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Home My WebLink AboutSubsoil Study 05.23.2018H- Gsotachniöal Ëngìnoår¡ng Matedal*Testlng I Environmental 5020 County Road 154 Glenwood Springs, CO S1601 Phone: (gZ0) 945-Z9BS Fax: (970) g4S-84S4 Ëmail: hpkglenwood@kumarusa.com Office Locations:Denver iHQ), Parker, Colorado SBrings, Fort Collins, Glenwood Springs, Summit Count¡ Colorado ËUßS{}ãL STUDY FOR FOUF{ÐATION DESIGN FROPÛSEÐ RESIDENCE tûT 92,IRONBRTDGE 368 RIVÐRHEND W,4Y ç,åR,FT*Ã,Þ EÛÐNTY, CûLTRAÐÛ FROJ&Cr', ¡.{{}. 19"7-3tI M;lY 23,2û18 PITEPÂãIED FOR: REÐ DEER REALTY ATTN: LEO CARNNCHAEI, OlSl PRINCE ÐRIVE CARBONDALE' COLORADO 81623 tlsg*ã Ëepäael) TÅBÏ,E SF' {:{}Nrgr{T'$ PURPOSE AND SCOPE OF STUDY BACKGROUND INFORMATION PROPOSED CONSTRUCTION .. SITE CONDITIONS . SUBSIDENCE POTENTIAL.. FIETD EXPLORATION SUBSURFACE CONDMIONS FOUNDATTON BEARING CONDTTIONS DESIGN RECOMMENDATIONS FOUNDATIONS FOUNDATION AND RETAINING WALLS... FLOOR SLABS.......... UNDERDRAIN SYSTEM ....."...... SURFACE DRATNAGE LIMITATIONS FIGURE 1 . LO{:ATION OF EXPLORATORY BORINGS FTGURE 2 - LOG OF EXPLORATORY BORING FIGURE ¡ - SWNLI-CONSOLIÐATION TËST RESULTS FIGURE 4 - GRADATION TEST RESULTS TABLE 1- SUMMARY OF LABORATCIRY TEST RESULTS I 1 1 -3- ...-2 - ¿- 2- 3- 7- ..-4- -4- -5- -7 - H-Fezut$åR Project No. 18-7-318 Ptíq{P$sÐ ANt} scûFE {}F.' S3'[13]y This report prcsents the tesults of a subsoil study for a proposed residence to be located on Lot 92, Ironbridge, 368 River Bend Way, Garfield County, Colorado. The project site is shown on Figure 1. The purpose of the study was to develop recommendations for the foundation design. The studywas conducted in accordance with our agreement for geotechnical engineering services to Red Deer Reality daterl May 2, 2018. .{ ñeld explofation program ccnsisting of an exploratory boring was conducted to obtain informatisn on th* subsurface sonditia:rs. Sarnpies of the subsoils ohtained during the fietd exploration wer* tested:in the laboratory to determine their classificatian, cornpressibitity or swell ancl other engineeling characteristics. The results of the field exploration and laboratory testing vrere analyzed to develop rccommendations for foundation types, depths and allowable pressures for the proposed building founclation. This report sumrnarizes the clata obtained during this stud3l and presents our conclusions, clesign recommendations and other geotechnical engineering considerations based on the proposeel construction and the subsurface conditions encountered. $A{:KGR f}{JNÐ INT¡TRMATTON Hepworth-Parvlak Geoteehnical (now H-P/Kumar) previously perfarmed a preliminary geotechnical study in the subdivision which included the subject lot, rcpcrt dated December 31, 20t2,Job No. 101 196-1. Information from this report has been reviewed and considered in the preparation of this report. P&OF{}SED CONSTRTJCTI{}N The proposed residence will be'a one and two story siructure over crawlspace with a slab-on- grade garage. Cut depths are assutned to be between 3 to 5 fcet and foundations loadings are assumed to be light. If building lacation, grading or loading information changes, we should be notified to re-evaluate the recommendations presented in this report. H-P*KUfvlAÊ Projecl No. 18-7-318 -2 $êTã{ C{}Hg}Ë?'