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Home My WebLink AboutSubsoil StudyI (+Â åffiil[#:l'fÉ:fr,:nËd **.5020 County Road 154 Glenwooel Springs, CO 81601 phone: (970) 915-7988 fa"x: (970) 945-8454 email : kaglenwood@kulnarusa.com An Ëmployec ùrned Compony ww*.kumarusa.com Office l-ocations:Denver (HQ), Parke¡ Colorado Springs, Fort Collins, Clenwoocl Springs, and Summit County, Colorado SUBSOIL STUDY FOR FOTINDATION DESIGN PROPOSED RESIDENCE TRACT 4, ANTLERS ORCr{ARI) SOUTHEAST CORNER OF SILT MESA ROAD AND ANTLERS LANE GARFIELD COUNTY, COLORADO PROJECT NO.21-7-191 APRrL 8,2021 PREPARED FOR: OSCAR MARTINEZ P.O. BOX 4s9 srLT, coLoRADO 81652 l. o. a m a rtin ez(ù.hotmai l. com TABLE OF CONTENTS PURPOSIJ AND SCOPE OF STUDY ....... PROPOSED CONSTRI.ICTION SITE CONDITIONS.... FIELD EXPLORATION 1 ...... - 1 - SUBSURFACE CONDITIONS FOUNDATION BEARING CONDITIONS DESIGN RECOMMENDATIONS FOI.'NDATIONS TOUNOEUON AND RETAINING WALLS. FLOOR SLABS LTNDERDRAIN SYSTEM J" J- J- 4- 5- 6- SURFACE DRAINAGE LIMITATIONS FIGURE 1 . LOCATION OF EXPLORATORY BORINGS FIGT]RE 2 - LOGS OF EXPLORATORY BORTNGS FIGURE 3 . LEGEND AND NOTES FIGURES4AND5-SWELL-CONSOLIDATIONTESTRESULTS TABLE 1- SLMMARY OF LABORATORY TEST RESULTS ...- 6 - Kumar & Asgociates, lnc. @ Project No.21'7'191 PURPOSE AND SCOPE OF STUDY This report presents the results ofa subsoil study for a proposed residence to be located onTract 4' Antlers orchard, southeast corner of silt Mesa Road and Antlers Lane,Garfield county,colorado' The project site is shown on Figure l. The purpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with ourproposal for geotechnical engineering services to oscar Martinezdated Febru ary 5,2021. A field exploration program consisting of exploratory borings was conducted to obtain information on the subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their crassification, compressibilify orswell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzedto develop recommendations for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained duringthis study and presents our conclusions, design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The proposed residence will be a one-story wood frame structure over a crawlspace or slab-on-grade' Grading for the structure is assumed to be relatively minor with cut depths between about2 to 5 feet' we assume relatively light foundation loadings, typical of the proposed fype of construction. If building loadings, location or grading plans change significantly from those described above,we should be notified to re-evaluate the recommendations contained in this report. SITE CONDITIONS The site is a vacant, relatively flat,hay field. The lot slopes down to the southwest at about 2 percent grade' There was 4 to 6 inches of snow covering the site at the time of our site visit. FIELD EXPLORATION The field exploration for the project was conducted on borings were drilled at the locations shown on Figure 1 February 16,2021. Two exploratory to evaluate the subsurface conditions Kumar & Associates, lnc. o Project No. 21.7-191 a-L- Tlrcboringswerea<]vatrcedwith4inchdiametercontinuousflightaugerspcrweredbyatruck- mounted cME-458 dri[ rig. The borings wefe loggcd by a representative of Kumar & Associates, lnc. Samples of the subsoïls were taketr with 1% inch and 2 inch I'D' spoon samplers' The samplers weredrivenintothesubsoilsatvariousdepthswitlrblowsfromal40poundhammerfalling30 inches. This test is similar to the standard penetration test described by AsrM Method D-1586' The penetration resistance varues are an indication of the relative density or consistency of the subsoils. Depths at which the samples were takcn and the penetration resistance values are shownontheLogsofExploratoryBorings,Figure2'Thesampleswereretumedtoour laboratory for review by the project engineer and testing' SI]BSURFACE CONDITIONS GraphiclogsofthesubsurfaceconditionsencounteredatthesiteareshownonFigure2.The