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HomeMy WebLinkAboutSubsoil StudyH-PVKUMAR Gaotecånlcål Englneerlng I Englneerlng Geology Materlals Testing I Envlrcnmental 5020 County Road 154 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 FOUNDATTON DESIGN PROPOSËD RESIDDNCE LOT Ell, FILING I, ASPEN GLEN 77 PUMA DRIVE GARITTELD COUNTY, COLORADO JOB NO. t?-7-24t APRIL I4,2OT7 PRBPARED FOR: ERIK CAVARRA P.O. BOX 6398 sNowMAss VILLAGn, COLORADO 816rs f ec av arra @ al n ineprope rt.v. co mi TABLE OF CONTENTS PURPCISE AND SCOPE OF STUDY ............... ...... . I - PROPOSED CONSTRUCTION SITE CONDITTONS SUBSIDENCE POTENTIAL. FTELD EXPLORATION SUBSURFACE CONDITTONS DESIGN RECOMMENDATIONS ............. FOUNDATTONS. FOUNDATION AND RETAININC WALLS FLOOR SLABS UNDERDRAIN SYSTEM SURFACE DRAINAGE ...... LTMITATIONS FTGURE I - LOCATTON OF EXPLORATORY BORINCS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURE 4 - GRADAT'ION TEST RESULTS TABLE I. SUMMARY OF LABORATORY TEST RESULTS )- -2- -3 - 3 3 4 5 6 6 -7 H-Prfg¡y1¡p ProJect No. 17-7-247 PURPOSB AND SCOPE OF STUDY Tltis report presents the results of a subsoil .study for a proposed residence to be located at Lot E I l, Filing I , Aspen Glen, 77 Puma Drive, Garfield County, Colorado. The project site is shown on Figure l. The purpose of the study rvas to develop recommendations for the foundation design. The study was conducted in accordance with our âgreement for geotechnical engineering services to Erik Cavarra dated March 21,7Afi . Chen-Northern, Inc. previously conducted a preliminary geotechnical engineering study for the subdivision development and reported the findings Dece¡nber 2A,1991, Job No. 4 l12 92 and a geotechnical study for preliminary plat design report dated May 28, 1993, Job No. 4 11292. A ficld exploration progrilm consisl.ing of exploratory borings rvas conducted to obtain inforrnation on the subsurface conditions. Sanrples of the subsoils obtained during the fìeld exploration were tested in the l¿lboratory to dete rmine their classi[ication, and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed ro develop recommendations for foundation types, dcpths and allorvable pressures for the proposed building foundation. 'l'his report surnmarizes the data obtained during this study and presents our conclusions, de.sign recommendations and other geotechnical engineering con.siderations based on the proposed construction and the,çubsurface conditions encountered. PROPOSED CONSTRUCTION At the time of our study, design plans for the residence had not been developed. The building is proposecl in the area roughly betrveen the explorutory boring locations shorvn on Figure l. We assume excavalion for the building will have a maximum cut depth of one level, about l0 fect below the existing ground surface. For the purpo$e of our analysis, foundation loadings for the structure were ûssurned to be relatively light and typical of the proposed type of construction. If building loadings, location or grading plans change signif icantly from those described above, we should be notifìed to re-evaluflte the reco¡nmendations contained in this rcport. H.P..KUMAR Project No. 17-7-247 -2- SITE CONDITTONS The property is vacant of structures and vegetated rvith grass and weeds. The ground surface i.s relatively flat with a slight slope down to the rvest. An irrigation dirch is located along the north and rvesl propcrty lines. SUBSTDENCE POTB,NTIAL Beclrock of the Pennsylvnnian Age Eagle Valley Evaporite underlie.s the lower Roaring Fork Valley and the Aspen Glen subdivision. These rocks are ¿l sequence of gypsiferious shale, fine- grained sandstone/siltstone and limestone rvith some nrassive beds of gypsum. There is a pos.sibility that mass¡ve gypsum deposits associated rvith the Eagle Valley Evaoprite underlic portions of the property. Dissolution of the gyp.sum under certain conditions can cause sinkholes to develop and can produce areas of localized subsidence. During previous work in the area, several broad subsidence areas and sinkholes were observert scattered