å{}H$ The lot was vaeant and the ground surface appeared mostly natural at the time of our field expiorati$n although there rvere scattercd cobbles inclicating p*ssible past grading. T'he terrain is slightly sioping down to the easf at a glade of about 3 to SVo in the building area fhen steepens to the north and east. Elevation difference âcross the building areas is about 4 feet. Vegetatio:r consists of scattered sage brush, grass and weeds. $E]*fðIÐSHCE F$TENTLqã" Bedrock of the Pennsylvanian age Eagle Valtey Evapcrite underliss the lronbridge SuSdivision. These rocks are a scquenee of gypsiferous shale, fine-grained sandstone ancl siltsrone with some massive bsds of gypsqm and limestone. There is a possibility that massive gypsui¡r deposits associated with the Eagle Valley Evaporite underlie portions of the lat. Dissofultion Õf the gypsum uncler eertain conclition.ç can cãLlse areas of localized suSsidence. Dgring previous work in the area, seveïal sinkholes were observed scatterecl throughout the trronbridge Subdivisiofl. These sinkholes appear sirnilar to others associated with the Eagle Valley Evaporite in other areas of the Raaring Fork River valley. Sinkholes were nût observed in the immediate area of the subject lal, No evidence af cavities was encountered in the subsurface materials; howevsr, the exploratory troring was rclatively shallow, for foundation design oniy. Based on our prcsent lurowledge af the subsurface conditions at the site, if cannot be said for certain that sinkholes will not develop. The ¡isk of fulure ground subsidence on Lot g2, thraughout the service life of the proposed st¡ucture, in our opinion, is low and similar to other platted lots in the a¡ea; however, the owner should be made aware of the potential for sinkhoåe development. If further investigaticn of possible cavities in the beclrock below the site is desired, we shauld be ccntacted. FXELT} EXPLGRATTSN The fielci exploration for the project was conducted on May 4, 2018. One explolatory boring was drilled at the loeation shown on Figure 1 to evaluate the subsurface canditi*ns. The boring was advanced with 4-inch diameter continuous flight arigers powered by a truck-mounted CME- 458 drill rig. The boring was logged by a represenrative of H-p/Kumar. Frojecl ño. 1å'7-318 -3 - Salnples of the subsails werc taken with 1% in*h and 2 inch LÐ. spocn samplers. The sa*rplers were driven into the subscils at valious depths with blows from a 140 pound hammer falling 3û inches. This test is similar to the standard penetlation rest deseijbed by ASTM Method D-15g6. The penetration resisfance values are ail indication of the relative density or consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on thÕ Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. $g ÐBs{Ie F3"CË C*,N*ã?.ã{}HS A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The sul¡soiis consist of about Vz foaT cf topsoil overlying 4r/z teetof ¡nedium stiff sandy silty clay, further overlying dense to very dense, slightly silty, sandy gravel and cobbles. DrÌ¡ing in the dense granular soils with al¡ger equipment was difficult due to the cobbles ancl prolrable boulders and drilling refusal was encountered in the deposit. I.aboratary testing performed on samples obtained from the boring included natural moisturc content and gradation analyses. Results of swell-consolidation testing performed 'n a relatively undisturbed drive sample, presented on Figure 4, indicate law to mcderate cornpressibility uncler loatling with a low callapse potential when wetted. Results of gradation analyses performed on a srnall diameter drive sample (minus