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Home My WebLink AboutSubsoil Study for Foundation Design 10.19.21tGrtiiry*fimfffifl*':äü-"' An Employcc Owncd ComPonY 5020 CountY Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 eurail: kaglenwood@kurnarusa,com www.kumarusa,com oflise Locations: Denve¡ (HQ), Parker; colora<lo Springs, Forl collins, Glenrvood Springs, ¿r¡d Summit Cormty, Colorado SUBSOIL STUDY F'OR FOUNDATION DESIGN PROPOSED RESIDENCE LOT D.34, ASPEN GLEN 65 UPLAND GARFIELD COUNTY, COLORADO JOB NO. 2l:7-76t ocToBER 19,2021 PREPARED FOR: NATALLIA KIIARKIIAL 21050 NE 38TH AVENUE, APT 1804 AVENTURA, FLORTDA 33180 nkaspenreale state(â gmail. com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITIONS..... SUBSIDENCE POTENTIAL. FIELD EXPLORATION SUBSURFACE CONDITIONS DESIGN RECOMMENDATIONS ............ FOIjNDATIONS FOUNDATION AND RETAINING WALLS ' FLOOR SLABS UNDERDRAIN SYSTEM SURFACE DRAINAGE LTMiTATIONS.......... FIGURE, I - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - SWELL-CONSOLIDATION TEST RESULTS FIGURE 4 - GRADATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS I 1 1 _) _ ")-L- -3- -6- Kumar & Associates, lnc. @ Project No. 21-7-761 PURPOSE AND SCOPE OF STUDY This report presents the results ofa subsoil study for a proposed residence to be located at Lot D-34, Aspen Glen. 65 Upland, Garfield County, Colorado. The project site is shown on Figwe 1. The putpose of the sfudy was to develop recommendations for the fotrndation design. The study uras conducted in accordance with oul agreement for geotechnical engineering services to Natallia Kharkhal dated September 16, 2t2L Cben-Northern. Inc. previously conducred a preliminary geotechnical engineering study for the subdivision development, report dated December 20, 1991, Job No. 4 ll2 92 and additional geotechnical engineering study for preiiminary plat design. report clated May 28,1993,.Tob No. 4112 92 which have been considered in the current study of Lot D-34. A field exploration program consisting of exploratory borings r'vas conducted to obtain i'formation on the subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to cletermine their classification, ancl other engineefing charaoteristics. The results of the field exploration ancl laboratory testing were anaþzed to develop recolrrnendations for fbundation types, depths and allor,vable pressures f-or the proposed building foundation. This report sumrnarizes the data obtained cluring this study and presents our conclusions, design recommenclations ancl other geotechnical engineering considerations basecl on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION At the time of our study. design plarrs for the residence were in progress. For the purpose of our study, ,we assurne the proposed residence rvill be a one ol two-story wood-frame structure with attached garâge located in the area between the exploratory borings shown on Figure 1. Ground floors could be a combination of structural over crawlspace and slab-on-grade. Grading for the structtue is assgmed to be relatively minor with cut depths between about 2 to 8 t'eet. We assums relatively light foundation loadings, typical of the proposed type of construction, Ifbuildilg loacli¡gs, location or grading plans change significantly Írom those described above, u,e should be notified to re-evaluate the recommendations contained in this report' SITE CONDTTIONS The properly is vacant of structures and vegetated rvith grass and weeds. The ground surface is relatively flat with a gentle slope and around 2 feet of elevation difference across the building area. An active flowing drainage ditch is located along the northwest property line. Kumar & Associates, lnc. @ Project No. 21-7-761 ô- z-- SIJBSIDENCE POTENTIAL Bedr.ock of the Pennsylvanian Age Eagle Valley Evaporite underlies the lower Roaring Fork Valley and the Aspen Glen subdivision. These ¡ocks are â seqlrence of gypsiferous shale, fine- grained sanclstone/siltstone and lirnestone with sorne massive beds of gypsum. There is a possibility that massive -srypsum cleposits associated rvith the Eagle Valley Evaporite underlie portions of the