subsoilsconsistofabout/zfootoftopsoiloverlyingir9%feetofmediumstiff,sandysiltyclay. Below20feetdeep,thesoilsconsistedtlfrrrediumstifftostiffclayanclsiltinBoringland relatively dense, silty sand and gravel in Boring 2' Laboratorytestingperformedonsamplesobtainedfromtheboringsincludednaturalmoisture content and density and finer than sand size gradation anaryses. Results of swe'-consolidation testing performed on relatively undisturbed drive samples, presented on Figures 4 and 5' indicate moderatecompressibilityunderconditionsofloadingandwetting'Thelaboratorytestingis summarized in Table 1' Free water was encountered in the borings at the time of drilling at depths of 6% feet in Boring 1 andllfeetinBoring2.Thesubsoilsweremoisttowetwithdepth. FOUNDATION BEARING CONDITIONS The clay subsoils at this site have reratively row strength and will tend to oompress u;hcn loaded' Lowbearingpressurespreadfootingfoundationscanbeusedatthissite,providedthatsome settlement on the order of 1 to 2 inches is tolcrable' Kumar & Associates, lnc. @ Project No, 21-7'191 -J- DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural clay soils with a risk of settlement. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed onthe undisturbed natural clay soils should be designed for an allowabre bearing pressure of 1,000 psf, Based on experience, we expect sefflement of footings designed and constructed as discussed in this section will be about I to 2 inches. 2) The footings should have a minimum width of 20 inches for continuous walls and 3 feet for isolated 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 area, 4) Continuous foundation walls should be heavily reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 14 feet. Foundation walls acting as retaining structures should also be designed to resist lateral earth pressures as discussed in the "Foundation and Retaining Walls,, section of this report. 5) All existing topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the natural subsoils. The exposed soils in footing area should be compacted. 6) A representative ofthe geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FOT'NDATION AND RETAINING V/ALLS Foundation walls and retaining structures which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for alaterul earth pressure computed on the basis of an equivalent fluid unit weight of at least 55 pcf for backfill consisting Kumar & Associates, lnc. o Project No. 21.7.191 4 uf the on-site finc-grained soils. Cantilevered retaining structures which are separate from the residence and can be expected to cleflect sufficicntly to mobilize thc flill active earth pressure condition shoultl be designed for a lateral earth pressure compntecl on thc basis of an equivalent fluid unit weight of at least 45 pcf for backfill consisting of the on-site fine-grained soils' All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, traffic, construction materials and equipment' The 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 imposed on a foundation wall or retaining structure' An underdrain should be provided to prevent hydrostatic pressure buildup behind walls' Backfill should be placed in uniform lifts and compacted to at least 90% of the maximum standard Proctor density at a moisture content near optimum' Backflrll in pavement and walkway areas should be compacted to at least 95% of the maximum standard Proctor density' care should be taken not to overcompact the backfill or use large equipment near the wall' since this could cause excessive lateral pressufe on the wall. some settlement of deep foundation wall backfîll should be expected, even if the material is placed correctly, and could result in distress to facilities constructed on the backfill. Backfill should not contain organics, debris or rock larger than about 6 inches. The lateral resistance of foundation or retaining wall footings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth pressure against the side of the footing. Resistance to sliding at the bottoms of the footings can be calculated based on a coefficient of friction of 0.30. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 300 pcf' The coefficient of friction and passive pfessure values recommended above assume ultimate soil strength. suitable factors of safety should be included in the design to limit 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 compacteil to at least 95% of the maximum standard Proctor density at a moisture content near optimum' FLOOR SI,ABS The natural on-site soils, exclusive of topsoil, are suitablc to support lightly loaded slab-on-grade construction. To reduce the effects of some differential movement' floor slabs should be Kumar & Associates, lnc. @ Proiect No.21.7'191 5 separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab control joints should be used to reduce damage due to shrinkage cracking' The requirements forjoint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A minimum 4 inch layer of road base gravel should be placed beneath slabs to provide support. This material should consist of minus 2-inch aggregate with at least 50Yo retained on the No. 4 sieve and less than l2o/o passingthe No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95%o of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of imported granular soils devoid of vegetation, topsoil and oversized rock or road base. We recommend vapor retarders conform to at least the minimum requirements of ASTM p1745 Class C material. Certain floor types are more sensitive to water vapor transmission than others. For floor slabs bearing on angular gravel or where flooring system sensitive to water vapor transmission are utilized, we recommend a vapor barrier be utilized conforming to the minimum requirements of ASTM 81745 Class A material. The vapor retarder should be installed in accordance with the manufacturers' recommendations and ASTM 81643. LINDERDRAIN SYSTEM An underdrain should not be needed provided the proposed, crawlspace is not more than 3 feet below exterior grade. We recommend below-grade constructiono such as retaining walls, deep crawlspace and basement areas (if any), be protected from wetting and hydrostatic pressure buildup by anunderdrain system. If installed, the drains should consist of drainpipe placed in the bottom ofthe wall backfill surrounded above the invert level with free-draining granular material. The drain should be placed at each level ofexcavation and at least I foot below lowest adjacent finish grade and sloped at a minimum 1%oto a suitable gravity outlet or sump and pump. Free-draining granular material used in the underdrain system should contain less than 2o/o passingthe No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least l%feet deep. Kumar & Associates, lnc. @ Project No.21.7-191 -6- SURFACE DRAINAGE Thc following drainage precautions should be observed during construction and nraint¿irled at all times after the residence has been completed: 1) Inundation ofthe foundation excavations and undcrslab areas should be avoided during construction. 2) Exterior backtìll should be adjusted to near optimum moisture and cornpacted to at least 95% of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximurn standard Proctor dcnsity in landscape areâs. 3) The ground surface sunounding 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 10 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in paved areas. Free-draining wall backfill (if any) shoutd be covered with filter fabric and capped with about 2 fee't" of the on-site soils to reduce surface water infiltration' 4) Roof clownspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from foundation walls. Consideration should be given to use of xeriscape to reduce the potential for wetting of soils below the building caused by inigation. LIII¡TITATIONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area atthis time. We make no warranty either express or implied. The conclusions and recommendations submitted in this report are based upon the data obtained from the