lYz inch fraction) of the coarse grannlar s¡bsoils are shown on Figure 5. The laboratory testing is summarizçd in Table f . F{o free water was encountered iit the boring at the time of drilling and the subsoils were slightly maist. FûUgglATIûN BEr{RtrNG CtÞüÐIfI#f{S The fine-grained clay soils possess low bearing capacity and low to moderate settlement peitential. Tlhe underlying coarse granular, sandy gravel and cobble soils possess moclerale bearing capacity anel relatively low settlement peitential. H-Pæ¡ç¡¡Y¡¡qg Projeet No. 18,7-31ð -4 At assnmed excavation depths, the subgrade could transition the clay anrf eoars* granular soils Spread footings bearing entirely on the coår:se granular soils are recommendecl for foundation slrppott of the residence to limit settlement potenfial. Ðgstr#N REC{}1þ{MËHÐ.&ï'[ûHS FOUNDATIONS Considering the subsurface conditions enccnntered in the exploratory boring and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural gmnular sails or compacted structural fìil. The design and construction criteria presonted below should be obsefl/ed for a spread footing foundation system. 1) Footings placed on the undistulbed natural granular soils or compacfed structural fill should i:e designed for an allowable bearing plessure of 2,500 psf. Based on experience, we expect settlement of footings clesigned and constructed as discussed in this section ç,ill be about 1 inch or less. 2) The footings should have a minimum width of 16 inches for continuous walls and 2 feet for isolated pads. 3) Exterior footings and foatings beneath unheated areas shor¡ld be provicled with adequate soil cover above their bearing elevation for frost protection. placement of foundations at least 36 inches below exterior grade is typically usect in this areâ. 4) Continuous foundatian walls shonld be reinforced top and bottam to span local anomalies such as by assuming an un,crlpported length of at least l2 feet. Foundation walls aeting as retaining structures should also be designed to resist lateral earth prtssures as diseussed in the "Foundation and R.etaining Walls" seetion of this rÊpoÉ. 5) Any existing fill, topsoil, clay an<l loose or disturbed soils should be remaved and the footing bearing level extended down to the relatively dense natural granular soils. The exposed soils in fcoting area should then be moistened anel cornpaeted. Structural fill placed to reestablish design trearing ievel should consist of a Project Nû. 18-7-318 -5- relatively well graded granular soil crimpactecÌ ta at lcast g87o afstandard Froctor density at near optimllm moisture coiltent. A representative of the geotechnical engineer should observe all footing excavations prioÍ to çonffete placernent to evaluate bearing ccnditions. FOUNDATION AND RETAININÛ S/ALLS Founclation walls and retaining str¡Jctures which are laterally suppolted and can tre expected to unclergo only a slight åmount of deflection should be designed for a lateral eafih pressure computed on the basis of an equivalenrflilid unit weight of at least 5* pcf for backfill consistinig cf the on-site soils. Cantilevered retaining structures r¡¡hich are separate from the residence and can be expected Éc deflect sufficiently to mobilize the full active earth prcssure condition shauld be designed for a lateral earth pressure computed an the basis of an equivalent fluid unit weight ofat least 45 pcf forbackfill consisting ofthe on-site soils. Ail foundation