at 2lVzfeúin dcpth. The subsoils were slightly rnoist to wet below groundwater level, Froject No. 'lB-7-139 -3- ]FOIJi\ID,A.T']IOftI ts]EI\R]ISI'G COIVDITNOINS The silty sand and clay soils encountered in the boling possess low bearing capacity and, from our experience in the area, typically tend to compress when they become wetted. Lightly loaded spread footings should be feasible for foundation support of thc residence with some risk of movement. The risk of movement is primarily if the bearing soils were to becomc wefied and precautions should be taken to prevent wet[ing. Sources of wetting include excessive inigation near the foundation, poor surface drainage adjacent to foundation walls and utility line leaks. The excavation should be observed by a representative of the geotechnical engineer. Any expansive clay soils encc¡untcreci at bearing levcl in the excavation should bc lenlovecl and replaced by compacted shuctural fili, ]DESTGN RECOÞdMEßIDA"TIO¡{S FOLTNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nahtre of the proposed construction, we recommend the building be founded with spread footings bearing on the natural soils or compacted structural fiIl. The design and construction cdteria p¡esented below should be observed for a spread footing fóundation system. 1) Footings placed on the undisturbed natural soils or compacted slruchrral fill should be designed for an allowabÌe bearing prcssure of i,500 psf. Based on experience, we oxpect initial settlement of footings desþed ard constructed as discussed in this section will be about 1 inch or less. There could be additional movemcnt if the bearing soils become wetted of about l/zto f. inch depending on the depth and extent of the wetting. 2) The footings should have a minirnum width of 18 inches for conti¡uous walls and 2 feet for isolated pads. F I i.:,_.._¡ îa j ,1 n.- 4 3)Exterior footings and footings beneath unheatetl areas should be provided with atleqirate soil covet above their bearjng eJevation for frosl protection. Placement of foundations at least 36 inches below exterior grade is typically used ín this area. Continuous foundation walls should be rei¡forced top and botiom to span local anolnalies such as by assuming an unsupported length of at lcast 14 feet. Foundation walls acting as retaining structures should also be designed to resist a lateral eartlt pressure coüesponding to an equivalent fluid unit weight of at least 50 pcf. The topsoil, expansive clay soiJs and any loose or disturbed soils should be removed from the building area and replaced with skuctural fill or'lhe footing bearing level extended down to the natural soils, The exposed soils in footing area should then be rnoistened and compacted. Structural fili l'relow footing grade should consist of imported n/d-inch. road base compacfed to at least 98% çf. tltç m¿rxiirnnl standard Proctor densitlt at a moisturr content ncar o¡;timtrm. A representative ofthe geotechnical engineer should obsgrve all footing excavations prior to concrete placement to evaìuate bearing conditions. 4) FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade construction. Expansive clay soils should be removed and can be replaced with compacted structut'al fill. 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 damagu' 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 4inchlayer of free- draíning gravel should bc placed beneath slabs to lacilitate drainage. This material should consist of minus 2 inch aggreçate with at least 507o retained on the No. 4 sieve and less ThanL%a passing the No. 200 sieve. s) 6) f-i-F+l:.:rf 5'...