property. Dissolution of the gypsum under certain conditions can car.rse sinkholes to develop and can ploduce areas of localized subsiclence. During previous work in the area, several broad subsidence areas ancl sinkholes were observe<l scattered throughout the Aspen Gleil subdivisio¡ (Che¡-Northem. Inc. lg91). These sinkholes appear similar to others associated with the Eagle valley Evaporite in areas of the Roaring Fofk valley. The site is rrapped as lyingjust outside to the east ofa broad surface depression area and about 700 feet east of a mapped sinkhole. No evidence of subsidence ot sinkholes was obserued on the properly or encountered in the subsurface materials, however, the exploratory boririgs were relatively shallow, fbr foundation design only. Based ûn our present knowledge of the subsurface conditions at the site, it cannot be said for certain that sinkholes will not develop. The risk of firtrue grouncl subsidence at Lot D-34 thloughout the service life of the prroposed structure, in our opinion, is low, h6wever the owner should be aware of the potential for sinkhole development. If fï¡ther investigation of possible cavities in the bedrock below the site is desired, we should be contacted. FTELD EXPLORATION The field exploration for the project was conducted on September 30, 2A21. Two exploratory borings were drilled at the locations shown on Figure 1 to evaluate the subsurface conditions' The borings were advanced with 4-inch diameter continuous flight alrgers powered by a truck- mounted CME-458 drill rig. The borings were logged by a representative of Krunar & Associates. Sarnples of the subsoils were taken with l% inch and 2-inch I.D. spoon sanrplers. The sampiers r¡,ere driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-1586. The penetration resistance vaiues are an inclication of the relative density or consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Figure 2. The samples were retlrned to our laboratory for review by the project engineer and testing Kumar & Associates, lnc. @ Project No. 21-7-761 -3- SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are show'n on Figure 2. The subsoils encountered, below about 1 foot of topsoil, consist of about l'/zfeet of very stiff sandy silty clay or.erlying dense, slightly silty to silty sandy glavel and cobbles with boulders' Drilling in the coarse granular soils with auger equipment rvas diff,tcult due to the cobbles and boulders and practical auger drilling refusal was encountered in the cleposit. Laboratory testing perfonnecl on samples obtained from the borings included natural moisfure content and clensity and gradation analyses. The results of swell-consolidation testing performed on a sample of the clay, presented on Figure 3, inclicates low compressibility under light loading and moderate expansion poterilial when rvetted. Results of graclation analyses performecl on small diameter drive sarnples (minus lt/r-inch fraction) of the coarse grarular subsoils are shown on Figure 4. The laboratory testing is summarizecl in Table 1. No fiee \.vater was encountered in the borings at the time of driiling ancl the subsoils were slightly moist. DESIGN RECOMMENDATIONS FOLINDATIONS Co¡sidering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we recomrnend the building be founded with spreacl footings bearing on the natural granular soils. The clay soils should be sub-excavated where needed down to the nahrral granular soils. The design and constnrction criteria presented below should be observed for a spread footing fourdation system. l) Footings placed on the undisturbed natural granular soils should be designed f'or an allowable bearing pressur€ of 3.000 psf. Based on experience, we expect settlement of footings designed and constructed as discussed in this section will be about 1 inch or less. Z) The footings should have a minirnum width of 16 inches fbr continuous rvalls and 2 îeef for isolatecl Pads' 3) 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 aÍea. Kumar & Associates, lnc. o Project No. 21-7-761 -4- 4) Continuous fogndation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 1Û feet. Foundation walls acting as retaining structures should also be clesignecl to resist lateral earth pressures as discussed in the "Foundation and Retaining 'Walls" section of this lePort. 