and retaining structures should be designeci for appropriate hydrostatic and surcharge pressurcs such as adjacent footings, traffic, canstruction materials and equipment. The pressures recomrnended above assume drained conclitions betrind the walis and a horizantal backfill surface. The buildup of watel behind a wall or ân upwÍlrd sloping backfîll surface wiil inçrease the lateral pressure imposed cn a foundation wail or retaining structure. An 'nderdrain should be provided to provent hydrostatic pressure buildup behind walls. Backfiil should be placed in uniform lifts and compacted ta at ìeast gt% af the rnaximuni standard Proctor density at a moisture content at or slightly above rptimurn. Backfill placed in pävement and walkway areas shoulcl bo conrpacted to at Least 95Va of the ma-''rimum standard Froctor density. Care should be taken not to ovÐreompact the backfill or use large equipment near the wali, since this cauld cause excessive lateral pressure on the wall. Some settlement of deep foundation wall backfîll should be expected, even if the material is plaeed coriectly, and could result in distress ta facilities canstrueted an the bnekfill. Backfill shauld nct contain crganics, debris or rock larger than about 6 inches. 6) H.P*KUMAR Frojsct No. 1B-7-31ã -6- The lateral t*sistanee of foundation qrr retaining wall f*otings will t¡e a *ombinaTian,of the slirìing tesisfance of the footing on the fonnclation materials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of the footings can be ealculated based on a coefficient of fricticn of 0.45. Passive pressure of compactecl backfill against the sides of the footings ean be calculated using an equivalent fluid unit weight of 350 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strength. Suitable faetors of safety should be included in the design to iimit the strain which will ûüeur at the ultimate strength, partieularly in the case of passive resistance. Fill placed against the sides of the footings to resist iateral loads should be compacted to at least g|Vo of tlte maximum standard Frocto:"density at * noisturc content near optimum. FLÛOR SL,{BS The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade constructicn. To reduce the effects of some diffetential movement, tloor slabs sho¡ld be separated ticm all bearing walls anel colnmns with expansion joints which allow unrestrained vertical mûvement. Floor slab conhol joints should be used to recluce damage due ta shrinkage eracking. The requirements far joint spacing and slab reinforcement should be established by the designer based cn experienee and the intended slab use. A rninimum 4 inch iayer of rciatively well graded sand and gravel such as road base should be placed beneath slabs fcr support. This material should consist of minus 2 inch aggregate with at least 5û7o retained on the No. 4 sieve and less than lZ%a passing the No. 20û sieve. A1l fill materiais fot' support of floor slabs should be compacted to at least g|Ta af m¿ximum standard Proctor density at a moisture content near optimum. Requir*d fill can consist of the on- site soils devoid ofvegetation, topsoil and oversized rock. UNT}ERDRAIN SYSTEM It i.s aur understanding the proposed finished floor elevation at the lorvest l*vei is at or abovc the surrounding grade and the crawlspace will be relatively shallow, around 3 feet deep. Therefore, a foundation drain system is not required. It has been our experience in the area