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Home My WebLink AboutSubsoils Report for Foundation Designrcrt lfumar & Associates, lnc. @ Geotechnical and Materials Engineers and Environmental Scientists An Empleyeo Ot*rltsd C*mFsny 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email : kaglenwood@kumarusa.com www.kumarusa.com Office l-ocations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED SECOND STORY AND INFILL ADDITION TO EXISTING RESIDENCE LOT 6o BLOCK 2, MEADOW WOOD SUBDIVTSTON 91 MEADOW WOOD ROAD GLENWOOD SPRTNGS, COLORADO PROJECT NO. 23-7-640 JANUARY 17,2024 PREPARED F'OR: KENDRA HEGLAND 3706 RED BLUFF LANE GLENWOOD SPRTNGS, COLORADO 81601 khesland@me'com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITIONS. FIELD EXPLORATION ........ SUBSURFACE CONDITIONS .... FOUNDATION BEARING CONDITIONS ...... DESIGN RECOMMENDATIONS ......... FOUNDATIONS FLOOR SLABS....... SURFACE DRAINAGE......... LIMITATIONS..... FIGURE 1 - LOCATION OF EXPLORATORY BORING FIGURE 2 -LOG OF EXPLORATORY BORING FIGURE 3 - SWELL _ CONSOLIDATION TEST RESULTS TABLE 1 - SUMMARY OF LABORATORY TEST RESULTS 1 I ., a 2 2 J 4 ......- 4 - I I Kumar & Associates, lnc. @ Project No,23-7'640 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed second story and infill addition to the existing residence located on Lot 6, Block 2, Meadow Wood Subdivision, 91 Meadow Wood Road, Glenwood Springs, Colorado. The project site is shown on Figure 1. The purpose of the study was to develop recommendations for the foundation design. The study was conducted in accordance with our agrsement for geotechnical engineering services to Kendra Hegland dated November 3,2023. A field exploration program consisting of an exploratory boring was conducted to obtain information on the general subsurface conditions. Samples of the subsoils 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 analyzedto develop recommendations for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during this 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 addition will be a single-story above the existing single-story detached garage and infill of the area between the garage and existing residence. We assume relatively light additional foundation loadings and typical of the proposed type of construction. There will be minor or no grading for the addition. 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 existing residence is a single-story wood-frame structure with a detached slab-on-grade garuge located on the site as shown on Figure 1. The residence and garage are apparently founded on shallow spread footings with no signs of excessive settlement and distress reported. The topography at the site is valley bottom with a gentle slope down to the northeast. Vegetation consists oflandscaped grass, aspen, and pine trees. FIELD EXPLORATION The field exploration for the project was conducted on December 27,2023. One exploratory boring was drilled at the location shown on Figure 1 to evaluate the general subsurface conditions. The boring was advanced with 4 inch diameter continuous flight augers powered by Kumar & Associates, lnc. @ Project No, 23-7-640 1 a truck-mounted CME-45B drill rig. The boring was logged by a representative of Kumar & Associates. Samples of the subsoils were taken in the boring with a 2-inch I.D. spoon sampler. The sampler was driven into the subsoils at various depths with blows from a 140 pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-1586. The penetration resistance values are an indication of the relative density or consistency of the subsoils. Depths at which the samples were taken and the penetration resistance values are shown on the Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The subsoils consisted of about 6 inches of topsoil overlying about l5/zfeet of sandy clay to clayey sand underlainata depth of 16 feet by relatively dense, silty sandy gravel with cobbles and possible boulders down to the depth drilled of 17% feet. Drilling in the dense granular soils with auger equipment was difficult due to the cobbles and possible boulders and drilling refusal was encountered in the deposit. T.aboratory testing performed on samples obtained from the boring included natural moisture content and density, unconfined compressive strength, and percent finer than sand size gradation analyses. Results of swell-consolidation testing performed on a relatively undisturbed drive sample of the sandy clay, presented on Figure 3, indicate moderate compressibility under conditions of loading and wetting. No groundwater was encountered in the boring at the time of drilling and the subsoils were moist. FOUNDATION BEARING CONDITIONS The existing residence alrld garage are founded on shallow spread footings apparently bearing on the sand and clay soils encountered at shallow depth in the boring. It should be feasible to provide additional loading to the footings for the addition provided some sefflement of the foundation is acceptable. The structural engineer should review the existing foundation conditions as part of their design. DESIGN RECOMMENDATIONS FOI.INDATIONS Considering the subsurface conditions encountered in the crawlspace and exploratory boring and the nature of the proposed construction, it should be feasible to load the existing spread footing Kumar & Associates, lnc. @ Project N0.23-7-640 -J- foundation bearing on the natural soils to an allowable bearing pressure of 1,500 psf. Any additional (new) foundations should also bear on the relatively stiff natural soils. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed natural soils should be designed for an allowable bearing pressure of 1,500 psf. Based on experience, we expect settlement of footings designed and constructed as discussed in this section will be about I inch or less depending on the loadings. 2) The footings should have a minimum width of 20 inches for continuous walls and 2 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 aTea. 4) Continuous foundation walls should 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 designed to resist a lateral earth pressure coffesponding to an equivalent fluid unit weight of at least 55 pcf for the on-site granular soils as backfill. 5) All existing fill, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the relatively stiff natural soils. The exposed soils in footing area should then be moistened and compacted. 6) A representative ofthe geotechnical engineer should observe any new footing excavations prior to concrete placement to evaluate bearing conditions. FLOOR SLABS The natural on-site 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. 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 the on-site soils devoid of vegetation, topsoil and oversized rock. Kumar & Associates, lnc, @ Project No. 23-7-640 -4- SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the addition 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 95Yo of the maximum standard Proctor density in pavement and slab areas and to at least 90o/o 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 l0 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in paved areas. Free-draining wall backfill should be capped with about 2 feet of the on-site soils to reduce surface water infiltration. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heary irrigation should be located at least 5 feet from foundation walls. LIMITATIONS 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 boring drilled at the location indicated on Figure 1 and the observed crawlspace soils, 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 concerned about MOBC, then a professional in this special field of practice should be consulted. Our findings include 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 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 reconmsndations, and to verify that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis Kumar & Associates, lnc. @ Project No.23-7-640 5 or modifications to the recommendations presented herein. We recommend on-site observation ofexcavations and foundation bearing strata for any new footing areas. Respectfully Submitted, Kumar & Associates, I Robert L. Duran, P.E Reviewed by: b Daniel E. Hardin, P.E. RLD/kac cc: West 40 Studio -Adam Cook M) Kummn & Assoei&tes, Bn*" d Prcj**€ i,l*. 33-?.540 4rd h{lil, hl 6. 9,64k :j. Mo8ddr b EJ ffrl si 35 @ i*oslzlzn€ati' 39ei 6.n' 9A E51i o@o =zc) ,/. 6"o \.f*.; ift 'v) d I .*; i*t;\. $' I "d," -\ I I sd o:t O) ,of""""" ) I /o / or./tt N t+{ o ?s cn(.;,a' 'od I ctlt ! fi sH ie $s {8 II B5 lztolrlr I s ?0o\0 FOe: I <q 99 6!ga a> ta 63 ;6gq ;6 ?f <ts Ctl (n (r{o ll-onox -Jr a C) r-rrl ITrrt rrt --{ N(,.t I! Io,Fo x-3 0)- Ao aao a. 0) o @ t-Oc) --{oz. OTl rrlXTT-On -{on EOn z. c) T] (o * 5 ;t E d* $ * BORING 1 EL. 6,307' LEGEND TOPSOIL. SANDY CLAY, FIRM, MOIST, DARK BROWN, ORGANIC. 0 SAND AND CLAY (SC-CL); STIFF T0 VERY STIFF, SLIGHTLY MOIST, TAN TO BROWN, SLIGHTLY CALCAREOUS.14/12 WC=26.0 DD= 1 00 -200=44 GRAVEL, COBBLES AND BoULDERS (GM) SILTY, SANDY, VERY DENSE, SLIGHTLY MOIST, BROWN, BASALT FRAGMENTS. E 14/12 WC=20.4 DD= 1 04 DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE. Ftd trJtL I-F o_ trJo 10 7 /12 WC=15.1 DD= 1 06 -200=47 UC=1,300 ., i"^ DRIVE SAMPLE BL0W COUNT. INDICATES THAT 14 BLOWS 0Ft+/ tL A 14o-pouND HAMMER FALLTNG J0 tNcHES wERE REQUTRED TO DRIVE THE SAMPLER 12 INCHES. I enncrcnl AUGER REFUSAL. 15 13/12 WC=12.2 DD=118 -200=41 NOTES 1. THE EXPLORATORY BORING WAS DRILLED ON DECEMBER 29, 2023 WITH A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGER. 2 THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 20 5. THE ELEVATION OF THE EXPLORATORY BORING WAS OBTAINED BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN PROVIDED. 4, THE EXPLORATORY BORING LOCATION AND ELEVATION SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOG REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE TIME OF DRILLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSTTY (pcf) (lSrV O ZZ1O); +4 = PERCENTAGE RETAINED ON NO. 4 SIEVE (ISTU O OSIS); -2OO = PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D 1140); UC = UNCONFINED COMPRESSIVE STRENGTH (psi) (ASTM D 2166); 23-7 -640 Kumar & Associates LOG OF EXPLORATORY BORING Fi1. 2 f SAMPLE OF: Sondy Cloy FROM:Boringl@4' WC = 26.0 %, DD = 100 pcf, -200 = 44 % I I I i- I I : I i NO MOVEMENT UPON WETTING 'r Tharc t€st r6sults opply only to the somplca tdtod. The tcsiing t.port sholl nol bc reproduced, cxccpt in full, {ithout th€ wdtt€n opprovol of Kumor ond AssocioteB. lnc, S*cll Consolidotion tcatlnq p€rfomcd in dccddoncc witb Asllil D-4546. 1 \o JJ UJ =a 0 -1 -2z.otr o =o anz.o C) -5 -4 1 1,0 - KSF 10 100 Fig.3SWELL_CONSOLIDATION TEST RTSULTS23-7 -640 Kumar & Associates lcn Kumar & Associales, lnc.6 Geotechnical and Materials Engineers and Environmental Scientists TABLE 1 SUMMARY OF LABORATORY TEST RESULTS 1 9 4 2 I4 12.2 1 5 1 20.4 26.0 106 104 100 SAMPLE LOCATION BORING DEPTH GRADATIONNATURAL MOISTURE CONTENT NATURAL DRY DENSITY GRAVEL (%) SAND (%) 118 44 PERCENT PASSING NO. 200 stEVE 4 1 47 LIQUID LIMIT MI PLASTIC INDEX lolol ATTERBERG LIMITS 1,300 Very Clayey Sand Very Clayey Sand Sandy Clay Very Clayey Sand SOIL TYPE UNCONFINED COMPRESSIVE STRENGTH No.23-7-640