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Home My WebLink AboutPreliminary Subsoil Study for Foundation Design 01.22.18H-PryKUMAR Geotechnical Engineering I Enginaering Geology Materials Testing | Ënvironmental 320 County Road 154 Glenw..d Springs, C0 81601 Phone: (970) 945-7988 Fax: (970) 94F8454 Email: hpkglenwood@kumarusa,com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado January 22,2018 Gianinetti Family, LLC Attn: Ernie Gianinetti 592 Cowen Drive Carbondale, Colorado 8L623 Prcject No. 17-7-879 Subject:Preliminary Subsoil Study for Foundation Design, Proposed Gianinetti Guest Ranch, North 8th Street, near Carbondale, Garfield County, Colorado Dear Ernie As requested, H-P/Kumar performed a subsoil study for design of foundations at the subject site. The sLucly was conducted in accordance with our agreement for geotechnical engineering services to Gianinetti Family, LLC dated December 79,2017. The data obtained and our recommendations based on the proposed construction and subsu¡face conditions encountered are presented in this report. Proposed Construction: The proposed construction will consist of a contmunity barn and nine cabins located on the property as shown on Figure 1. The buildings will likely be single story wood structures. Ground floors will probably be slab-on-grade at the community barn and structurally supported over crawlspace for the cabins. Cut depths are expected to range between about 2 to 3 feet. Foundation loadings for this type of constructlon are assumed to be relatively light ancl typical of the proposed tlpe of consüuction. If building conditions or foundation loadings are significantly different from those described abû\,e, we should be notified to re-evaluate the recommendations presented in this report. Site Conditions: The property is located northeast of Carbondale's 8th Street and adjacent the Roaring Fork River as shown on Figure 1. The terain is low lying and relatively flat, and has undergone some grading. The grading consists of apparent minor areas of shallow fill. The ground slope is slight and down to the west at grades of about ZVo. Elevation differencÊ across n the individual building sites is about 1 foot. Vegetation consists of grass and weeds. Po¡tions of tlre site neal the river are withil the 100 year' flood plain as noLed on the site plan provided to us and show on Figure 1. Subsidence Potential: The site and nearby areas of Carbondale are underlain by Pennsylvania Age Eagle Valley Evaporite bedrock. The evaporite contains gypsum deposits, Dissolution of the gypsum under certain conditions can cause sinkholes to develop and can produce areas of localized subside.nce. During previous work in the area, sinkholes were observed scattered in the Carbondale area. Sinkholes were not observed on the subject site, but grading may have covered them. Based on our present knowledge of the site, it cannot be said for certain that sinkholes will not develop. In our opinion, the risk of ground suhsidence at the Gianinetti Guôst Ranch site is low but the owner should be aware of the potential for sinkhole development. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating three shallow exploratory pits at the approximate locations shown on Figure l. The pits were excavated by the client. The logs of the pits are presented on Figure 2. The subsoils encountersd, below about I to lYzfeet oforganic topsoil or fill consisted ofreiatively dense, sandy gravel and cobbles. The gravel and cobbles were slightly silty af Pits 2 and 3 and extended down to the deplhs explored of 4 and 3 feet, and silty and slightly clayey at Pit 1 to a depth of 6 feet where the soils became slightly silty down to the pit depth of ? feet. The fill was encountered at Pit 2 and was apparent on site sandy gravei and cobble soils tt¡at appeared at least moderately compacted. Results of gradation analyses performed on disturbed bulk samples of the coarse granular soils (minus 5 to 6-inch fraction) obtained from the site are presented on Figure 4. The laboratory testing is summarized in Table 1. Free water was encountered in Pit I at the time of excavaticn at a depth of 5 feet. No free water was observed in Pits 2 and 3 at the time of excavation. The subsoils were slightly moist to moist, beccming wet below the groundwater ievel at Pit 1. Foundation Recommendations: Considering the subsoil conditions encounterrd in the exploratory pits and the natu¡e of the proposed construction, we recom¡nend spread footings placed entirely on the undisturbed natural coarse granular soils designed for an allowable bearing pressure of 2,500 psf for support of the proposed buildings. Footings should be a minimum width of 16 inches for continuous walls and 2 feet for columns. All fill, topsoil, and fine grained soils, and a1l loose disturbed materials encountered at the foundation bearing level within the H.P€KUIúAN Praject No. 17-7-879 -3- excavation should be removed and the footing bearing level extended down to the r¡ndisturbed natural coarse granular soils. Extcrior footings should be pruvided with ndequat€ cover above their bearing elevations for frost protection. Placetrent 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 tn span local annmalies stlch as by assuming an unsupported length of at least l0 feet. Founclation walls acting as retaining structures should also be designed to resist a laterai earth pressure based on an equivalent fluid unit weight of at least 50 pcf for the on-site granular soils, excluding topsoil and plus 6-inch size rocks, as backfili. Floor Slabs: The naturarl on-site coarse granular soils, exclusive of topsoil, are suitable to support lighlly loaded slab-on-grade construction. The suitability of the existing fill to support floor slabs should be furthe¡ evaluated at the time of construclion. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and coiumns with expansion joints which aliow unrestrained verticâl movement. Flso¡ slab contrcl joints should be ursed to reduce darnage 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 piaced beneath slabs for support and to facilitate d.rainage. This material should consist of minus 2 inch aggregate with less than 507o passing the No. 4 sieve and less than2To passing the No. 200 sieve. All fill materials for support of fioor slabs should be compacted to at least g1Vo af maximum standard Proctor density at a moisture content near optimum. Required fill can cansist of the on- site granular soils devoid of topsoil and oversized (plus 6 inch) rocks. Underdrain System: It is ou¡ understanding the finished floor elevations of the bulldings at their lowest levels is at ar above the surrounding grade. Therefore, a found.ation drain system is not required. Groundwater level at the site may rise during spring run-off. Frozen ground during spring runoff can also creaîe a perched condition. 