that local H,PÐI{J|V&AR ProjecT Nn. 18-7-318 -t- perched g¡oundw¡rtsr can develop during tímes of heavy precipitation ûr :iÕasûnal runetff. Froe** ground cluring spring runoff can crÊate a perchecl condition. l#e recommend below-grade construction, such as retaining walls and basement areas, be protected fram wetting and hydrostatic pressute buildup by an underdrain and wall drain system. If the finished floor elevation of the proposed structure is revised to have a floor level below the surrounding grade, we should be contacted to provide recornmendations for an underdrain system. All eafth retaining structures should be properiy drained. SURFACË DRAII{A*g The following drainage precautions should be observed during construction and maintained at all tir¡es after the residence has treen completed: 1) Ïnundation ofthe foundation excavaticns and underslab areas should be avoided duríng constmction. 2) Êxterior backfiil shor¡ld be adjusted to near optimum moisture and compacted to at least 95Va of the maximurn standard Proctor density in pavement and slatr arcas and to at least 9t7o of the maximurn standard Proctor density in landscapð aïeas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from tire faundatian in all directions. We rsccmmend a minimum slope of 12 inches in the first 1û feet in un¡raved areäs and a minimu¡n siope af 3 inches in the first 1û feet in paved areas. 4) Roof downspouts and drains shouid discharge well beyond the limits of all backfill. 5) Landscaping which rcquires regular heavy iruigation should be located ar least 5 feet from foundation walls. [,IMITÂTTÛNS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area at this time" We make no vuarranty either express or implied The conclusions and recommendations sub¡nitted in this report are based upon the data obtained H-pv{uMÄ* Project No. 1å-7-318 e from the exploratory boring drilled at the location imlicated on lìigur* 1, the proposed type of construction and our experience in the area. #ur services do not include determining the pressnce, prevention or possibility af mold or other biological contaminants (MCÌtsC) developing in the future. If the client is concerned about MOB[:, then a professional in this special field of practice should be consulted. CIur findings include interpolation and extrapolation of the subsudace conditions identified at the exploratory borÌng and variations in the subsurface conditions mây not become evident until excavation is performed. If conditions encountered during construction âppear different from those describecl in this report, we shauld be notified so that re-evaluation of the recommendations may be rnade. This report has been prepar"ed for the exclusive use by our client for design purposes. 'W'e are not responsible for technical intelprctatíons by others of cur ínformatian. As the project evûlves, îve should provide cÕntinuÊd eonsultation and field services during ccnstructisn to review and monitar the impiemsntation of our recommendations, and to verify fhat the recom¡nenclations have teen appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommenrl on-site observation of exeavations and foundation bearing strata and testing of strnetural fill by a lepresentative of the geotechnical engineer. Respectfully Submimed. H-F+ KUMAR James H. Parsons E.L Reviewed by: Steven L. Pawlak P.Ë. JHP/kac Cc: Jeff Jahnson A¡chitectural * Jeff Johnson {jjAggbggglæt} H-PEKUMAF Projecl No. 18-7"318 i {rl ql Ë*RåruG 1 i rå -.