throughout the Aspen Gten sttbdivision (Chen-Northern, Inc. l99l). These sinkholes appear simitar to others associated with the Eagle Valley Evaporire in areas of the Roaring Fork Valley. The site is mapped as lying just outside to the rvest of a broad surface depression area ¿rnd about 300 feet southwest of a mapped sinklrole, No evidence of subsidence or sinkholes rvas observerJ on the property or encountered in the subsurface materials, holever, the exploratory borings wcre relatively shallow, for foundation design only. Based on our present knorvledge of the subsurfuce conditions ut thc sitc, it can not bc said for certain that sinklroles will nut tlevelop. The risk of future ground sub.sidence at the site throughout the service life of the structurc, in or¡r opinion is low, howe ver the orvner shoukl be arvare of the potential for sinkhole development. If further investigation ol'possible cavities in the bedrock below the site is desired, we should be contacled. FIELD IIXPLORATTON The field explorotion for the project was conducted on April 3,2017. Tlrree exploratory borings wcre drilled at the locations.shown on Figure I to evaluate the subsurface conditions. The borings were aclvanced with 4 inch diameter continucus flight augers powered by a rruck- mounted CME-458 drill rig. The borings were logged by a representâtive of ll-P/Kumar. H-P*KUMAR Project No. 17-7-247 -3- Samples of the.subsoils were taken with l% inch and 2 inch I.D. spoon samplers, The samplers were driven into the subsoil.s at various depths rvith blows from a 140 pound hanlmer falling 30 inches. This test is similar to the standard penetration test describcd by ASTM Method D-1586. The pcnetration resistance values are an indication of the relative density or consistency of the subsoils. Depths at which the sarnples werc taken and the penetration resistance values are shown on f.he Logs of Exploratory Borings, Figure 2. The samples were returned to or¡r laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shorvn on Figure 2. The subsoils consist of about ó inche.s of topsoil overlying den.se, silty .sandy gravel with cobbles ancJ boulders. Drilling in the dense granular soils rvith auger equipnrent rvas difficulr due ro the cobbles and boulders which linrited the practical depth of drilling. Laboratory testing performed on samples obtained from the borings included natural moisture content and gradation analyses. Results of gradation analyses perlormed on .small diameter drive samples (nrinus lYz inch fraction) of the coarse granular subsoil.s are shorvn on Figure 4. The laboratory testing is sun¡marized in Table l. No free watcttvas encountered in the borings al the time of drillinglnd the subsoils rvere slightly moist to moist. DESIGN RACOMMENDAÎIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nüture of the proposed constnlction, we recommend the building be founded rvitlr spread footings bearing on the natural granular.soils. The design and construction criteria presented below should be observed for a spread footing foundation system. H.P+KUMAR Project No. 17-7-247 -4, r)Footings placed on the undi.çturbed natural granular soils should be designed fcrr an allowable hearing pressure of 3,000 psf. Based on expericnce, tve expect settlement of footings designed and constructed as discussed in this section will be abor¡t I inch or less. The footing.s should have a ¡nini¡num width of l6 inches for continuous walts and 2 feet for isolated pad.s. 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 exterior grade is typically used in this area. Continuous foundation rvalls should be reinforced top and bottonr to span local anomalies such as by assuming an unsupported lcngth of ar least l0 feet. Foundation rvalls acting as retaining structures should also be designed to resist lateralearth pressures as discussed in the "Foundation and Retaining Walls" section of this report. All existing fill, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the relatively dense natural granular soils. The exposed soils in footing area should then be moistened and compacted. Voids crented hy boulder removal should be backfilled rvith compacted sand and gravel or with concrete. A represent¿tive of the geotechnical engineer should observe all footing excavations prior to concrete placenrent to evaluate bearing conditions. 