5) The topsoil, clay soils and any loose disturbecl soils should be removed and the footing beari¡g level extended down to the relatively dense natural granular soils' The exposed soils in footing area should then be moistened and cornpactecl. Voicls created by boulder removal should be backfilled with compacted sand and gravel or rvith concrete. 6) A representative of the geotechnical engineer should obserue all footing excavations prior to concrete placement to evaluate bearing conditions' FOLINDATION AND RETAINING WALLS Fotrndation walls and retaining structures which are laterally supported and can be expected fo 'ndergo only a slight amount of cleflection should be designed f'or a lateral earth pressure c.omputed on the basis of an equivalent fluid unit weight of at least 50 pcf for backfill consisting of the on-site granrilar soils. Cantilevered retaining structures which are separate fi'om the residence and can be expected to deflect sufficiently to mobilize the full active earth pressure condition should be clesigned for a lateral earth pressure cornputecl on the basis of an equivalent fluid unit weight of at leasr 40 pcf for backfill consisting of the on-site granular soils. Backfill sho*ld be a predominantly granular soil and not contain organics or rock larger than 6 inches' All foundation and retaining structures should be designed for appropriate hydrostatic ancl su*harge pressures such as adjacent f'ootings. traffic, construction materials and equipment. Tlie pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the lateral pressure irnposed on a f-oundation wall or retair,ing structure. An underdrain should be provicled to prevent hydrostatic plessul'e buildup behind walls' Backfìll should be placed in uniform litls and cornpacted to at least 9A%o of the maximum standard proctor densíty at a moisture content near optimum. Backfill placed in pavement and walkway areas should be cornpacted to at least 95% of the maximum standard Proctor density' Care should be taken not to overcompact the backfill or use large equipr¡ent near the wall, since this could cause excessive lateral pressure on the u'a11. Some settlement of deep foundation wall backfill shourlcl be expectecl, even if the rnaterial is placed correctly, and could result in distress to facilities constructed on the backtìll. Kumar & Associates, lnc, @ Project No, 21-7-761 -5- The lateral resistance of foundation or rctaining wall footings will be a combination of the sliding resistance of the fboting on the founclation materials and passive eafth pressure against the side of the footing. Resistance to sliding at the bottoms of the tbotings can be calculated based on a coet'ficient of friction of 0.50. Passive pressure of compacted backfìll against the sides of the t'ootings can be calculatecl using an equivalent fluid unit weight of 450 pcf. The coefficient of friction and passive pressure values recouunended above assume ultimate soil strength. Suitable factors of safety shouLd be included in the design to lirnit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads should be a granular material compacted to at least 95% of the maximum standard Proctor density at a moisture content near optimum. FLOOR SLABS The natural on-site soils, exclusive of topsoil ancl clay soils" are suitable to suppoft lightly loaclecl slab-on-grade construction. The clay soils are potentially expansive an<l should be reuroved f}orn beneath slab-on-grade areas and replaced with compacted structural fill as needed. To reduce the effects of some differential movement. flor¡r slabs should be separated from all bearing walls and colunrns with expansion joints which allow unresrrained vertical movernent. Floor slab control joints should be used to reduce damage due to shrinkage crac.king. The requirements f-or joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A rninimum 4-inch layer of free-draining gravel sliould be placed beneath interior slabs to