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Home My WebLink AboutSubsoils Study for Foundation DesigntC iffifi'å-#l:Ëin[ir;o*"' Ân Employcc Onrncd Conpory 5020 Cou¡ty Road l-54 Glenwood Springs, CO 816t1 phone: (970) 945-7988 far (970) 945-8'15'1 email kaglenrvoodfòlumarusacom www.kumarusa.com Olfice Locations: Denver (HQ), Parker; Colorado Springs, Fort C¡¡nlins, Gltr$*þotl SpringE ¿n¡l Sunmút Glrnþ, Colorado ffiii,'f,ii'ii¡iffiÐ SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE 3l ROYAL COACH}VIAN LOT 28, ROARING FORK MESA AT ASPEN GLEN GARFIELD COUNTY, COLORADO PROJECT NO.2l-7-202 APRrL 20,202t PREPARED FOR: RONDA CAMPBELL P.O.BOX 4272 FRISCO, COLORADO 80443 rondacampb ell@comcast.net TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY... PROPOSED CONSTRUCTION SITE CONDITIONS SUBSIDENCE POTENTIAL FIELD EXPLORATION SUBSURFACE CONDITIONS DESIGN RECOMMENDATIONS FOUNDATIONS FOUNDATION AND RETAINING WALLS. FLOOR SLABS UNDE,RDRAIN SYSTEM SURFACE DRAINAGE LIMITATIONS FIGURE, I - LOCATION OF EXPLORATORY BORINGS FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURE 4 - SWELL-CONSOLIDATION TEST RESULTS FTGURE 5 - GRADATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS 1 -l - 1 1 -L- ,,-2 - .-6- Kumar & Associates, Inc. @ Project flo.21-7-21lll PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil stucly for a proposed residence to be located on Lot 28, Roaring Fork Mesa, Aspen Glen Subdivision, 31 Royal Coachman, Garfield County, Colorado. The project site is shown on Figure 1. The purpose of the study r,vas to develop recommendafions for the founclation design. The study was conducted in accordance with our agfeement fbr geotechnical engineering serr,'ices to Ronda Campbell dated Febmuy 12,2027. A iield exploration program consisting of exploratory borings was conducted to obtain information on the subsurface conditions. Samples of the subsoiis obtained during the field exploration were tested in the laboratory to determine their classification, compressibility or swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations for tbundation types, depths and allowable pressures for the proposed building foundation. This leport sumn arizes the data obtained during this stucly ancl presents our conclusions. design reconunenclations and other geotechnical engineering considerations based on the proposed construction and the subsurface conclitions eucounterecl. PROPOSED CONSTRUCTION The proposed residence will be a one-story wood-frame structure with partial second story and attached three-car garage. Ground floors will be structural over crawlspace for the living areas and slab-on-glade for the garage. Grading for the structure is assumed to be relatively minor witlr cut depths between about 2to 4fbet. V/e assume relatively light foundation loadings, typical of the proposed type of constn¡ction. lf building loadings, location or grading plans change significantly from those described above, we shoqld be notified to re-evaluate the recommendations contained in this report. SITE CONDITIONS The subject site was vàcarú at the tirne of our fleld exploration. The ground surface is gently sloping down to the east at a grade of around 5 percent. A dry drainage swale borders the lot to the north. Vegetation consists of grass with bmsh in the drainage swale north of the lot. STIBSIDENCE POTENTIAL Bcdrock of thc Pennsylvanian age Fagle Valley Eva¡xtrite unclerlies the site. Tltese roclcs are a sequence of gypsiferous shale, fine-grained sandstone ancl siltstone with sorne rnassive beds of Kumar & As¡ociates, lnc. ó Preþct t{o" 21-?¿02 a gypsum ancl limestone. There is a possibility that massive gypsum deposits associated with the Eagle Valley Evaporite underlie portions of the lot. Dissolution of the gypsum under certain conditions can cause sinkholes to develop and can produce areas oflocalized subsidence. Duling previous work in the area, several sinlcholes were observed scattered throughout the Aspen Glen Development, mainly east of lhe Roaring F-ork River. These sinkholes appear similar to others associated with the Eagle Valley Evaporite in areas of the lower Roaring Fork River Valley. Sinl<holes were not observed in the immediate area of the subject lot. No evidence of cavities was encountered in the subsurface materials, howevero the exploratory borings were relatively shallow. for fotrndation design only. Based on our present knowledge of the subsurface conditions at the site, it canÍot be said for certain that sinkholes will not develop. The risk of futule ground snbsidence on Lot 28 thloughout the seruice life of the proposed residence, in our opinion, is low; however, the owner should be made aware of the potential for sinkhole development. 