3) 4) 5) 6) FOUNDATION AND RETAINING WALLS Foundation walls and retaining structures rvhich rre laterally supported and can be expected to undcrgo only a slight amount of deflection slrould be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of al least 45 pcf for backfîll consisting of the on-site granular soils. Cantilevered retaining structures rvhich are sepârate fronl the residence and can be expectecl to deflect sufficiently to mobilize the full active earth pressure condition should be designcd fcr a lateral earth pressure computed on the basis of an equivnlent fluid unit wcight of at lcast 40 pcf for backfill consisting of thc on-site granular soils. Backfìll should not contain orgnnics or rock larger than about 6 inches. 2' H.P\KUMAR Proiect No. 17-7-247 -5- All foundution and retaining structures should be designed for appropriate hydrostatic anct surcharge pressures such as adjacent footings, traffic, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal hackfill surface. The buildup of rvater behind a wall or an upward sloping backfill surface will increase the lateral pressure imposed on a foundation wall or retaining structure. An underdrain should be provided to prevent hydrostatic pressure builclup behind walls. Backf¡ll should be placed in uniform lifts and compacted to at least 90Vo of rhe maximum standard Proctor density at a moisture content near optimum. Backfill placed in pavement and rvalkway areas should be compacted to at least 95Vo of tlrc maximum standard Proctor density. Care should be taken not to overcompact the backfill or u.se large equip¡nent near the rvall, since this could cause excessive lateral pressure on the rvall. Some settlement of deep founclation rvall backfill should be expected, even if the material is placed correctly, and could re.sult in dist¡'ess to facilities constructed on the backfill. The lateral resistance of foundation or retaining wall footing.s will be a combination of the sliding resistance of the footing on the foundation m¡lterials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of the footings can be calculared based on a coefficient of friction of 0.50. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalenl lluid unit weight of 400 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strenglh. Suitable factors of safety should be included in the design to limit the strain which will occur at the ultimate strength, particul¿¡rly in the case of pa.ssive resistunce. Fill placed against the sides of the footings to resist lateral load.s should be a granular material conrpacted to at least 95Vo of the maximum standard Proctor density at a moisture content ne¿¡r optimum. FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade construction. To reduce the effects of some diffcrential movement, floor slabs should be separated fro¡n all bearing walls and columns with expansion joints which allow unrestrainecl vertical movenlent. Floor slab controljoints should be used to reduce damage due to shrinkoge cracking. The requirements for joint spacing and slab reinforcenrent should be established b y the H.P*KUMAR Projecl No. 17-7-247 -6- designer based on experience and the intended slab use. A mini¡nunr 4 inclr layer of free- draining gravel should be placed bencath basement level slabs to facilitate drainage. Thi.s material should consist of minus 2 inch âggregate rvith at least 507o ¡etained on the No. 4 sieve and less than 2Vo passing the No. 200 sieve. All lill ¡naterials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a moisture content near optimurn. Required fill can consist of the on- site granular soils devoid of vegetation, topsoil and oversized rock. UNDERDRAIN SYSTEM Although free water was not encountered during our exploration, it has been our expericncc