'We recommend below-grade construction, such as retaining walls and basement a¡eas, be protected from wetting and hydrostafic pressure buildup by;rn underdrain and wall drain system. If the finished floor elevation of the proposed structures has a floar level below The surrounding grade, o¡ below grade crawlspace areas are planned, we should be contacted to provide H-P€KUtVlAR Projecl No. 17-7-879 -4- recommendations for an underdrain system. Ail eafih retaining structures should be properly drained. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the huilclings have been completed: 1) Intlndation of the foundation excavations and underslab areas should be avoicled during construction. 2) Exterior backfill should be adjusted to near optimum moisturê and compacted to at least 95Vo of the maximum standard Proctor density in pavement and slab areas and to at least 9A7o af the maxirnurn standard Proctor density in landscape areas. 3> The ground surface surrounding the exterior of the buildings shouid be sloped to drain away f¡om the foundation in all directions. We recommend a minimum slope of 6 inches in the first 10 feet in unpaved areas and a minimum slope of 2ilz inches in the first 10 feet in pavement and walkway areas. 4' Roof downspottts and drains should discharge well beyond the limits of all backfill. Limifations: 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 express or impliecl. The conclusions and recommendations sgbmitted in this report a¡e based upon the data obtained from the exploratory pits excavated at the locations indicated on Fig're 1 and to the depths shown on Figure 2, the proposed t5'pe of construction, and oLlr expcrience in the area' Our services do not include determining the presence, prevention or possibility of mold or other biological contaminanis (MOBC) developing in the future. If the client is concerned about MOBC, lhen a professionai in this special field of practice should be consulted. Our ûndings include interpolation and extrapolation of the subsurface conditions identified at the exploratory pits and variations in the subsurface conditions may not become evident until excaYation is performed. If condi¡ions encountered during construction âppeil d.ifferent from those described in this report, we should be notiher1 at once so re-evaluation of the recomnendations may be made. 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 prnvicle continued consuitation and field services during canstruction t6 review and monitor the implementation of our recommendations, and to verify that the recommendations H-P&KUfVIAR Prcject No. 17-7-879 5 have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We lecornmend on-site observation of excavations and tbundation be.aring strata and 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-Pt David A. Young, P ÞAY/kac attachments Figure i - Location of Exploriieory Pits Figure 2 - Logs of Exploratory Pits Figure 3 - Legend and Notes Figure 4 - G¡adation Test Results Table I - Summary of Laboratory Test Results cc:Boundaries Unlimited - Bruce Lewis M H-P*KUÍVIAR Prcrject No. 17-7-879 I l- i g z3 e riú d c PROPOS CABINS "t è' ) /\ qe za åq EDa ' -*:r* 9'I I ! I ) t¡fol+ ()z gg i { & Ê c*E I ¿ors ØUcå f- O ç ce d ngg Lc)C: ÕocãU6 ¡* e I I ( ríl Þ-Ft \* .t s n PÊOPOSEO COMMUNITY BÅRN j R9 Eq \\--,' I \ r/\\/ \ñ\brB Ji r{ , * t'á: ií$ ååv'I s 0qn APPROXIMATE SCALI_T[TÏ ó I! t/ l.; ,'.\ ã 5l.