1f further investigation of possible cavities in the bedrnck below the site is desired, we should be contacted. FIELD EXPLORATION The {ield exploration for the project was conducted on March 23,202l. Two exploratory borings were drilled at the locations shown on Figure I to evaluate the subsurface conditions, The borings were advanced with 4 inch diarneter continuous flight augers powerecl by a truck- mounred CME-458 drill lig. The borings were logged by a representative of Knmar & Associates, Inc. Samples of the subsr¡ils were taken with 1% inch and 2 inch I.D. spoon samplers. The sanplers were driven into the subsoils at various depths with blows from a 140 pound harnmer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-l586. The penetration resistance values are afl indication of the relative density or consistency of the subsoils. Depths at which the sarnples were taken and the penetration resistance values are shown on the Logs of Exploratory Borings, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS Graphic logs of the subsurface conditions encountered at the site are shown on Figure 2. The subsoils consist of about I foot of topsoil overlying2lYz to 241/z feet of rneclium dense to clense, Kumar & Associates, lnc. @ koject f{o.21-7-202 -3- silty sand with gravel layers. Relatively dense, silty sand and gravel was encountered at depths of 22% to 25% feet and extended down to the drilled depth of 30 fbet. Laboratory testing perfbrmed on samples ol¡tained fiom the borings included natural moisfure contont and gradation analyses. Results of swell-consr¡lidation testing perfbrmed on relatively un<listurlred drive samples, presented on Figure 4, tndicate low to moclerate compressibility under existing moisture conditions and light loading and a nil to low expansion poterrtial when wetted under constant light surcharge. Our experience in the area indicates the swell potential is an anomaly and can be discounted in foundation design particularly due to the depth of the sample tlrat srvelled at 20 feet. Results of gradation analyses performed on small diarneter drive samples (minus l%-inch fractiori) of the coarse grannlar subs¡rils are shown on Figure 5. The laboratory testing is summarized in Table 1, No free water was encoulltered in the borings at the time of drilling and the subsoils were slightly moist to moist. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the explomtory borings and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural granular soils with a risk of settlement. The settlement potential is mainly from wetting and precautions should be taken to keep the bearing soils dry. The design and constnrction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed natural granular soils should be designecl for an allowable bearing pressure of 2.000 psf. Based on experience, we expect settlement of footings designed and constnrcted as discussed in this section will be about I inch or less. 2) The f-ootings should have aminimurn width of l8 inches for continuous wa1ls ancl 2 feet for isolated pads. 3) Exterior footings and footings beneath nnheated areas should be provided with adequate soil cover above their bearing elevatiorr for frost protection. Placement of foundations at least 36 inches below exterior grade is typically used in this atea. Kumar & Associates, lnc.