exploratory borings drilled at the locations indicated 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 (lvIOBC) developing in the future. If the client is concerned about MOBC, then a professional in this special field of practice should be consulted. Our findings include interpolation and extrapolation of the subsurface conditions iclentified at the exploratory borings and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered Kumar & Assoclates, lnc. @ Project No, 21-7-191 -7 - 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 verifr that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. vy'e recommend on-site observation of excavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfrrlly Submitted, Kumar & Daniel E. Hardin, Reviewed by:#,/- Steven L. Pawlak, p.E. DEHlkac cc: Beatriz Soto .bcdu¿@hiåhcquqlqybd,_c_ffi Kumar & ÁssoGíates, l¡ç. :r, Projeet No. tf-I-i9,t 030 APPROXIMATE SCALE_FEET Fig. 1LOCATION OF EXPLORATORY BORINGSKumar & Associates21 *7 -191 ¡ É ! BORING 't 5 BORING 2 EL. 5529',EL.5527 0 7/12 7/12 0 8/12 WC=24.9 DD=96 5 4/12 WC=24.6 DD=99 5 _>_s/12 WC=25.8 DD= 1 00 -200=85 4/ 12 tNC=24.7 DD=95 2/t2 10 4/12 l0 f-¡¡l l&ll¿ Itt--a- L¡Jo l5 f5 t--l¡¡ l¡JL I-F-fLt¡lÕ 7 /12 4/12 20 204/12 38/12 WC=10.7 DD= 1 25 -200=1 5 25 13/12 Y,lC=22.3 DD=101 -200=62 38/12 25 30 30 21 -7 -191 Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 2 LEGEND- ToPSOIL: RooT zoNE, oRGANlc SILTY SANDY CLAY, MEDIUM STIFF, MolST, DARK BRowN. CLAY (CL): SILTY, SANDY, MEDIUM STIFF, MOIST TO WET', BROWN CLAYANDSILT(CL-ML):VERYSANDY'MEDIUMSTIFF'TOSTIFF'WET'BROWN' SAND AND GRAVEL (GM-SM): SILTY, DENSE' WET' BROWN F ¡ DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE' DRIVESAMPIE,lS/}-INCHI.D.SPLITSPooNSTANDARDPENETRATIoNTEST. ? / 1 2 PXIïEI N 3 S \î,.î"1.,,Ê'#- l, åü', å?â' iå THJ "' åloYi* 3I' å "i Î ¡3 ff H$.' & OEPTH TO WAÏER LEVEL ENCOUNTERED AT THE TTME OF DRILLING' -+ DEPTH AT WHICH BORING CAVED FOLLOWING DRILLING. IIAMMER NOTES 1. ÏHE EXPLoRAToRY BoRlNGs WERE DRILLED oN FEBRUARY 16,2021 wlTH A 4_lNcH DIAMETER coÑrtuuous-FLIGHT PowER AUGER' 2. THE LOCATIONS OF THE EXPLORAT-O|Y BORINGS WERE MEASURED APPROXIMATELY BY PACING Énov-rÈrrunrs lHowÑ oN THE slrE PLAN PRovIDED' 3. THE ELEVATIONS OF THE EXPLORÂT.ORY BORINGS WERE OBTAINED BY INTERPOLATION BETWEEN cóñrouns oN THE slrE PLAN PRovIDED' 4.THEEXPLoRAToRYBoRINGLocATIoNSANDELEVATIoNSSHoULDBEcoNSIDEREDACCURATE oNLy ro rHE lÈonEÈ IMPLIED BY THE METHoD usED' s.THELINESBETWEENMATERIALS,lJgwNoNTHEEXPLoRAToRYBoRINGLoGSREPRESENTTHE AppRoxrMAïE B.'NDARTES BETwEEN"i,iÀrËär¡l'îvpÊs-Áño ïHE rn¡uslrloNs MAY BE GRADUAL' 6.GRoUNDWATERLEVELSSHowNo!-IHELoGsWEREIIEASUREDATTHETIMEANDUNDER coNDITtoNs INDIcATEÐ. ruucru¡rlo¡¡i-lri-iñe wnrEn LEVEL MAY occuR wlTH TIME' 7. LABORATORY TEST RESULTS: Wc = WATER CONTENT (%) (ASTM D2216); DD = DRY DENSITY (PCI) (NSTU OZZIø)| -200= penceÑrÀcE pissinè No' 2oo sirvr llsru ott¿o); Flg. 3LEGEND AND NOTESKumar & Associates21 -7 -191 Ë I I SAMPLE OF: Sondy Si$y Ctoy FROM:Boring2OS' WC = 24.6 %, DD = 99 pcf 2 às 0 JJl¡¡ =tn -z I z.9_,l-r ô =o2-aoo -8 -10 - KSF t0 100 2 òs 0 JJ l¡J =an -¿ I z. S-+ ô =op-ø o() -8 SAMPLE OF: Sondy Sitty Ctoy FROM:Boringl@,l0' WC = 24,7 %, Dù = 96 pcf *.lt h# rþt bc 'ttlut NO MOVEMENT UPON WETTING -10 21-7-191 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 4 SAMFLE OF: SondY SiltY CloY FROM:BoringÍe2.5' \{C = 24.9 t6, DD = 96 Pcf EXPANSION UNDER PRESSURE UPON CONSTANT WETTING .. .' .'-- i - of ln 2 0 n-2 j-1 l¿l =Ø r_6 zotrôı =-o(f anz.oo -10 100t0t.0 Fig. 5SWELL-CONSOLIDATION TEST RESULTSKumar & Associates21 -7 *191 ¡ Ê l (+rt,rj,çlfi*-ffffif üri ,"; *",TABLE 1SUMMARY OF LABORATORY TEST RESULTSSOIL TYPESandy Silty ClaySandy Silty ClaySandy Silty CtayVery Sandy SilryClaySandy Silty ClaySilty SandUNCONFINEDCOMPRESSIVESTRET.¡GTH(psf)ATTETPLASTICINDEXl/"1LIQUID LIMÍÍ{%lPERCENTPASSING NO.200 stEVE856215NATURALDRYDENS.lrYGRAVELSANDP/"1$t96100951019912sNATURALMOISTURECONTENT(olol24.923.824.722.324.610.7DEPTH(ft)ZYt7%1025520BORING2No.2l'7.191