\ ø * %ç a & .: ç 9a PIT I ø {t ¡S (3 ffi e g ã t(} a 17 -7 -879 H.PryKUMAR LOCATIûN OT [XPLORATORY PITS Fig. 1 I P tï 6 PIT 2 EL. 61 1 6.5 P EL. tTl 6114'tL.n U 0 WC=38"5 DD=75 | +4=65 -i-200=7 F-LJ IJlL I-l*o- r¿l(¡ _l I _.t *4=85 - 200= 1 F.u l¡l lL Ilt-- U q 5 1u 10 17 -7 -879 H-PVKUMAR LCIGS OF EXPLORATORY PITS Fî9. 2 I € I ã LEGEND GRAVEL AND COBELES WET SELOW GROUNDWA HAND DRIVTN LINER SAMPLT DISTURBED BULK SAMPLE. _ DEPTH TO WATER LEVEL AT TIME OF PIT EXCAVATION T0PSOIL; HlGljLY ORGÄN|C StLTy CLAY, SOFT, V[ny MO|ST, BLACK FILL: MAN-PLÀCED SLIGHTLY SILTY SANDY GRAVËL AND COBBLES, MEDIUM DINSE, SLICHîLYMOIST, BROWN. l9Y .G_9)¡ SANDY, StLTy, si-tcHTly cLAyEy, DrNsE, M0|ST BEcoMtNGTER LEVEL, BROWN, ROUNDEÐ ROCKS. GRAVEL AND CCIBBLES^ (CM_GP), SANDY, SLIGHTLY SILTY, DENSE, MOIST TO WEî AT PIT 1,SROWN, ROUNDTD ROCKs. þ t, NCITES i. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON JANUARY 12, 2A18. 2' THE LOCATIONS OF THE IXPLORATORY PITS WERE MEASURED APPROXIMATELY SY PACING FROMFTATURES SHOWN ON THT SiTE PLAN PROVIDEO. 3. THE ELEVATIONS OF THE TXFLORATORY PITS WERE OSTAINED BY INTERPOLATION 8ETWEENCONTOURS ON THE SITE PLAN FROVIDED. 4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SHOULD SE CONSIDERED ACCURATE ONLYTO THE DEGRTE IMPLIED BY THE METHOD USEÐ. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRËSENT THEAPPR0XIMATI E0UNDARIES BETWTEN MATERTAL Typts ,ANÐ rse rnrñinioNî r'ìiî Br cRADUAL. 6. CROUNDWATER LEVELS SHOWN ON THE LOGS WTRË MEASUREÐ AT THE TIMT AND UNDERCONDITIONS INDICATIO. NO GROUNDWÁTER ENCOUNTERED IN PITS 2 AND 3, FLUCTUATIONS INTHE WATER LEVEL MAY OCCUR WITH TIME. LAÊORATORY TEST RTSULTS: WC = WATER CoNTENT (%) {ASTM D 2216); DÐ = DRY DtNslTY (pcr) (nsrv o zzta);+4 = pERCENTAGE RETATNED 0N NO. 4 S|ÊVE (ASTM D 422);-200 = ptRcfNTAGr pASStNc NO. 200 STEVE (ASTM O 11+ô¡ 7 17 -7 -879 H-PryKUMAR LTGTND AND NOTTS Fí9. 3 å I a ã roo 9û aü 10 ao 50 40 JO 20 to g o to ,0 30 ao åû 60 70 ao - F P 90 too DIAM CLAY TO SILT coSgLES GRÅVEL 65 7" SÁND 2A % LIQUIO LIMIT PIASIIC{TY INÐEX SAMPLE Of: SilTy Sondy Grovsl with Cobbt6 {FILL) SILT ÀNT CLAY 7 % FROM: Pil 2e0.5'-1.5 ¡ 10c to 30 70 5û ao 3ú 2E to û o t0 26 50 40 50 Gç ?o €0 90 ro0 ¡ DIÁMËTIR OF CLES 2.O LLIMETfRS r52 CLAY TC SILT COBBLES GRÁVEL A5 % SÅNÛ LIOUIO LIMIT SAMPLE 0F: Sondy Grcval oñd Cobbtß! l1 % PLASÏIC'TY INDTX FROlrt:Pit2O3-4' SILT AND CLÅY I Y" Th6r. t.!t rolulf! opply orly lo lhc!oñpl6¡ whlch ver? tasf.d. ThGtr!l¡ng ¡.porl rholl ñol bG ¡cF¡oduc¡d,lxc.pt lñ lull, w,lhout th. wriitrñoppmvg, ol Kumır ¡( A3coci6l6s. lnc.Sl.r. o¡oly!ís l.slín9 Js Þ.rlorm;d ¡n occo.do{cã vlth ASI},1 D,aZ?, ÂSt}.{ Ct36 and,/or Asltl Dl 1.10, u-9. HYDÊOMETER ÀNÀLYSIS 7 HAs sI[V[ ANALYSIS OPEXITGS : --"1-:::t:.---l---"::-r :-*l: :_+::.:::r:=t_l_---,+-::r: __..-_l: ::::1: -----J*::1.: --'1---r'r - r-l 2 l27l SAND IN GRÀVEL FINE MEDIUM lCOnnSr FINE çoAR5[ HYDROMETER ÀNALYSIS SIÊVE ANALYSIS 24 ilRs 7 iASa5 vrN ,l ù,N ßoúrN 1lÌÍ ÊtåDtNGS sERIES c!f,^i OPENIHGS SAND GRAVEL FINË MEOTUM jCoanse FiNE COARSE 17 -7 *879 H-PryKUMAR GRADATION TTST RTSULTS Fig.4 H-PNKUMARTABLE 1SUMMARY OF LABORATORY TEST RESULTSProject No. 1 7-7-879SOIL TYPESilty Clay (Topsoil)Silty Sandy Gravel rvithCobble (Fili)Sandy Gravels and CobblesUNCONFINEDCOMPRESSIVESTRENGTHfpsFlATTERBERG LIMITSPLASTICINDEX(ololLIQUIDLIMIT(%\PERCENTPASSINGNO.200SIEVË1GRADATIONSAND(%)2814GRAVEL(%)6485NATURALDRYDENSITYlncf)75NATURALMOISTURËCONTENT{%l30.8SAMPLE LOCATIONDEPTH{fttIVz- LV23-4PITI2