@ Project l{o.21-7-202 -4- 4)Continuous foundation walls shoulcl be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 12 feet. Foundation walls acting as retaining structures should also be clesigned to resist lateral earth pressures as disc¿rssed in the "Foundation and Retaining Walls" section of this report. All existing fiIl, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended clown to the relatively clense natural granular soils. The exposed soils in footing area should then be moistened and compacted. A representative of the geotechnical engineer should observe all footing excavations prior to conclete placement to evaluate bearing conditions. FOLINDATION AND RETAINING WALLS 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 a lateral earth pressu'e computed on the basis of an equivalent fluid unit weight of at least 50 pcf for backfill consisting of the on-site soils. Cantilevered retaining strucfures rvhich are separate from the residence and can be expected to deflect sufficiently to mobilize the ftilt active earth pressure contlition should be designecl for a lateral earth pressure computed on the basis of an equivalent fluicl unit weight of at least 40 pcf for backfiil consisting of the on-site soils. All foundation ancl retaining structures should be designed for applopriate hydrostatic and surcharge ptessures such as adjacent tbotings, traffic, constl'uction materials and equiprnent. The pressures recommended above assume drained conditions behind the walls and a horizontal backfîll surface. The buildup of water behind a wall or an upward sloping backfill surface will increase the laferal pressure imposed ou a foundation wall or retainiug structure. An underdrain should be provided to prevent hydrostatic pressü'e buildup behind walls. Bacl<fill shoulcl be placed in urrifomr lifts ancl compactecl to at least 90% of the llaxlmuln standard Proctor clensity at a moisture content near optimum. Backfill placed in pavement and r,valkway areas shr¡uld be compacted tr¡ at least 95% of rhe maximum standard Proctor density. Care should be taken not to overcompact the baskfill or use large equiptne¡rt near the wall, since this could cause excessive lateral pressure on the wall. Sorne settlement of deep foundation wall backfîll should be expected, even if the material is placed corectly, and could result in distress to facilities constructed on the backfill. Backfill shoLrld not contain organics, debris or rock larger than about 6 inches. 5) 6) Kumar & Assæiates, lnc. @ Prcjeû,No.21-7-2t2 -5- The lateral resistance of foundation or retaining lvall footings will be a combinatiorr 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 bottorns of the footings can be calculated based on a coef-fîcient of friction of 0.40. Passive pressure of compacted backfill agaínst the sides of the footings cal be calculated using an equivalent fluid unit weight of 375 pcf. The coeffìcient of friction and passive pressure values recommended above assunre ultimale soil strength. Suitable factors of safety shoulcl be included in the design to limit the strain which will occur at the ultimate strength, pafticularly in the case of passive resistance. Fill placed against tlre sides of the footings to resist lateral loads should be compacted to at least 95o/o of the maximum standard Proctor density at a moisture content near optimum. FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade conshuction. To reduce the effects of some differential tnovement, floor slabs shoulcl be separated fi'om all bearing walls and columns with expansion joints which allow unrestrained vefiical rnovement. Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirenrents f'or joint spacing and slab reinf-orcement should be established by the designer basecl on experience and the intended slab use. A minimum 4 inch layer of fiee- draining gravel should be placed beneath basement leve1 slabs to facilitate drainage. This material should consist of minus 2 inch aggregate with at least 50% retained on the No. 4 sieve and less than2o/o passing the No. 200 sieve. All fîll materials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a rnoisture content near optimum. Required fill can consist of the on- site granular soils devoicl of vegetation, topsoil and oversizecl rock. We recommend vapor retarders confonn to at least the minitnum requirernents of ASTME1745 Class C material. Certain floor types are more sensitive