facilitate clrainage. This material should consist of minus 2-incb aggregate rvith at least 50% retained on the No. 4 sieve and less than2o/o passing the No' 200 sieve. All fill rnatedals for support of floor slabs should be compacted to at least 95o/o of maximutn stalldald proctor density at a moishtre content near optimum. Required fill can consist of the onsite granular soils devoid of vegetation, topsoil and oversized rock' UNDERDRAIN SYSTEM Although fiee water was not encountered during our exploration, it has been our experience in the area that local perched groundwater can develop druing times of heavy precipitation or seasonal runoff. Frozen ground during spring tunoffcan create a perched condition. 'We recoinrnend below-grade construction, such as retaining walls, crawlspace and basement areas, be protectecl from wetting and hydrostatic pressure buildup by an uuderdrain system. The drains shoulcl consist of drainpipe placed in the bottom of the wall backfiil surounded above the invert level with free-draining granular rnaterial. The drain shoutd be placed at each level of Kumar & Associates, lnc. o Project No. 2'l-7-761 -6- excavation and at least I foot below lowest adjacent finish grade and sloped at a minimum 7%o fo a suitable gravity outlet, surnp and pump or clrywell. Free-draining granular material used in the underdrain systöm should contain less than 2% passing the No. 200 sieve. less than 50% passing the No. 4 sieve and have a maxirnum size of 2 inches. The drain gravel backfill shotrltl be at least 1 '/zfeet deep. SURFACE DRAINAGE The follor.ving drainage precautions should be observed during construction and maintained at all times after the residence has been completed: 1) Inundation of the foundation excavations and underslab areas should be avoicled during construction' 2) Exterior backfìll should be adjusted to near optimum moistttre and compacted to at least 95Va af the maximum standard Proctor clensity in pavement and slab aleas and to at least 90% of tlie maximunr stanclard Proctor density in landscape areas. 3) The ground surface su'rounding the exterior of the building should be sloped to drain away from the foundation 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 10 fÞet in paved areas. Free-draining wall backfill should be covered vvith filter ftbric and capped lvith about 2 feet of the on-site finer graded soils to reduce suu'face water infiltration' 4) Roof downspouts and drains should clischarge well beyond the limits of all backfill' 5) Landscaping which requires regular heavy iruigation should be located at least 5 feet fi'orn foundation walls. LIMITATIONS This study has been conduc'ted in accordance with generally accepted geotechnical engineering principles and przctices in this arca atthis time. We make no warranty either expless or implied. The conclusions and recommendations submitted in this report are based upon the data obtained fi.om the exploratory borings drilled at the loc¿tions indicaïed on Figure 1, the proposed type of constructio¡ and our experience in the area. Our services do not include determining the presence, pr-evention or possibility of mold or other biological contaminants (MOBC) developing in the futur.e. If the client is concemed about MOBC, then a professional in this special field of practice should be consultecl. Our fîndings include interpolation and extrapolation of the subsurface co¡ditions identified at the exploratory borings and r.ariations in the subsurface Kumar & Associates, lnc. @ Project No, 21-7-761 -7 - conditions may not become evident until excavation is performed. If conditions encountered during construction appear different from those described in this report, we should be notified so that re-evaluation of the recommendations 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 provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to veriff that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommend on-site observation of excavations and founàation bearing strata and testing of structural fiIl by a representative of the geotechnical engineer. Respectfully Submitted, Knmar &,A'ssoeåates, Inc" Steven L. Pawlak, P Reviewed by: \ Daniel E. Hardin, P.E. SLPlkac REFERENCES Chen-Northern, [nc., 1991. Prelíminary Geotechnical Engineeríng Study, Praposed Aspen Glen Development, Garfield County, Colarado. Prepared forAspen Glen Company, dated December 20,lggl,Job No. 411292. Chen-Northern, Inc., !993. Geotechnical Engineering Studyfor Preliminary Plat Design, Aspen Glen Development, Garfield County, Colorado. Prepared for Aspen Glen Company, dated May 28, t993, Job No. 4 lt? 92. 