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Home My WebLink AboutSubsoils Report for Foundation Designt(+ril An Employcc Oryned Compony 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@kumarusa.com www.kumarusa.com rOffioe fi,ocatiorûs: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and SummitCormty, Colorado August 23,2023 Lauren Vance 3194 CountyRoad226 Silt, Colorado 81652 lauren@truenorthcolorado.com Project No. 23-7-117 Subject: Subsoil Study for Foundation Design, Proposed Shop Building,3194 County Road226, Garfield County, Colorado Dear Lauren: As requested, Kumar & Associates, Inc. performed a subsoil study for design of foundations at the subject site. The study was conducted in accordance with our agreement for geotechnical engineering services to you dated January 16,2023. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presented in this report. Proposed Construction: The proposed shop will be a tall, one-story steel-frame, metal skin structure, 30 feet by 40 feet in plan size, located on the site as shown on Figure 1. Ground floor will be slab-on-grade. Cut depths are expected to range between about 1 and 3 feet. Foundation loadings for this type of construction are assumed to be relatively light to moderate and typical of the proposed type of construction. If building conditions or foundation loadings are significantly different from those described above, we should be notified to re-evaluate the recommendations presented in this report. Site Conditions: The barn site is currently vacant with around 3 feet of compacted road base placed on it. The site is relatively flat and the area around the proposed shop is vegetated with grass and weeds with scattered brush. The property is developed with a2-story wood frame house located about 75 feet southwest of the proposed barn site. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating two exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. The subsoils encountered, below about Yzfoot of topsoil, consist of weathered to relatively hard claystone bedrock of the Mancos Shale Formation. Results of swell-consolidation testing performed on relatively undisturbed samples of the shale, presented on Figure 3, indicate low compressibility under existing moisture conditions and light loading and a low expansion potential when wetted. No free water was observed in the pits at the time l(rilw&ilmdates, lns.' Geotechnical and Materials Engineers and Environmental Scientists ll exca was Foundation Recommendations: Considering the subsurface conditions encountered in the exploratory pits and the nature of the proposed construction, we recommend spread footings placed on the undisturbed weathered shale designed for an allowable bearing pressure of 4,000 psf for support of the proposed shop building. The claystone bedrock tends to expand -2- after wetting and there could be some post-construction foundation movement. Footings should be a minimum width of 16 inches lirr continuous walls and 2 t'eet t'or colulnns. 'l'he topsoil and Ioose tlisl.urbctl soils shoultl be removed in fooLing areas. The existing fill encuutttered at the foundation bearing level could be evaluated for compaction or removed and the footing bearing level extended down to the undisturbed natural claystone. Compaction of structural fill should be at least 98% of standard Proctor density. bxterior fbotings should be provided with adequate cover above their bearing elevations for frost protection. Placement of footings at least 36 inches below the exterior grade is typically used in this area. Continuous foundation walls (if any) should be reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 10 feet. Foundation walls acting as retaining structures (if any) should be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 55 pcf for the on-site soil as backfill. Floor Slabs: The compacted structural fill should be suitable to support lightly to moderately loaded slab-on-grade construction. To reduce the efIècts of some differential movemento floor slabs should be 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 for joint spacing and slab reinforcement should be established by the designer based on experience and the intended slab use. All fill materials for support of floor slabs should be compacted to at least95%o of maximum standard Proctor density at a moisture content near, to slightly over optimum. Required fill should consist of a suitable imported granular material such as '/c-inch road base. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the shop has been completed: l) Inundation ofthe foundation excavations and underslab areas should be avoided during construction. Drying could increase the expansion potential of the claystone bedrock. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95Yo of the maximum standard Proctor density in pavement and slab areas and to at least 90% of the maximum 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 slope of 12 inches in the frrst l0 feet in unpaved areas and a minimum slope of 3 inches in the first l0 feet in pavement and walkway¿reas. 4) Roof downspouts and drains should discharge well beyond the limits oiall backfill. 