+lç: Project 9'.1o. 1B-7-'r39 - .) - All fili materials for support of floor slabs should be òompacted to at 1east95% of maximum standard Procfor density at a moisture ¿:onfenf nea¡ opfimum, R.equired fiIl can consist of imported 3/+-inchroad base devoid of vegetation, topsoil and oversized rock. TINDERDRAIN SYSTEM For the proposed shallow crawlspace and slab-on:grade garage, a foundation drain system is not required. It has been our experience in the area that local perched groundwater can develop duriïg dmes of heavyprecipitation or seasonal runoff. Frozen ground during spring mnoffcan also create a perched condition, We recornmend below-grade construction, such as deep crawlspace (over 4 feet) and retaining walls, 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 invcrt levcl rvith frce-rlraining granular rriaLerial. The drain should be placed at least 1 foot below lowest adjacent finish grade and sloped at a minimuml%o to a suitable gravity outlet. Free-draining granular material used in fhe underdrain system should contain less than 27o passing the No. 200 sieve, less than 50% passing Lhe No. 4 sicve and have a maximum size of 2 inches. The drain gravel baclcfill should be at least LYzfeet deep. SURFACE DRAI\IAGE Positive surface drainage is a very important aspeci of the project to prevent wetting of the bearing soils. The following drainage precautions should be obselved during construction and maintained at all times after the residence has been completed: 1) Inundation of the foundation excavations antì underslab æeas should be avoided during construction. 2) Exterior backfill should be adjLrsred to neâr optimum moistu¡e and compacted to at least 95Vo of the maximum standard Proctor density in pavement and slab æcas and to at least 9AVo of t}:re maximum standard Proctor density in landscape areas. 3) The ground surface surounding the exterior of the building should be sloped to drain away fromthe foundation in a-11 directions. 'We recom¡nend a minimum lil -Flrei{Jir,j.rÉilì Project ltlo. 1B-7-139 -6- 4) 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 paved areas. Free-dlairúng wall backfill sirould be covered with filter fabric and capped with about 2 teæt of the on-site soiis to reduce surface water infiltration. Roof clownsponts and clrains shor.rlci discharge weli beyond the limits of all baclcfill. Landscaping which requires regular heavy irrigation should be located at least 10 feet fi'om foundation walls. Consideration should. be given to use of xeriscape to reduce the potential for wetting of soils below the building caused by irrigation. [,Ilbflt1lA1t[ONIS This study has becn conducted in accordance with generally accepted geotechnical engineering princþles and practices in this area at this time. .We make no wan'anty eithe¡ express or implied. The conclusions and rccommcndations submitted in this report are based upon the dafa obtailetl f¡om the exploratory borings drilled at the locations jndicated on Figure 1, 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 ftiture. If the client is concetned about MOBC, then a professional in this special field of practice should be consulted. OuL lìndings include ínterpolation and extrapolation of the subsurface conditions identified at the exploratory borings and va¡iations in the.subsurface conditions may notbecome evident until excavation is performed. If conditions encountered during construction appear different from those described in this report, we should be notified so ihat re-evaluation of the recommendations may be made. This report has been prepared for the exclusive use by our client for desigrr purposes, 'We are not responsible for technical interpretations by others of our i¡fonnatïon. As the project evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recornmendations, and to verify that the recommendations have been appropriately interpreted. Signifi.cant design changes may require additional anaiysis 5) ü{-þt.ri'#tvùâ,fì Prcjeci tilo. 1&-7-139 -7 - or modifications to the recommondationir'presented horein. \Me reco'rnmond on-sito observation of exoavations and fountlaLio¡r bcuiug sfrata and testing of structut'al f,Il by a repteseutative of the geotechnical engineer. Respectfully Submitted, ü'-{-P* KUft/f/qR . i ,..