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Home My WebLink AboutSubsoils Report for Foundation Design|(*n f:,"*r,}ffitrK:f*,{;d'*"' &n Smployee Swtr*d esrnsa$y 5020 County Road 154 Glenr.vood Springs, CO 81{r0l phonc: (970) 945-7988 l'ax: (970) 945-8454 email : kagienn,ood(l4l<unarusa.coln tt'wtv.kuntaru sa. ctln.t Oftice Locations: l)enver (HQ), Parker', Colorado Springs, Forr Collins, Glenwoocl Springs, and Sunlnit Coulty, Colorado September 4,2024 Kent Olson P.O. Box 455 Rifle, Colorado 81650 kent(@k5 -construction. com Subject: Project No. 21-7-356.,{ Subsoil Study for Foundation Design, Proposed Residence, 2607 county Road 314, Garfreld County, Colorado Kent As requested, Kumar & Associates, Inc. has updated the previous subsoil study information collected at the subject site for design of foundations at your proposed building site. The update was conducted in general accordance with our agreement for geotechnical engineering services to you dated February 16,2024. The data obtained for the previous study and our recommendations based on the current proposed construction and the subsurface conditions encountered are presented in this report. Proposed Construction: The proposed residence will be a single-story modular structure of about 1,600 square feet in size and located in the area of Boring 1 shown on Figure l. Ground floor will be above crawlspace. Cut depths are expected to be relatively minor and in the range of 2 to 3 feet. Foundation loadings for this type of construction are assumed to be relatively light 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 proposed building site (Boring 1) consists of an irrigated pasture along County Road 314 as shown on Figure 1. The ground surface slopes gently down to the southwest with minor elevation difference across the assumed building area. Subsurface Conditions: The subsurface conditions at the current proposed residence site were evaluated by drilling one exploratory boring (Boring 1) at the approximate location shown on Figure 1. The logs of the borings drilled throughout the property are presented on Figure 2 with the legend and notes shown on Figure 3. The subsoils encountered at Boring 1, below about one-half foot of topsoil, consist of silty clayey sand with gravel. Results of swell-consolidation testing performed on relatively undisturbed drive samples of the sand soils taken from Boring 1, presented on Figures 4 and 5, indicate low compressibility under existing moisture conditions att S-\.s) N \sa and light loading and moderate compressibility when wetted and additionally loaded. The laboratory test results are summarized rn Table 1. Free water was encountered in Boring I at a depth of about 1,7% feet and the upper soils were moist. Foundation Recommendations: Considering the subsoil conditions encountered in Boring I and the nature of the proposed construction, we recommend spread footings placed on the undisturbed natural sand soil designed for an allowable soil bearing pressure of 1,500 psf for support of the proposed residence. The sand soils tend to compress after wetting and there could be post-construction foundation settlement of around I inch. Footings should have a minimum width of 18 inches for continuous walls and2 feet for columns. The topsoil and loose disturbed soils encountered at the foundation bearing level within the excavation should be removed and the footing bearing level extended down to the undisturbed natural soils. We should observe the soils exposed in the completed foundation excavation for bearing conditions. Exterior footings 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 should be heavily 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 be designed to resist alaterul earth pressure based on an equivalent fluid unit weight of at least 50 pcf for the on-site sand soil as backfill- Floor Slabs: The natural onsite soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade 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 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. A minimum 4-inch layer of relatively well graded sand and gravel such as road base should be placed beneath interior slabs for support. This material should consist of minus 2-inch aggregate with less than 50% passing the No. 4 sieve and less than l2o/o passing the No. 200 sieve. All fiIl