5) Landscaping which requires regular heavy irrigation should be located at least l0 feet from the building. Consideration should be given to the use of xeriscape to limit potential wetting of soils and weathered bedrock below the foundation caused by inigation. Kumar & Associates, lnc. o iPqioctflo. ß:l;tr17 -3- r fftations: This shdy has beeri conducted in accordance with generally accsodædofuical agineering principlæ and practices in this area at this time. We make no warrd5r €ilh€r €qress or implid. The conclusions and recommend¿tions submitted in this reput ae basod rrymthe data obtained from the exploratorypits excavated althe locations indicedmFigwu f mdto the depths shown on Figure 2, thep'roposed qpe of construction, and orrerçsiæin fte area. Our services do not include detemrining the ¡nesence, prevention or poeffiit¡r¡rfmld or úer biological contaminants (MOBC) developing in the future. If the client is mønod about MOBC, then a professional in this special field ofpractice should be consr¡ltsd- Our firrlings include interplation and extrapolation ofthe subsurface conditions ideilifiod dfrG eaqilmatory pits and variations in the zubsurface conditions may not become eviddMil sxcavation is performed. If conditions encountered during construction appemdiffurdftrm lûose desqibed in this report we should be notified at once so re-evaluation offu rmmendations may be made. This re,port has been prepared for the exclusive use by or¡r client for design purpofrcs- V/e æe mt reryonsible for technical interpretations by others of our infor¡ration. As the pmjectcrrolvæ, we úmld provide continued conzultation and field services during construction to rcnicnv md mmitor the implementation of orr recommend¿tions, and to v€riry that the ræmmddions havcbeen appropriately interpreted. Significant design changes may rquire addirimal analJËi$ mmdifications to the recommendations presented herein. We recommend on-sife obeør¿rdim ofexcavations and foundation bearing shata and testing of structural fill by a represcddive of ûe geotechnical engineer. If)rou have any questions or ifwe may be of firther assistance, please let us knour" ncryectfully Submitted, Kumar & Associates, lnc. Ilmiel E. Hardin, P.E. Røviewed by: Steva L. DEl{ltcac dtærments of Exploratory Pits Figure 2-I-oç of Exploraúory Pits Figure 3 - Swell-Consolidation Test Results Table I - Summary of Laborctary Test Results ! o ßm Kumar & Associates, lnc. o Project No. 23-7-117 LOTA çMTNWOfi L MrNOß SUtDWng@N Fø.tNøNto-sß.@ø.R"&. lrÆL!'ffi)P{AStÍtrC CAP U '59'E 396.95'"Vfint) {.4_ 396.58' PIT PIT 1 o ffi,,v" 2 o ; zI|{t )¿ e¿{g -Du{ e¿(s !€z z.6)aa s{¡ H @(ï !f{ - ã ro (\¡ H ,i' PllÁÃT=Stagzß' 3 I" W V ø "${t' sE9-O833 69.97' fütMÐ W..s ßJfa#iß" & 1 -7[4"' WL]-6ñ) NASTTACÁP oLWqßW) 3194 COUNTY ROAD 226 LA'xWÍÍqM@, " ;--:::- - . - lrütùtÐ^m"sre. flASII(- 2002040 APPROXIMATE SCALE-FEET F(Ì) jFlr co aU(â 5ö' ,{ü(lo e)(,tr ùll-g Jg 4E (s)6 /4t2-6, CTSTERN (4.ooo ØL.)6ì,/- \1 / ^Grt' +TOP OF FOUNDATION WALL ASSUMED 1OO.O FEET. 3 îryO?OSED sfioP t- 23-7 -1 17 Kumar & Associates Fig. 1LOCATION OF EXPLORATORY PITS E EI: I PIT 1 EL. 98, Pt't 2 EL. 98.5' 0 0 WC= f 0.4 DD= 1 08l-- LJtrtt! I-t--fLIJo 5 WC=11.3 DD=1 1 6 5 t-til tJJ LL ITF(L t¡J É) 10 10 LEGEND NI F TOPSOIL; SLIGHTLY SANDY CLAYEY SILT, ORGANICS, ROOTS, FIRM, SLIGHTLY MOIST' BROWN. CLAYSTONE; WEATHERED TO HARD WITH DEPTH, RELATIVELY FLAT BEDDING, MANCOS SHALE FORMATION. HAND DRIVE SAMPLE. NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON AUGUST 11,2023 2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE MEASURED BY HAND LEVEL AND REFER TO THE TOP OF FOUNDATION WALL AS 1OO FEET, ASSUMED. 4. THE EXPLORATORY PIT LOCATIONS AND ELEVATIONS SFIOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF EXCAVATION. PITS WERE BACKFILLED SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSITY (pcf) (ASTM D 2216). 23-7-117 Kumar & Associates LOGS OF EXPLORATORY PITS Fig. 2 I 2 1 0 1 2 -5 -4 1 JJ l¿l =.0 I zo -l o =oUtıZ-zo(J -5 àq JJl¡¡ =Ø I zo F ô Jolnzo C) I I.O APPLIED 1.0 APPLIED PRESSURE - KSF 10 SAMPLE OF: Wcothcrcd Cloyslonc FROM:Pit1O2.5' WC = 10.4 )1, DD = 108 pcf \ EXPANSION UNDER CONSTANT PRESSURE UPON WETTING {) \) SAMPLE OFr Cloyolono FROM:Pit2O4.5' WC = 11.3 %, DD = 116 pcf EXPANSION UNDER CONSTANT PRESSURE UPON WETTING I \¡ ]rtmffioÞY6Ybhmpb hd. th. t-lh¡ rpo.t#l mt h npEdurd, rMrt h full, tlüod lh. rrlbn opÊwl ofl(umr .ñd ^Þclob. hc. Sr.llCoülttatloí t-tho Fdtu lnñ6úñm rlh ^W lì.ffi t00 23-7-117 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 5 E n I l(+lt#ffiåmm*$ü*" - TABLE 1 SUMMARY OF LABORATORY TEST RESULTS No.23-7-117 ATI LttllssaltPlLOCATIONGRADATION t%ì PLASTIC ti¡DEx lhrñ EXPANSION PRESSURE EXPAI¡SION lo/^\ SOII TYPE tol"t NATURAL t0tsfuRE COI{TENT NATURAL DRY DENSITY ln.rlì GRAVEL (%) SAND (%) PERCENT PASSI¡G N0. 200 stEvE l%t LIQUID LITfÍPll tfit DEPTI{ 3,000 1.3 Weathered ClaystoneI2Y,10.4 108 2,500 0.5 Claystone24%I 1.3 116