-,.,:ì-' . Shane M. Mello, StaffEngineer Reviewedby: ''-!.':17 !:.':: Daniel E. Hardin, P SMlMlkac f)"iL AL I ,'¡-it+liíiËi&*'J? Froieet trlo. l8-7-139 L@T TI EORING 2 o lljzJ :Eo l¡Jo- L@T 1S o BORING 1 L@T g tt I i{ q t. I d Iì ã g 0û50 H-Pryü<UNIIAR LOCATION OF EXPLORATORY BORINGS Fig. 11 B-7* 1 3e APPROXIMATE SCALE.IIET BORING 1 BORING ,2 00 5 12/12 14/ 12 WC=6.8 DD=1 1 3 -20O=64 16/12 WC=6.'6 DD=1 04 2Ð/ 12 WC=8.7 DD=1 1 4 22/12 8/12 e/ 12 31/12 WG=8.5 DD=1 I 7 I zs¡tz' WC=6.4 DD=l 1 6 IO t5 25 50 îEJJ I zz¡tz 10 f5 25 50 Lrl¡¡ltL I g LrJâ I ts¡tz I ts¡rz' WC=7.3 DD=1 1 2 l, ta¡tz l--LIt!l! I :Et-o-LIô 202A I t Fig, 2LOGS OF EXPLORATORY BORINGSH-PryßruMAR1 B-7- 1 39 LEGEND tJ TOPSOIL; URGANIC SILIY SANUY CLAY, l-lRM, MO|ST, UARK BR0WN. CLAY (CL); SILTY, SANDY, STIFF To VERY STIFF, SLIGHTLY MolST, EROWN. m SANN AND CI.AY LIGHT BROWN TO (sc-ct.); BROWN. SILTY,- MTDIUM DENSE, SLIGHTLY MOIST TO WET, F RELATIVËLY UNIIISIURBËD URIVE sAMPLË; 2-INCH LD. OALIFORNIA LINER SAMPLE 12712 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 12 BLOWS oF A 140-P0UND HAMMER.-,.- FALLING 50 INCHES WERE REQUIRED TO DRIVE THE CALIFORNIA OR SPT SAMPLER 12 INCHES. 4 oeprH To wÀTER LEVEL AND NUMBER oF DAys AFTER DRTLLTNo MEASUREMENT wAs MADE. --+-' OEPTH AT WHITH BORING CAVEI, FÚLLOWING URILIING. NOTE$ THE EXPLORATORY BORINGS WERE DRILLED ON FEBRUARY 1, 2O1B WITH A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. 2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVÀTIONS OF THE EXPLORATORY BORINGS WERE NOT MEASURED AND THE LOGS OF THE EXPLORATORY BORINGS ARE PLOTTED TO DEPTH. 4, THE EXPLORATORY BORING LOCATICINS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED: 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE APPROX¡MATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRÀNSITIONS MAY BE GRADUAL. 6. GROUNDWATER LEVEL 5HOWN ON THE LOG WAS MEA5URED AT THE TIME AND UNDER CONDITION5 INDICATED. FLUCTUATIONS IN THE WATER LEVEL MAY OCCUR WITH TIME. 7. LABORATORY TEST RESULTS; WC = WATER CONTEI.IT (%) (ASTM D 2?-16); DD = DRY DENSITY (PCT) (ASTU D 2216); _2QO= PERCENTAGE PÄSSING NO. 2OO SIEVE (ASTM D 1140). 1 I s 1 8-7- 1 3s LTGTl\ID AND NOTTS Fig, 3[d-Pryfl<U[\4AR SAIvIPLE OF: SillY Sand ond Clcr¡' FR0lvl: Boring 1 {ár 10' wc = 6.6 i4, DD z 104 pcf I 0 JJtrl > <n I z() tr ô =o U'z.o(J -l -¿ -3 -4 -5 i..t ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1.0 APPLIED PRESSURE _ KSF 10 SA|,IPLE OF: Silty Sond ond CloY FROlrl:Boring2|e.5' WC = ti,4 i'(, DD = 1i6 pcf rxf-'ANStor.l Lll.lDER Çol.lsTAl.ll PRËSSURE UFC)I.] V/ITTING f.O APPTIED PRESSURE - I(sF l0 t00 JJbJ =u) I z.o t-* tf, =() Øzo() 2 0 -l -2 -qfp I Fig, z!SWTLL_CONSOLIDATIOI! TEST RESULTSH-PryTi(JIVilAR18-7 -139 Hi*PryKlU[Ntllïi4u[ç* T¿\BLE N SLON'ÙN4Á\RV OF I.ABOR/ATORY T EST TRE$["'[.-T$ Project No. 18-7-139 DEPTH (ft) NATUR/tr1 MOISTURE CONTENf NATURAL ORY DENSITY PERCENl' PASSING NO.200 SfEVÊ UNCONFINED OOMPRËSS¡VE STRENGlHBORING (9;')(1r') SAMtrI F -_. -qB{DAI!qN.-''--- GRAVEL SAND , (1i)(pcf)IPSFI LIMIT (%\ INDEX to/"\ AfiERBERG LIMITS I LrourD pusrrc I SOIL TYPË (r. ¿í r).() ( 10 Silty Sand-r Cla.vr 13 10-.1 t Siltv Sald and Cla¡' j Sittv SanA and Cla1'15 ^.,i I l'+ I a 1IiIt i Si1¡'Sanci.v Clal' ll65ri. -l Silty Sanrl and Qlay i Silty Sand and Claya7.i30 i 1