materials for support of floor slabs should be compacted to at least 95oh of maximum standard proctor density at a moisture content near optimum. Required fill can consist of the onsite sand soils devoid of vegetation, topsoil and oversized rock. Underdrain System: We understand the proposed finished floor of the residence will be above the surrounding grade and the crawlspace will be relatively shallow. Therefore, a foundation drain system should not be needed with proper backfill placement and positive surface grading' It has been our experience in mountainous areas that local perched groundwater can develop during times of heavy precipitation or seasonal runoff. Frozen ground during spring runoff can create a perched condition. We recommend below- grade construction, such as retaining walls Kumar & Associates, lnc. o Project No. 21-7.356'A a-J- and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain and wall drain system. If the finished floor elevation of the proposed structure is revised to have a floor level below the surrounding grade, we should be contacted to provide recommendations for an underdrain system. All earth retaining structures should be properly drained. Surface Drainage: 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 avoided during construction. 2) Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95o/o 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 6 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 of all backfill. 5) Landscaping which requires regular heavy irrigation such as sod should be located at least 10 feet from the building. 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 recommendations submitted in this report are based upon the data obtained from the exploratory borings drilled at the locations indicated on Figure 1 and to the depths shown on Figure 2,the proposed type of consttuction, 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 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 identified at the exploratory pits and variations in the subsurface 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 at once so 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 Kumar & Associates, lnc, o Project No. 21-7-356.A -4- should provide cc,ntinued consultation and field services durtng construction to review and rnonitor the implementation of our recommendations, and to verify that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or rnodifications to the recommendations presented herein. We recommend on-site observation of excavations and foundation bearing strata and testing of structural filI by a representative of the geotechnical engineer. If you have any questions or if we may be of fiirther assistance, please let us know. Respectfully Submitted, Kummr & &mw*m$mt*su lxt#. Steven L. Pawlak, P. Rev" by: RLD SLPlkac Attachments: Figure 1 '- Location of Exploratory Borings Figure 2 * Logs of Exploratory Borings Figure 3 * Legend and Notes Figures 4 through T - Swell-Consoliclation Test Results Figure 8 - Gradation Test Results Table 1 * Summary of Laboratory Test Results 6 5222I KxEx*r & Ao***iat**, latc. i f*r*rj**t S*. #"1-?-*$S.& ,n:rca,t)ry %oo '4 o BORING 2 4i r-,>a rfi, '(ra ; -- n;,_ ! iq,.,; : ., , ,r\ .. BORING 1 fi:,- .*J da'. '^+ .r Ii a SORING 5 * 100 200 APPROXIMATE SCALE_FEET Fig. 1LOCATION OF EXPLORATORY BORINGSKumar & Associates21 -7 -356 BORING 1 BORING 2 BORING 3 0 1s/12 WC= 1 5.7 DD=1 1 5 -200=89 LL=44 Pl=29 24/ 12 WC= 1 0.9 DD=110 -2OO=82 7/12 11/12 WC=9.5 DD= 1 02 -2OO=43 2s/ 12 WC= 1 2.0 DD= 1 06 5 26/ 12 WC= 1 5.0 DD= 1 05 5 50/4 WC=7.3 47/12 WC=15.9 DD=115 LL= 55 Pl =39DD=118 10 10 16/12 50/2 38/ 12 WC= 1 8.7 DD= 1 08 F trJtil LL ITFo- trJo 15 15 F[Jl-! LL I-F L trJo 7/12 50/ 4 50/4 a_zt - 20 20 6/ 12 50/2 61 /12 25 25 13/ 12 30 30 4e/ 12 WC=3.4 DD= 1 31 -200= 1 5 20/ 12 WC=5.6 DD= 1 09 WC= 1 1.1 *4=14 -200=30 21 -7 -356 Kumar & Associates LOGS OF TXPLORATORY BORINGS Fig.2 LEGEND TOPSOIL; SANDY CLAY, ORGANICS, MEDIUM STIFF, M0lST, DARK BROWN CLAY (CL) SANDY, VERY STIFF, SLIGHTLY MOIST, BROWN, CALCAREOUS sAND (SC-SM) CLAYEY, SILTY, WITH GRAVEL, LOOSE TO MEDIUM DENSE, MOIST, LIGHT BROWN, CALCAREOUS. sAND (SM) StLTy, W|TH ANGULAR GRAVEL, DENSE TO COARSE, SLIGHTLY MOIST TO Mo|ST, LIGHT BROWN TO BROWN. SANDSTONE BEDROCK, HARD, SLIGHTLY MOIST, TAN - t:f lV] WEATHERED CLAYSTONE, HARD, SLIGHTLY MOIST, GRAY AND BROWN DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE i DRTVE SAMPLE, 1 3/8-INCH l.D. SPLIT SPOON STANDARD PENETRATION TEST. - I. ^ DRIVE SAMPLE BLOW COUNT. INDICATES THAT 7 BLOWS OF A 14o_POUND HAMMER '/ '' FALLTNG JO TNCHES WERE REeUIRED TO DRIVE THE SAMPLER 12 INCHES. 