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Home My WebLink AboutSubsoils Report for Foundation DesignHEPWORTH . PAWLAK GEOTECHNICAL i j 'l!\'15 August 2,2006 Red House Architecture Attn: Bruce Barth 815 Blake Steet Gie,nwood Springs, Colorado 81601 Hepworth-Pawlak Geotechnical, Inc. 5020 Counry Road 154 Glenwood Springs, Colorado 81601 Phone: 970"945.7988 Fax:9'10-945-8454 email hpgeo@hpgeotech.com Job N<.r.106 0676 H $5't'f:'$lt':.\ \ \\\s Subject: DearMr. Barth: As requested, Hepworth-Pawlak Geotechilic al,Iac.performed a subsoil study for design of foundations at the subject site. The studywas conducted in accordance with our agreement for geotechnical engineering s€rvices to Red House Architecture dated luly 27, 2006. The data obtained and our reoommendations based on the proposed construction and subsurface conditions encountered are presented in this report' Hepworth-Pawiak . Geotechnicai, Inc. previously conducted apreliminary geotechnical study for the subdivision development and presented our findings in a report dated February 28,2003, Job No. 103 115. proposed Construetion: The proposed residence will be a one story wood frarne structure located on the site as shown on Figure 1. Ground floor will be structural over a crawlspace for the residence and slab-on-grade in the garage. Cut depths are expected to range between about 3 to 4 feet. Foundation loadings for this type of cnnstruction are assumed to be relatively light and typical of the proposed t51pe of construction' Ifbuilding conditions or foundation loadings are significantly different frorn those described above, we should be notified to re-evaluate the recommendations presented in this report. - '-Site Condiddns: -The-Sitb was-viicar*t dfthe finioofotlr-fie-ld explora-t1'otl; Thd Elt'oirnd" surface is relatively flat with'.a slight slope down to the south and less than about 2 feet of elevation difference across the building area. A driveway was being constructed into the building area from Coulter Creek fudge Road located to the northeast at the time of the Subsoil Study for Foundation Design, Proposed Moak Residence, Lol L2, Ranch at Couiter Creek, Coulter Creek Ridge Road, Garfield County, Colorado. - -ae .s a\ \ parker 303.841.7119 ' ColoradoSprincs 7t9-633-5562 o Silverthome 970-468.1989 -2- fie1d exploration. Vegetation consists of grass and weeds with scattered pinon and junipcr trccs and scruboatrr to the south of the building area' Subsurface Cuntlitious: Tire subsurfacc conditions at tho sito were evaluated by excavating two exploratury piis. at the approxlmate locations shown on FlgUre I ' The logs of the pits are presented on Figure 2. The subsoils encountered, below about 1% ta 2 feet of topsoii, consist of stiffto very stifi sandy silfy clay, Relatively dense, siity sand and gravel with cobbles and small boulders was encountered beneath the clay tnPit I at a depth of SYzfeet. Scattered lenses of silty sand and gravel were encountered within the clay soils tnPit2. Results of swell-consolidation testing performed on relatively undisturbed samples of the clay soils, presented on Figures 3 and 4, generally indicate low to moderate compressibilify under conditions of loading and wetting. Two of the sampies tested showed a low expansion potential when wetted under a constant light srrcharge. Results of a gradation analysis perfcrrned on a sample of sand and gravel (minus 3 iach fraction) obtained from thc site are preseiited on Fig:urc 5' No free vrater was observed in the pits at the time of excavation and the soils were slightly moist. Foundation ftssgmmendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, we recornrne,nd spread footings placed on the undisturbed natural soil designed for an allowable soil bearing pressure of 000 psf for support of the proposed residence. The clay soils have variable settlement/ heave after wetting and there couid be up to about 1 inchof post- construction foundation movement. The expansion potential of the.subgrade should be further evaluated at the time of construction. Footings shouid be a minimutn width of 16 inches for continuous walls and2 feet for coiumns. Loose and disturbed soiis encountered at the foundation bearing level within the excavation should be removed and the footing bearing level extended down to the undisturbed nafural soils. Exterior footings should be provided with adequate cover above theirbearing eievations for frost protection. Placement of footings at least 36 inc,hes beiow the exterior grade is typically used in this area. Continuous foundation walls should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length oiat least 12 ieei. . 