to water vapor transrnissìon than others. For floor slabs bearing on angular gravel or r.vhere flooling system sensitive to water vapor transmission are rfilized, lve recommend a vapor barier be utilized conforming to the tnininum requirernents of ASTM 81745 Class A material. The vapor retarcler shoulcl be installect in aooordance r.vith the rnanufacturers' recoÍtmendations and ASTM 81643. UNDERDRAIN SYSTEM Although free water was not encountered during our exploration, it has been our experience in the area that local perched grounclwater can develop during times of heaq' precipitation or seasonal runoff. Frozen grouncl cluring spring runoff can create a perched condition. We lftmr t Associates, lltc. o Froþ* 1lo. 21-7-202 -6- recommend below-grade construction, such as retaining walls and crawlspace areas, be protected fiom wetting and hydrostatic pressure buildup by an unclerdrain system. The drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with tree-draining granular material. The drain should be placed at each level of excavation and at least I foot below lowest adjacent finish grade and sloped at a minimum 1a/o to a suitable gravity outlet or drywell. Free-draining granular material used in the underdrain systenr should contain less than 2o/o passing the 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 1% feet deep. SURFACE DRAINAGE The fbllowing drainage precautions sliould be obsen'ed cluring construction and maintained at all tirres after the residence has been cornpleted: 1) Inunclation of the fbundation excavations and underslab areas should be avoided during construction. 2) Exterior backfill should be adjusted to near optìmun moisture and compacted to at least 95o/o of the maxirnum standard Proctor density in pavement and slab areas and to at least 90o/a of the marimurn standard Proctor density in landscape areas. 3) The grouncl surface sumounding the exterior of the building should be sloped to clrain away from the foundation in all clirections. We recommend a tninimun slope of 6 irches in the first 10 feet in unpavecl areas and a miuimum slope of 2% inches in the first 10 feet in paved areas. Free-draining wall backfill should be covered with filter fabric and capped with about 2 feet of the on-site finer gracled soils to reduce surfbce water infiltration. 4) Roof downspouts and drains should discharge well beyond the limits of all backftll. 5) Landscaping which requires regular heavy irrigation should be locatecl at least 5 fèet fiom foundation walls. Corsicleration should be given to use of xeriscape to reduce the potential for wetting of soils below the building caused by irrigation. LIMITATIOT{S This study has been conclucted in accordance rvith generally accepted geotechnical engineering principles and practices in this area at this time. We make no waranty either oxpress or irnplied. The conclusions and recommenclations submitted in this report are based upon the data obtained Xumar&lssoriab, lnc. @ Project No. 21-7-202 -7 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 (MOBC) developing in the future. If the client is concemed about MOBC, then a professional in this special field of practice should be consulted. Our findings include interpolation and extrapolation of the subsurface conditions identified at the exploratory borings and variations in the subsurface conditions may not become evident until excavation is performed. If conditions encountered during construction appe& 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 verifu 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 ofexcavations and foundation bearing strata and testing ofstructural flll by a representative of the geotechnical engineer. Respectfully Submitted, Kumar & James H. Parsons, Reviewed by: Daniel E. Hardin, P.E. JHP/kac tt H: 58663 Kumar & Associates, lnc. ¡Project No. 21"7.202 4 #\u -r'- X,o,)* ov & utiltiYut Eoætùa\ È ta{'* *- -ttt'ûj 0í;{ N,f,TYAPETT;W'#û TOP ff CAP ELEV. 6078,1 e,Å,{t}\tr'f8 ûüJ{1&t 7-5' Util¡ty D.aÍ.togo,. .þ Utlllty Putpoe€e \ Edffiên{ t.-e ta0' ( \t. *-- BONING Io 7.5'Utlllly Orolnoga & Ut¡llty Purposee Edsamênt Vot 2B \ o.26s Ac. l¿. BORING 2\.o q¡ (s \""1 \ :.'it-, \:?.'