4 oTpTH To WATER LEVEL AND NUMBER oF DAYS AFTER DRILLING MEASUREMENT WAS MADE 2> oeplu AT WHIcH BoRING cAVED AND NUMBER OF DAYS AFTER DRILLING MEASUREMENT WAS MADE. NOTES 1, THE EXPLORATORY BORINGS WERE DRILLED ON MAY 5, 2021 WITH A 4-INCH-DIAMETER CONTINUOUS_FLIGHT POWER AUGER. 2, THE EXPLORATORY BORINGS WERE LOCATED BY THE OWNER' 3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE NOT MEASURED AND THE LOGS OF THE EXPLORATORY BORINGS ARE PLOTTED TO DEPTH. 4. THE EXPLORATORY BORING LOCATIONS 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 LEVELS SHOWN ON THE LOGS WERE MEASURED AT THE TIME AND UNDER coNDlloNS tNDicATED. FLUcruATtoNS rN THE wATER LEVEL MAY OccuR wlTH TIME. 7. LABORATORY TEST RESULTS: wc = wATER CONTENT (%) (ASTM D2216): DD = DRY DENSITY (PCf) (ASTM D2216); +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ASTM D6913); _2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D11AO); LL = LIQUID LIMIT (ASTM D4318); PI = PLASTICITY INDEX (ASTM 04518). 21 -7 -356 Kumar & Associates LTGEND AND NOTES Fig.3 ;r.': tir SAMPLE OF: Silly Cloyey Sond FROM:Boringl@2.5' WC = 9.3 %, DD = 102 pcf -2OO = 43 % ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING be in full, Sw6ll Con6olidotion D-4546. be JJ tlJ =a I z.otr o)oaz.oO 0 -1 -2 -3 -4 -5 -6 APPLI PRESSURE -10 100 Fig. 4SWELL_CONSOLIDATION TEST RTSULTSKumar & Associates21 -7 -356 * "1 ;; .':: SAMPLE OF: Silty Grovelly Sond FROM:Boringl@7.5' WC = 5.6 %, DD = 109 pcf NO MOVEMENT UPON WETTING x JJt! =UI I z.otr o =o U)zo(J 0 -1 -2 -3 -4 APPLIED PRESSURE - KSF 10 100 4 )q JJ LJ =a I z.o F o =oaz.oo 5 2 1 0 -1 -2 1.0 PLIED PRESSURE _ KSF t0 SAMPLE OF: Sondy Clcy FROM:Boring2@4' WC = 1 5.O %, DD = 105 pcf EXPANSION UNDER CONSTANT PRESSURE UPON WETTING in of tcat rcsults tcstcd. frc without th3 writtln 21 -7 -356 Kumar & Associates SWELL_CONSOLIDATION TEST RESULTS Fig.5 a :,..2 :i]; , ':.: SAMPLE OF: FROM: Boring WC = 7.3 % 2@7' DD = 118 pcf Sondslone NO MOVEMENT UPON WETTING )s JJ LJ =@ I zotr o -lotnz.oO 1 0 -1 -2 -3 -4 1.0 APP PRESSURE - KSF 10 100 4 x JJItl =a I zotr o =oazoo 5 2 1 0 -1 1.0 PLIED PRESSU - KSF l0 100 SAMPLE OF: Sondy Cloy FROM:BoringS@4' WC = 1 2.O %, DD = 106 pcf EXPANSION UNDER CONSTANT PRESSURE UPON WETTING to the i6 Sw6ll in test 21 -7 -356 Kumar & Associates SWELL_CONSOLIDATION TEST RESULTS Fig. 6 { ':1 t: ii SAMPLE OF: Sondy Cloy FROM: Boring 3 @ 10' WC = 1 8.7 %, DD = 108 pcf EXPANSION UNDER CONSTANT PRESSURE UPON WETTING in6xc€pt Sw6ll D-4546. ft6 only to th6 6 5 4 )q J.Jtd =a t zo F cl =ov)zo c.) 5 2 1 0 -1 -2 1.0 D PRESSURE -'t0 100 21 -7 -356 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig.7 6 H 100 90 ao 70 60 50 ao 50 20 HYDROMETER ANALYSIS SIEVE ANALYSIS TIME REAOINGS CLEAR 7 HRS 0 lo 20 to 40 50 6o 70 60 90 100 - '1 .ool .o37 ,o73 I -125 i 2.aa 2.O 1.75 9.5 DIAMETER OF PARTICLES IN MILLIM CLAY TO SILT COBBLES GRAVEL 11 % SAND LIQUID LIMIT SAMPLE OF: Grovelly SiltY Sond 56% PLASTICITY INDEX SILT AND CLAY 30 % FROM: Boring 1 (l 10' & 15' (Comblned) GRAVELSAND COARSE FINE COARSEFINEMEDIUM Thos6 l€sl rcsulls qpply only lo lh6 somDles which were lesled. The fetifio report 3holl nol bo rcproduc€d, "xceoi ln full. wllhoul lh€ wrltlsn ooorbvol of Kumor & As3ociqlos, lnc. Sie've onolvsls lolllnq l! per{grmod ln """o.aonc6 wlth AST=M 06913' ASTM D7926' ASTM C156 ond/or ASTM Dll'+0. Fig. 8GRADATION TEST RESULTSKumar & Associates21 -7 -356 K*n Xsnnr & *esaciate$, lnc"o Geo:echlical and Materia's Engireers and enviranmental $cieniists TABLE 1 SUMMARY OF LABORATORY TEST RESULTS No.21-7-356 Sandy Clay Sandy Clay Sandy Clay Sandy Clay Silty Gravelly Sand Gravelly Silty Sand Sandy Clay Sandy Clay Sandstone SOILWPE ATTERBERG LIQUID LIMIT UNCONFINED COMPRESSIVE STRENGTH PLASTIC INDEX Silty Clayey Sand Silty Gravelly Sand 39 29 55 44 82 30 89 43 5I PERCENT PASSING NO. 200 stEvE 56l4 106 115 108 105 118 110 115 IaJ1 109 GMDATION NATURAL DRY DENSITY SAND f/"1 GRAVEL (%) r029_3 18.7 10.9 12.0 15.9 rs.7 15.0 I --) 5.6 I 1.1 3.4 01 1 4 7 1 4 7 10&ls combined 7t/, NATURAL MOISTURE CONTENTBORING LOCATION DEPTH J 2 1 2y, 5