ì r1i €') ,r*! tr4 -. r1J ìt 6iã6 P¡rft *Lari 3,1 LESEhIÞ ¡ O BORINC FOR CURRÊNT STUÐY ÊOÊING FOR PREVITUS STUDY(HF GEOTECH JOB NO. 101 1e6-1) APPROXIMATE SCALE-FETT 1 8-7*51 I H-PryKUMAR LOCATION OF TXPLORÂTORY BORINGS Fig. 'l Iã *¡ stRr¡Jü 1 LEGENq- ffi TOFSûIL: SÀNÞY CLAY åilD SILT, SL¡G$TIY þ{0tSI, SRüt{¡¡. SÂl'lÐY CLÀY (01): SILTY, ME0|UM ST|FË, SLtûHfLy MOIST, 3R0WN. 0 !^- l^¡J Ld¡r- I:r û- l¿lô 11 /12 WC=4.9 DD=95 -200=55 r4=52 -200=1 1 13 bA i I 43/6,50/5 WC='1.9 GRÅVEL AI'¡D COEBLES VTNY OENS€, SLIcHTLY (GM*0P)i SL|GHTLY StLTy, sÄNDy, DENSÊ T0 MOIST, BROI¡/N, ROUNDEO ROCK,5 10 ORIVE SAMFLE, z-INCH I.O. CALIFORNIÂ LINER SÂMPLr. DR|VE SAI,|PLE, r 5/8*|NCH t.0. SpLtT Sp00N sIÂr{DÅRD PÊNETRATION TEST, 11712 DRtVt SAMPLE 8L0W C0UNT. tNDtcATeS IHÂT 1l 8t_0\4's 0F A",,- T4O-POUNÛ HAMMEA FÂLUNG 3O II.¡CHES WTRE RIQUIRED TO DRIVE ,THË SÀMPLËR '2 INCHES. f ,rnacrrcnl AUGTR REFusÂL : NOIES I. THT ËXPLORATORY BORING WÅS DRILLED ON MAY 4, 2OI8 WTH Â 4_INCH DIAMETTR CONTINUOUS FLIûHT POWEft AUûER. 2. THT LOCÅTIOH OF THE EXPLORAIORY BORING WAS MEASURED APFROXIMAÍELY BY PÅCING FROM FEATURES SHOYIIN ON THË SIÎE PLAN PROVITTD. 3. THE ELEVAIION OF TI{T EXPLORATORY BORING WAS NOT MIASURTI) ÂNÐ THT LOG OT THE EXPLORATORY EORING IS PLONEO TO OEPTH. 4. THE EXPLORATORY BORING LOCATION SHOULÐ BE EOf,ISiDTÊED ACCURATE OI¡LY TO THE OTGRTT IMPTIED BY THT METHOD USÊo, 5. THË TINES BETWEËN MATERIALS SHOWN O}I THE EI(PLORATORY SORING LOG RTPRESENT THE ÁPPROXIMATE BOU¡¡ÛANIES SETWTTN MATTRIAL TYPES ANO THE TRÁNSITIONS MÄY BE CRÄOUAL. 6.TRÕUNDWATER WAS NOI TNCOUNTTRÉD IN THE BORING AT THT TÍME OF DRILLING. 7. LÂBORÂTORY TËST RESULTS; WC = WATTR CONTËNT (X) (ÂSTM D 2216); OD : DRY DENSITY (PCr) {ASTM O 2216); +4 = PERCENTAGT RETAINEO ON NO. 4 SIEVE (ÀSTII D 422)i -2f)0 = PEROENTAGI PAsstNô N0. 100 StEvE (ÁSTM D il40). 1 8-7-31 I H-PæKUMAR LCIG OF TXPLORATORY BORING Fig. 2 SAMPLE OF: Sondy Sílty Cloy FROM;Boring1€2.5' WC = 4.9 %, DD = 95 pcf -200 = 55 % ¡ 1 j I AÐDITIOF¡AL COMPRESSION UNDER CONSTA$T PRESSURE DUE TÛ WETTING I i ! : l l ì ..1 ! , T 0 àe JJl¡ =Ø I zoç ê Jo anzo() *1 4 -J -4 -5 *g ¡f I I H-PryKUIVIAR I I SWTLL-CONSOLIDATION TTST RTSULTS1 8*7*51 I Fig. 3 ro0 *û I 70 l0 lo 30 ó*¡o ã lso H ú Ef s 6g ,o ta o too ðLAY TO SÍLT EOËBLES TRAVEL ã2 16 SAND 37 X SILI AHD CI.AY 11 X SAMPLE OF: Sllghlly Sllly Sandy Grovel FROM: Borlng 1 t! 5' Thor! Irrl r.tultl opÞly only lo lhtlmplr¡ rhlch fd. l.rbd, fh.l.rllñg þpcrt rholl ñol b! rÇÞ¡odsard,rrcôpl lñ tull, wlthoul th. wr4ilêñogprwol of fsñsr t ^uoolola¡i tnE.Sræ. orctyd! l.rrlñâ la Þadom.d l^qccordaæ. elth ASIX 0a22, ASII¡ Ct30 oñd,/ðr ASTM 0ff40, HYÊfiOMË1ER AiIALYâIS IUÊ AerONôS ËlËvË ÁNALVSIS CLfÁÊ 38UÁRE -".--.,!. .- . : +.-¿'.--- L.."t-.^---.-."l-t-- - -.-.v.-..-.' - :-;fs:r__:_ '-t-"-!..--^--'- ì- -t - 1 - -- - .1.-.. j: .:+,:.i*l . -----Ë --'--"--. -,,".1---.-."-----t- -.. -i* -l;"r"-*-.*- -ç -*--- r'ì+-' .-.,._.,.. .- -¡_, --'--$_** --f --'-* ---,t^ .--, .-. - -,.-. -, *i*- . ..--. - SANO GRAVEL FINE MEDIUM lCOrnSe rINË toARSg 1 B-7-31 I H-PryKUMAR GRADATION TTST RTSULTS Fig. 4 H.P+KUMARTABI-H 1SUNñNiARV OF LABÕRATORY TË$T RES{JI.TSProject t{o" 18-7-318SOILTYPESandy Silty ClaySlightly Silty Sandy GraveiUNCONFINEDcot¡tPREsstvESTRENGTHfnsfltG l-tÍñtTsPt AST|CINT}EXPlo'lATÍERBFLIQUIDLIMITlø/o\PERCgNTPASSINGNO.200stEvÉ55t1GRASATIONSANO{%}GRAVËI.lvi!9552!{ATURAI-ORYOEfìlSlTY{ocflNATURALMOISTTJRECONTENTlo/ol4.91.9SAMPLEDEPTfrIffrì) t/.5SORING1