\ -O¿**\ \t \ --5t.9 \ & I {,r.5' uillt/ & Pcdest lq Edæmet I a I 'I 0 APPROXIMATE SCALE-FEEf 1 Fig. 1LOCATION OF EXPLORATORY BORINGST -7 -242 Kumar & Associates WC=1.5 +4=44 -2QO=1 4 BORING 1 EL. 6081.5' BORING 2 EL. 6079.5' 0 0 so/2 24/12 5 63/12 21 /12 WC=1.0 DD=121 -200=1 3 5 54/12 14/12 10 10 21/12 WC=3.4 -2Ð0=29 11 /12 t-t¡J UJtL I-l-"-IL t¡Jô 15 15 FLIl¡lL ITl-"fL UJô t4/12 s/ 12 20 20 14/12 WC=8.1 DD= 1 02 -2OO=57 32/12 WC=7.0 DD='l 1 3 -200=88 25 5a/3 25 30 50/2 50 WC=2.0 +4=13 -ZQO=29 21-7 -202 Kumar & Associates LOGS OF TXPLORATORY BORINGS Fig. 2 LEGEND TOPSOIL: SAND, SILTY, CLAYEY, SCATTERED GRAVEL, ORGANICS, FIRM, MOISI, RED BROWN. SAND (SM)I SILTY, SLIGHTLY GRAVELLY TO GRAVELLY, DENSE, SLIGHTLY MOIST TO MOIST, RED. GRAVEL (CM); SANDY, SILTY, COBBLES. DENSE, SLIGHTLY MOIST, GREY. F i ÐRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE DRTVE SAMPLE, 1 5/8-|NCH t.Ð. SPLIT SPOON STANDARD PENETRATION TEST AA,/1J DRIVE SAMPLE BLOW COUNT. INDICATES THAT 63 BLOWS OF A 14o-POUND HAMMER FALLING 30 INCHES WERE REQUIREB TO DRIVE THE SAMPLER 12 INCHES. t PRACTICAL AUGER REFUSAL. NOTES 1. THE EXPLORATORY BORINGS WERE ÐRILLED ON MARCH 23,2021 WITH A 4_INCH-DIAMETER CONTINUOUS-FLIGHT POWER AUGER. 2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY TAPING FROM FEATURES SHOWN ON THE SIÏE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE OBTAINED BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLÂN PROVIDED. 4. THE EXPLORATORY BORING LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY ÏHE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MAÏERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTEREÐ IN THE BORINGS AT THE TIME OF DRILLING. 7. LABORATORY TESÏ RESULTS: Wc = WATER CONTENT (%) (ASTM D2216); DD = DRY DENSITY (PCf) (ASTM D2216); +4 = PERCENTAGE RETAINED ON NO, 4 SIEVE (ASTM D6913); -200= PERCENTAGE PASSING N0. 200 SIEVE (ASTM Dl140). Kumar & Associates LEGTND AND NOTES Fig.321 -7 -202 SAMPLE OF: Sond ond Silt FROM:Boringl@20' WC = 8.1 %, DD = 142 pct -2AO = 57 % NO MOVEMENT UPON WETTING ñ JJ L!,Èln I z.o =â Jolnz.o(J 1 0 -1 2 -3 -4 APPLIED PRËSSURE - KSF IO 4 JJ lJJ =tn I zOtr tt =olnzo 3 2 1 o -t t.0 APPLIED PRESSURE - KSF SAMPLE OF: Slighily Sondy Silt qnd Cloy FROM:Boring2 e^20' WQ = 7,0 %, DD = 113 pcf -2AA = 88 % lorted, lnc. Sv.ll EXPANSION UNDER CONSTANT PRESSURE UPOà{ WETTING 21-7 -202 Kumar & Associates SWILL-CONSOLIDATION TEST RESULTS Fig.4 HYDROVETER ANALYSIS SIEVE ANALYSIS IIVE REÆINGS 24 HRS 7 HFS avtN fu¡N U.S. SIANDÑD SERIES CLüR SOUARE OPENINOS ! / J / I I i a I 100 90 Êo 70 GO 60 40 JO 20 IO o l0 30 40 50 60 70 60 90 100 .o13 ,125 2-O OF PARTICLES IN MILLIMETERS 1á2 CLAY TO SILT COBBLES GRAVEL 44 % SAND LIQU¡Ð LIMIT SAMPLE ôF: Sllly Grovefly Sond 42% PLASTICITY INDEX SILT AND CLAY 14 % FROM: Boring 1 @ 4' to 7' ro0 90 60 7A 60 50 40 30 10 o o 10 20 30 10 50 60 70 ao s0 100 2- b f .oot .oo2 .005 .oo9 9,5 !4. r 76,2 127,42s 2.O OIAMETER OF PARTICLES IN MILLIMETERS CLAY TÔ SILT COBBLES GRAVEL 13 % SAND LIOUID LIMIT SAMPLE OF: Silly Grovolly Sond 58 % SILT AND CLAY PLASÏICITY INDEX FROM: Boring 2 @ 7.5' la 10' 29% Tholr l6rt rusulls opply only lo lh! sqmplo! wh¡ch worc l6sled. Thr l€sllng reporl rhqll nol b€ reproduccd, €xc€pf ln f!ll, wtlhoui thê wrlllen qpprovol of Kums. & Åggoclolss, lno. Si€v€ onolys¡s lssl¡rg ls porlormed ìn oceordoncs w¡th ASTM D69f3, ASTM D7928, ASTM C156 End,/e. AS'M Dl140, SAND GRAVEL F¡NE COARSEFINEMEDTUM ICOARSE SIEVE ANALYSISIlYDROMflER ANA¡-YSIS CLËAR SQUARE OPENINGSTIMÊ R¡ÀDI}¡6S 7 tRS24 hñS tâ II.S. SIANDARD SERIES ¿âô ¿¿ô ¿lÕ ¡t6 ¡io I I I / , ! 1 ¡ SANO GRAVEL MEDIUM COARSE FIN E COARSEFIN E 21 -7-202 Kumar & Associates GRADATION TTST RTSULTS Fig.5 I(t \ijffi,?ffillËffi,rÊ;n**'TABLE 1SUMMARY OF LABORATORY TEST RESULTSNo.21-7-202Silty Gravelly SandSilty Gravelly SandSlightly Sandy Silt andClay88132958JI12tJII1.02,07.057Yz &, l0201SOIL TYPEUNCONFINEDCOMPRESSIVESTRÊNGTH(osf)ATTERBERG LIMITSPLASTICINDEX(ololUQUID LIMIT(%lPERCENTPASSING NO.200 stÊvEGRADATIONSAND(%)GRAVEL(%)NATURALDRYDENSÍTYlpcf)NATURALMOISTURECONTENTMISAMPLE LOCATIONDÊPTHlffìBORING42t0244ISilty Gravelly SandSand and SiltSilty Gravelly Sandl457291.58,13.44 &,12010