in the area that local perched groundrvater can develop during times of heavy precipitation or .seasonal runoff. Frozen ground dr.rring spling nrnoff can creâte a perched condition. tvVe recommencl below-grade construction, such as retaining walls, crawlspace and basement ¿lreas, be protectecl I'rom wetting and hydrostiltic pressure buildup by an underdrain.systenr. The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free-draining granular material. The drain should be placed ar each level of excavation nnd at least I foot below lorvest adjacent finish grade nnd sloped at a mininrunr lgo to a suitable gravity outlet, surrrp and punlp or dryrvell. Free*draining granular nr¿terial used in the underdrain system should contain less than 27o passing the No. 200 sieve, less than 507o passing the No. 4 sieve and ltave a nraximum size of 2 inches. The drain gruvel backfill should bc at lcast l% feet deep. SURFACE DRAINACE The following drainage precautions should be observed during construction and maintained at all ti¡nes after the residence has been completed: l) Inundution of thc foundation excâvation$ and under.slab areas should be avoidecl during construction. H-P.KUMAR Proiect No. 17-7-247 -7 - 3) Exterior backfill should be adjusted to near optinrum moisture ancl compacted ro at least 95Vo ol the ntaxintum standard Proctor density in pavement and slab areas and to at least 9070 of the maximum standard Proctor density in landscape ¿rreas. The ground surface surrounding the exterior of the building should be sloped to drain away from the for¡ndation in all directions. we recommend a minimum slope of 6 inches in the first l0 feet in unpaved areas and a minimum slope of 3 inches in the first l0 feet in paved areas. Free-draining wall backfill.should be covered with filter fabric and capped rvith about 2 feet of the on-site finer graded soils to reduce surface water infiltration. Roof dorvnspouts and drains should discharge well beyoncl the limits ol'all backÍ'ill. Landscaping which tequires regular heavy irrigation should be located at least 5 feet fronr foundation walls. 4) s) LIMITATIONS This study has been conducted in accordance with generally accepted geotechnicalengineering principles and prnctices in this ârea at this time. We nrake no warranty either express or implied. The conclusion.s ancl recontmendations submitted in this report are based upon the data obtained from the exploratory borings drilled at the locations indicated on Figure l, rhe proposed type of construction and our experience in the area. Our services do not include determining the presence, prevention or possibility ol'nrold or other biological cont¿tm¡nants (MOBC) developing in the future. If the client is concerned about MOBC, then a professional in this special field of prâct¡ce should be consulted. Our findings include interpolation and extrapolntion of thc subsurface conditions identified at the explor¿¡tory borings and variations in the subsurface conditions may not become evident until excavation is performecl. If conditions encounterecl during con.struction appear different from those described in this report, rve should be notilied so that re-evalualion of the recommendat¡ons may be mnde. This report has been prepared for the exclusive use by our client for design purposes. We are not responsible for lechnical interpretations by others of our infarntation. As the project evolves, we should provide continued consultation and field services during consfruction to review and monitor the implementâtion of our recommcndations, and to veri fy that the recommendations 2\ H-P\KUMAR Project No. 17-7-247 8- havc becn appropriately interpreted. Significunt design changes mäy requ¡re additional nnalysis or nlodifications to the reconrmendation.s presenled herein. lVe recommend on-site observntir.¡n of excavations and foundation bearing strata and testing of structuri¡l fill by i¡ representotivc of the geotechnical enginecr. Respectfully S ubmitted, H-P* Louis E. Eller Reviewed by: Èjj Rt¡l !.