15222o 7t Kumar & Åssociatcs. lne' t Project I'lo. 21"7-761 7.5'Utllìty, Drqlnqge ond Utility Purposes -1 Eosem6nt Droinqge Eoe€mont qs d6pi.tsd ond lobeled on recorded plot /-uzl l;,,i,il: 12.5'Dralnoge Esscm6nt /,Þ ô¡d Ulilíty, oroinogé Utll¡ty Purposoê ÉoEomcnt25.0'Droinoge Eôsêm€nt ---:. (I 7.5'Utllity. DroinEge ond Utllity Purposes Ëobemsnt t ra )7.5'Utlllty, Dro¡¡oge ond Ut¡lity Purpose8 EoEom6nl .t'-.'.: i' ,,: ...'.." { f .- ., ::, ;4,.1,1.:r t...:t '\\ li s;\ t \€920¿?, rJp 20 4A APPROXIMATE SCALE-FEET .rr&_ c,\.,o\ 'q-o Iol Ð34 BORINC 2 o?3,9e9 sq. ft. 0-55 ûcreso BORING I &,\/' t&, -* 21 -7 -7 61 Kumar & Associates LOCATION OF EXPLORATORY BORINGS Fig. 1 ,¡ E {] = ¡ R WC=1.4 +4=50 -2O0=1 5 BORING 1 EL- 6077' BORING 2 EL. 6078' o t5/12 tNC=7.7 ùD=1 12 -200=85 0 s5/6, 4s/6 40/6, 28/6COMBINED 5 50/4 5A/6 10 10 TOPSOIL; ORGANIc SANDY SILT AND CLAY' MOISI' RED-BROWN CLAY (CL); SILTY, SANDY, VERY STIFF, SLIGHTLY MOIST' RED. GRAVEL AND COBBLES (GM-GP); SLIGHTLY SILTY T0 SILTY, SANDY, BOULDERS, DENSE, SLIGHTLY MOIST, GRAY-BROWN. DRIVE SAMPLE, 2_INCH I.D. CALIFORNIA LINER SAMPLE. i DRTVE SAMPLE, 1 3/8-INCH l.D. SPLIT SPoON STANDARD PENETRÂT|oN TEST AE,'^ DRIVE SAMPLE BLOW COUNT' INDICATES THÁT 15 BLOWS OF A 14o-POUND HAMMER '"/ '' FALLTNG JO TNCHES WERE REQUIRED IO ÐRIVE THE SAMPLER 12 INCHES. PRACTICAL AUGER REFUSAL. NOTES 1 . THE EXPLORATORY BORINGS WERE DRILLED ON SEPTEMBER 50, 2A21 WffH A 4-II'{CH 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 ELEVATIONS OF THE EXPLORATORY BORINGS WERE OBTAINEÐ BY INTERPOLATION BETWEEN CONTOURS CIN THE SITE PLAN PROVIDEÐ' 4. THE EXPLORATORY BORING LOCATIONS AND ELEVATIONS 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 APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING. 7. LABORATORY TEST RESULÏS: WC = WATER CONTENT (%) (ASTM D2216); DD = DRY DENSITY (pcf) (ASTM Ð2216); +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (¡STM POSIS); -2oo= PERCENTAGE PASSING NO. 200 SIEVE (ASTM 01140). 5 FIJbltL I :E t-- TL LJÕ t-LJ L¡l t! I-t-tL L¡JÕ I Fig. 2LOGS OF EXPLORATORY BORÍNGS21-7 -761 Kumar & Associates Ê SAMPLE OF: Silìy SondY CloY FROM: Boring 2 @ 1' tNC = 7.7 "/6, DD = 112 pcî -2AO = 85 % EXPANSION UNDER CONSTANT PRESSURE UPON WETTING nôt rith D-S46. 5 a "tS JJ LJ =an I zotr U =otnza(J o -1 -2 5 _ KSF 10 Fig.3SWELL-CONSOLIDATION TTST RESULTSKumar & Associates21 -7 -761 e € I ı w fo0 90 ao 70 50 40 30 20 lo o HYDROMETER ANALYSIS SIEVE ANALYSIS IIME REÆIÑOS 24 ffRS 7 HRs ¿utN r utN I' g.S. S'ANDARD SERIF ¡5ô ¿¡O ¡3ô ¡16 ¡10 ¡E CgR SQUARE OPËNINôS a/^. a/.' t 1/t' I t ì. I I I ì ¡ ¡t i I i ¡ I I i i I I I I j I I I I i ¡ I ti o 10 20 30 Æ c0 60 70 a0 90 foo 4 D .125 2.O ÕF PARTICLES IN MILLIMETERS CLAY TO SILT COâBLES GRAVEL 50 % SAND 35 % LIQUID LIMIT - PLASTICITY INDEX SÁMPLE OF: Silly Sondy Grovel SILT AND CLAY 15 % FRoM: Boring 1 O 2.5' & 5' (Combined) Those l€sl r6sulls opply only lo lhe sqmÞl€s which war! ld!l?d, The l.sllng report sholl nql b. rcproducrd, €xc€pt ln full, wlthoul lhe wrlllen dpprovol of Kumor & Asroçlqles, lnc. S¡sv€ onofysì! lerllng ¡e perfomsd ìn qccordqnce wllh ASÎM D6913. ASTM D7s28, ASTM C156 ond,/or ASÍM Dlt40. GRAVELSAND FIN E COARSEFf NÊ MEDTUM ICOARSE 21 -7 -7 61 Kumar & Associates GRADATION TIST RESULTS Fis. 4 KtfXurar & Associatesn lnc,'Geotechnical and Materials Engineersand Environmental ScientistsTABLE 1SUMMARY OF LABORATORY TEST RESULTSNo.21-7-761Silfy Sandy ClaySOIL TYPESilty Sandy GravelUNCONFINEDCOMPRESSIVESTRENGTHATTERBERG LMFSUQUID LIMITPLASTICINDEX85153550PERCENTPASSING NO,200 stEvETL2(%)SAND(%)GRAVELNATURALDRYDENStrY77{%lNATURAL¡¡IOISTURECONTENTr.4IZt/z and 5combinedItft)DEPTH2SAMPLE LOCATIONBORING