7-L:--- ,,,^rr^ ^^+.:-* ^^ *^+^.i*i-c.ofrqrnfrrre+oharrld he-rlesirtnerj|-tn rgSiSt a{atefal gafthli ounoaLluil walls-aul.l;uB-as lt't4IIIuIS DlILrvllrr!o olrvuru vv uvsrbl^v pressgre based on an equivalent fluid unit weight of at least 55 pcf for the on-site soil as backfill. Job No.106 0676 c&Ftecrr -3- Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade conskuction. The settlement/heave potential of the subgrade should be further evaluated at the time of construction. To reduce the effects of some differential movement, floor slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab conffol joints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. A minimum 4 inchiayer of sand and gravel, such as road base, shouid be placed beneath interior slabs-on-grade for subgrade support. This material should consist of minus 2 inch aggregate with less than 50% passing the No. 4 sieve and less than T}Vopassrngthe No' 200 sieve. Ajl fil1 materials for support of floor slabs should be comp acted to at least 95Vo of maximum standard proctor density at a rnoisture content near optimum, Required fill can consist of the on-site soils devoid of vegetation, topsoil and oversized rock. underdrain system: Although groundwatef was not encountered during our expioration, it has been our experience in the areas and where ciay soils arepresent, that local perched groundw ater candevelop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoffcan create a perched condition- Therefore, we reco11lmend below-grade construction, such as crawlspace areas, be protected frorn wetting by an underdrain syste,m. The drain should also act to prevent buildup of hydrostatic pressuros behind foundation walls' The underdrain system should consist of a drainpipe surrounded by free-draining granular material placed at the bottom of the wall backfill. The drain lines should be placed at each level of excavation and at least 1 foot below lowest adjacent finish grade, and sioped at a minim.,tm 1,% gradeto a suitable gravity outlet. Free-draining granular material used in the drain system should consist ofminus 2 nchaggregate with less than S}o/opassing the No. 4 sieve and less than2%opassing the No. 200 sieve. The drain gravel should be at least 1%feetdeq. Job No. I 06 0676 ceFtecrr -4- Surface Diainage: The following 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 avgidcd dururg construction. Drying could increase the expansion potential ulthe claY soils. Z) Exteriorbackfill should be adjusted to near optimum moisfure and compacted to at least 95% af the maximum standard Proctor densily in pavement and slab areas and to at least 90Yo of themaximum standard Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum siope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in pavement and walkwaY areas. 4) Roof downspouts and drains should discharge well beyond the limits cf all backfill. 5) i:rigation sprinkler heads'and landscaping which requires regular heavy irrigation, such as sod, should be located at least 5 feet from foundation wails. Limitations: This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this area at this time. We make no warranty either express or implied. The conclusions and recornmendations submitted in this report are based upon the data obtained from the exploratory pits excavated at the locations indicated on Figure 1 and to the depths shown on Figure 2, the proposed type of construction, and our experience in the area. Our servioes do not include determining the presence, prevention or possibility of moid or other biological contaminants (MOBC) deveioping in the futurs. lf the client is concerned about MOBC, then a professional in this special field of practice should be consulted. Our findings include interpolation and exhapolation of the subsurface conditions identified at the exploratory pits and variations in the subsurface conditions may not become evident until excavation is performed. if . .- a:Lt +^*^J ,i,,.