¡ !:r t e Steven L. Pawlak, P.E 15222. LEE/kac a a a REFERENCES Chen-Northefn,lnc., 1991, Frelitnínur¡,Gcotedmìntl htginccring,llrrr/¡', Prapasad Aspen Glut Ðevclopueul, Gurficltl County, Colorado. Prepared for Aspen Glen Company, clated December 20, 1991, Job No. 4 11292. Chen-Northern, Inc., 1993. Geotecluúu¡l Engineering Snd¡,for Prelinúnnr¡'Pltrî Desígn, Aspcrt GIen l)evelopnrc,fl, Gatficlcl Corurfy, Colarçt{o. Prepared for Aspen Clen Company, dated May 28, 1993, Job No. 4 11292. H-Pi,çg¡Y¡P Projecl No. 17-7-247 t{-nçJ'E)G4-$'&¿.Vît!tv, te6ÐrF4 {lqy-ff,çi¿-?\,9',¿\¡affidm¿ Ílftrn ?t&ur.¿A *tE nro!lo.szsI.t¿tottoúpg-t8wñd/rr¿4!rn toøoqq {tmnllIt-CNo(t¡Cû(,,ç¿,gtÊN9'^?'a- mttÌtcGErrlÞ.t1tãox=Itlv,c,frIl1mFIo¡&tTDonG'\#\\t\l.ne!,€ilrn.gtr,ÒtstÐdIIIIIII¡II¡IIt"\.92o()?,6)3rt{,,-%49 ûo1 rvvz?^)4 a? gîo,= tJ bs ¿9Í's¿Gr /Ly rôrN!I!IN'5!-.LI-u¿¿-/\-(-Þno(ì{oo'41rflX-þt-c)-{OÐolo¡,C,utal(O BOßING 1 EL. 6066.5'ÊORING 2 SORING 3 EL. 6065'6070 EL.6065.5 6070- 6065 6065 50/5 56/12 WC=2.4 *4=55 -200=9 so/s 30/ t2 WC=5.8 *4=49 -200= I 0 6060 5a/5 6060 3t /12 67 /12 6055 605s5e/3 sa/2 6050 6050 r, 17-7-247 H-PTKUIVIAR LOGS OF EXPLORATORY BORINGS Fig. 2 LEGEND ffirorsorr; oRGANlc sANDy cLAy AND srLT, F'RM, 'LTGHTLy MorsT, DARK REDDT'H BRowN.N ffinatïti,Egitåffi-âilt-Bflib?ã-t-of1-oul' sANDy, srLTy, DEN'E To vERy 'EN'E, sLrcHTLy I ! RELATTvELy uNDTsTURBEo ÐRrvE sAMpLE; 2_INCH r.D. cALTFoRNTA LINER sAMpLE. I gxilå,.¡^Tgifi' ;rîuBâRD pENETRAîroN TEsr (spr), r 3/B rNcH r.D. splrï spooN 56/tz Pflii'åtfiÍ,.?,"'*'Ê?E-hJü?itå'iå 'JliJ,',ïF'3i;,3å*å tfi?ï!ÍrFf#ii ,NcHEs. ,NOTESr' ¿äitï^iüå3!^li'lïtt?lilH ï,ïåF-:RTLLED oN APR,L s' z0r7 wrr' A 4-rNcH DTAMETER 2. THE LOCATIONS O^I THE EXPLORATORY BO.RINGS WERE MEASURED APPROXIMATELY BY PACINGFR.M FEATURES sHow* oru rHÈ srib prÁFr ÞñoüröÈı."'-^ 3' ¿Bi,tåb'*tjiîi?r?t r||rt f,fr*ff$ßl'BoRrNcs WERE oBTATNED By rNïERpoLAroN BETgÊEN 4. THE EXPLORATOII BORING LOCATIONS-A.ND_ELEVATIONS SHOULD BE CONSIOEREO ACCURATËoNLy To rHE DEGREE rupluo.si-irie ùÈiHoD'úsÈó.- ",', 5' THE LINES SETW-EEN MATERIAL5 sHowN-oN.THE EXPLORATO]FI EglfNG LOGS REPRE5ENT THEAPPRoxIMÀTE BouNDARlss aETW¡Ei'l'uergnral'îvFÊi-ãñË'iHE rRANsrTroHs uÁi BE .RADUAL.6. GROUNDWATER WAS NOT ENCOUNTERED IN THE EORINGS AT THE TIME OF DRILLING.7. LABORATORY TEST RESULTS¡wc = WATER c.o.llTEl] (,á) (ASTM o zzrø)¡+4 = pERCENTACE nErai¡lÊo oN N0. 1_Srlvç (ASTM 0 a22);-200= PERCENTAGE pASStNc No. zoo srrve lasru ó lljö1. 17 -7 -247 H-PryKUMIAR LECEND AND NOTES Fig. 3 u.!. lo ,o 30 ,ao ão CÓ to lo to to0 c0 i0 70 ü0 t0 a0 l0 t0 lo lti! t at*ll¡r{ tã raH ú0L¡È toutx ardx il¡n tfoo ,to r¡ô lro , ¡ ,tP lr GRAVEL 55 rÉ sANo 56 X UQUID UMIT pLAsTtCtTy ¡NÐEX SAHPIE OFr Silghlly SÍly Sondy Groval t/a- t/1. t I E F ! E I E F ! f; ,oo! ,Ð2 Ìt t¡ytx l.*"¡ I Ll .olo ',or', | ',åål' .,* I .r* t t..oot ,t,,,," '..Jn' | 'J.å ,J '"o1, t I I I lt7t.t loo 2æ CLÂY TO SILT CÛBALES 2'tlt tæ ¡0 to to 60 !o ¡o ü, TO t0 0 ¡taw lllDt CLAY TO 5ILI oR^vEL ¡t9 N s^No 4' UOUID UMN' SAMPLF OF: Sltghtly E¡[y Sondy troval atla ,t0 t¡o ,¡o aß ,ts )6 stLT a¡to ctáY g x FROMrEorfnglO5' stEvE AN^LYSÌS 3/L' t/.. I t0x o tæ t0 :o t0 aô to ô0 70 t0 ¡o .qil ,*, I l.*.1 |.¡ooå .0å '.orl ¡ l.lrtrr, .'o | ¡oo , t.oJ ttt,.r" '..Jo' ' 'J.l ,i ' *1, L l"l ll r¿7t3¡¡ôo coSSLES X 5ILT ÅND CLAY PrÅstrctTY tNoËX FRoIlrÊorlngJâ2.3' 'Itrr.t. l.rt nrulk oÞÞ1, oı1, lo lh.rompltt rhlch w¡n l¡ihd.' n¡. llr-rnl .r.p_rl rholl ñot bÒ npÞdqcrd.r¡capt ln full. rllhoul lhr yrlfi¡n !¡pBvel ol Ksnor â ^nælol.r. lôç,5tryr _snctt¡h tr¡iln! h prrlomid iãøcê_Þ.danc. rlth Agfu û,412. ÂsÎl¡ ct¡6oñrt¿/o? ¡slt¡ Þtta0. HYOROI,FfÊN ANALYSIS stEvË ANAl.Ysts SAND GRAVËL rIHE MEDIUM FINE COARSE }IYORÕMgT€R ^t{aLYsts SAND 6RAVEL FINE HEOIUH lcoansÈ FINÉ COARSE 17-7-247 H-PryKtlMAR GRADATION TTST RESULTS FiE. 4 H-P*KUMARTABLE 1SUMMARY OF LABORATORY TEST RESULTSProject No.17-?-247SOIL TYPÊSlightly Silty Saudy GravelSlightly Silty Sandy GravelUNCONFINEDCOMPBESSIVESTRENGTH{PSF}ATÎERBERG LIñIIITSPt¡sTtcINDEXF/"1LIQUIDLtr'imlo/"1PERCENTPASSINGNO. ?O0SIEVEI10GRADATIONSANOl'/"155364tGRAVELl%'l49NATURALDRYDENS¡TY{pcf}NATURALMOISTURECONTÊNTAORINGOEPTH2.43,85^tt/L/213