-.l-c nnno*a:nf,in- cnneet- di.fFer:ent .frnr.n-fhose.desct'ihed.in.thiS-cionultIgIIs-EI.ILiuLllltEl't cl-tl$l-ll lB rjt,llsLlLre$rvrr 4yyvq $rlrvavrr! report, we should be notified at once so re-evaluation of the recommendations may be made. Job No.l06 0676 c&Btear -5- This report has been prepared for the exclusive use by our client for design putposes- We are not responsible for techtrical interpretations by others of our information. As the project evolves, we should provide continued consuitation and field services during construction to review and monitor the implementation of our recofilmendations, and to verify that the recorlmendations have been appropriateiy interpreted. Significant design changes may require additional anaiysis or modifications to the recommendations presented herein. We recommend on-site observation of excavations and foundation bearing strata and testing of structural fillby a representative of the geotechnical engineer. If you have any questions or if we maybe of further assistance, please let us know' RespectfullY Submiued, HEPWORTH . PAWLAK GEOTECHNICAL, INC. Jordy Z. Adamson, Jr., P.E. Reviewed bY: Steven L. Pawlak, P.E. IZNvad attachmentsFigurel_LocationofExploratoryPits Figure 2 *Logs of ExPloratory Pits - * - -figures 3-and4- Swel{-Gonsolidation Test-Resutrts Figure 5 - Gradation Test Results' Job No.106 0676 c&Ftecn COULTER CREEK RIDGE ROAD APPROXIMATE SCALE 1" = 60' LOT 13 1 tLOT 11 I PrT2 PROPOSED RESIDENCE I PITl LOT 12 Figure 1LOCATION OF EXPLORATORY PITSd HEFWoxtrI}T 106 0676 PIT 1 PIT 2 U oo LL Ico(l)o 5 o.loIL I .Co 0)a 0 5 10 WC=13.8 DD=85 Ir *4=24| .200=47J WC=16,0 DD:97 10 LEGEND: WC=9.8 DD=96 ToPSolL; sandy silty clay, organics, roots, firm, slightly moist, dark brown' CLAy (CL); silty, sandy, scattered silty sand and gravel lenses in Pit 2, stiff to very stiff, slightly moist, light brown, slightlY calcareous. ffi SAND AND GRAVEL (SM-GM); silty to very silty, with cobbles and small boulders' dense' slightly moist' brown' $ubangular to subrounded rock. 2" Diameter hand driven liner sample' Disturbed bulk samPle' NOTES: 1. Exploratory pits were excavated on July 28,2006 with a caterpiller 320c trackhoe' 2. Locations of exploratory pits were measured approximately by pacing from features shown on the site plan provided. 3. Elevations of exploratory pits were not measured and the logs of exploratory pits are drawn to depth' 4. The exploratory pit locations should be considered accurate only to the degree implied by the method used' S. The lines between materials shown on the exploratory pit logs represent the approximate boundaries between rnaterial types and transitions may be gradual' 6. No free water was encountered in the pits at the time of excavating. Fluctuation in water level may occur with time' 7, Laboratory Testing Results: WC = Water Content (7o) DD: *4:Nb, + bieve -200: Percent Passing N0.200 sieve I I J F I Figure 2LOGS OF EXPLORATORY PITSG6 HEFWOTIT*PI 106 0676 l Moisture Content: 13.8 Dry DensitY = 85 Sample of: Sandy Silty Clay From: Pit 1 at 4 Feet percent pcf No rnovement _upon wetting \ \ ) 0 2 3 4 \o(t\ c .o U)0oLo- EoO 1.0 10 1000.1 APPLIED PRESSURE - KSf 0 2 be Co"6c(6 o-X LU Ico'6ao Eo C) 10 APPLIED PRESSURE - ksf Moisture Content - 16.0 Dry DensitY: 97 Sample of: Sandy Silty Clay From: Pit 2 at 6 Feet percent pcf r-J \) txpansron upon wetting Figure 3SWELL-CONSOLI DATION TEST RESU LTS106 0676 0.1 1.0 100 0 1 2 bsc .9ac(sox LU Ic .9g, tn Eo- Eo CJ Moisture Gontent = LB Dry DensitY : 96 Sample of: Sandy Sitty Clay with Gravel From: Pit 2 at 10 Feet percent pcf \f I ) Ex$ansion upon wetting 't0 APPLIED PRESSUHE - ksf Figure 4SWELL-CONSOLI DATION TEST RESU LTS1 06 0676 0,1 1.0 '100 100 g0 80 70 602 6(n o- 50F tlJ()&IJ40 o- a lrJzaFIJE F.zlrl() E,l! o- TIME FEADIN( S U.5. STANDARD 8ERIES CLEAF SOUAFE OPENINGS o ?* tft, '6flfrx 1 MlN, #200 #100 #50 #30 #16 #a #4 3/8' 3/41' 1112' 3" 5"6" 8n ,60M 10 20 30 40 50 60 70 80 90 100 30 n 10 0 .001 .oo2 .005 .009 .019 .037 .074 '150 .g00 ,600 1'18 2.36 4.75 DIAMFIER OF PAHTICLES IN MILLIMFTERS 9.5 19.0 37.5 12.5 76.2 152 203 127 Figure 5GRADATION TEST RFSI. JLTSGsd HEFWOTTH.PArY 106 0676 CTAYIO SLT GRAVEL 24 O/" LIQUID LIMIT % SAMPLE OF: Very SiltY Sand and Gravel co8BtFs SILTAND CIAY 47 % PLASTICITY INDEX O/O FROM:Pit 1 at B to 10 Feet SAND 29 % G FINEt coAribh)luM