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Home My WebLink AboutSubsoil Studytcrt*itilfi.trfffffi 'r"Êü*,,, An Employcc Owncd Compony 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email: kaglenwood@Jcumarusa.com www.kumarusa. com Ofüce Locations: Dørver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado RECEIVET} GARFIELD COUNTY COMMUNITY DEVELOPMENT SUBSOIL STUDY FOR FOUNDATION DESTGN PROPOSED RESIDENCE LOT 48, SPRTNG RrDGE RESERVE 24IIIDDEN VALLEY DRTVE GARFIELD COUNTY, COLORADO PROJECT NO. 21.7-2I-O APRrL 16,2021 PREPARED FOR: JASON SCHMIDT 2960 SKY RANCII DRIVE GLENWOOD SPRINGS, COLORADO 81601 k2.iason@,vahoo.com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITIONS FIELD E)GLORATION SUBSURFACE CONDITIONS DES IGN REC OMMENDATION S FOUNDATIONS FLOOR SLABS LINDERDRAIN SYSTEM ........ SURFACE DRAINAGE LIMITATIONS FIGIJRE 1 - LOCATION OF E)GLORATORY BORINGS FIGURE 2 - LOGS OF E)GLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURES 4 E¿ 5. SWELL-CONSOLIDATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS I I I -1- a -3 - -4- 5 Kumar & Associates, lnc. ô Project No.21-7-210 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on the west side of Lot 48, Spring Ridge Reserve, 24 Hidden Valley Drive, Garfield County, 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 agreement for geotechnical engineering services to Jason Schmidt dated February 16,202I. A field exploration program consisting of exploratory borings was conducted to obtain information on the 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 analyzed to 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 residence will be a 3,600 square foot, one-story wood frame structure over a crawlspace. The detached garage will have a slab-on-grade floor. Grading for the structure is assumed to be relatively minor with cut depths between about 2lo 4 feet. We assume relatively light foundation loadings, typical of the proposed type of construction. 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 site was vacant and the house corners were staked at the time of our field work. The lot is relatively flat with a slight slope down to the northwest. Vegetation consists of grass and weeds Nearby lots are developed with one to two-story wood frame houses. FIELD EXPLORATION The field exploration for the project was conducted on March 25,202T. Two exploratory borings were drilled at the locations shown on Figure 1 to evaluate the subsurface conditions Kumar & Associates, Inc. o Project No.21-7-210 The borings were advanced with 4 inch diameter continuous flight augers powered by truck- mounted CME-458 drill rig. The borings were logged by a representative of Kumar & Associates, Inc. Samples of the subsoils were taken 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 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, below 71/zfeet of topsoil, consist of about l6Yzfeet of medium stiffto very stiff, silty sandy clay overlying 13 to 23 feet of medium dense, silty clayey sand down to the maximum depth explored in Boring 2 of 4I feet. Medium dense, silty sandy gravel soils were encountered in Boring 1 below 31 feet. Laboratory testing performed on samples obtained from the borings included natural moisture content, density and percent frner than sand size gradation analyses. Results of swell- consolidation testing performed on relatively undisturbed drive samples of the silty sandy clay soils, presented on Figures 4 and 5, generally indicate low to moderate compressibility under conditions of loading and wetting. The shallow clay sample from Boring I showed a low expansion potential when wetted under a constant light load. The laboratory testing is summarized in Table 1. No free water was encountered 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 exploratory borings and the nature of the proposed construction, we recommend the buildings be founded with spread footings bearing on the natural soils below the topsoil. Kumar &Associates, lnc. o Project No. 21-7-210 -J- 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. 2) The footings should have a minimum width of 18 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 area. 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 50 pcf for the onsite soils as backfill. 5) All existing topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the relatively stiffnatural subsoils. The exposed soils in footing area should then be moistened and compacted. 6) A representative ofthe geotechnical engineer should observe all 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. A minimum 4 inch layer of free- draining gravel should be placed beneath the garage slab to provide a break for capillary moisture size. This material should consist of minus 1-inch aggregatewith at least 50% retained on the No. 4 sieve and less than 2o/o passing the No. 200 sieve. All fìll materials for support of floor slabs should be compacted to at least 95o/o of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on- site soils devoid of vegetation and topsoil. Kumar & Associates, lnc. 0 Project No. 21-7-210 -4- UNDERDRAIN SYSTEM An underdrain system should not be needed for shallow crawlspace (less than 4 feet) and slab- on-grade areas provided that positive surface drainage away from the house and detached garage is maintained. We recommend deeper crawlspace and basement areas be protected from wetting and hydrostatic pressure buildup by an underdrain system. If needed, the drains should consist of drainpipe placed in the bottom of the wall backfill surrounded above the invert level with free-draining granular material. The drain should be placed at each level ofexcavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimvm lYa to a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than ZYo 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 lVz feet deep. STIRFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: 1) Inundation ofthe 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 90o/o of the maximum standard Proctor density in landscape areas. 3) The ground surface surounding 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 paved areas. Free-draining wall backfill (if any) should be covered with filter fabric and capped with about 2 feet of the on-site soils to reduce surface water infìltration. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy inigation should be located at least 5 feet from foundation walls. Consideration should be given to use of xeriscape to reduce the potential for wetting of soils below the building caused by inigation. Kumar &Associates, lnc. o Project No.21-7-210 -5- LIMITATIONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this arca at this time. We make no warranty either express or implied. The conclusions and recommeirdations submitted in this report are based upon the data obtained from the exploratory borings drilled at the locations indicated on Figure 1, the proposed type of construction and our experie,nce 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 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 constuction to review and monitor the implementation of ourrecoÍrmendations, and to verifu that the recommendations have bee,n appropriately interpreted. Significant design changes may require additional analysis ormodifications to the recommendations presented herein. Vy'e recommend on-site observation of excavations and foundation bearing shata and testing of structural fill by a representative of the geotechnical engineer. Respectñrlly Submitted, Kumar & Daniel E. Reviewed by: Steven L. Pawlak, P.E DEHlkac Kumar & Associates, lnc. 'l Project No. 21-7-?10 € ñ; t 60 APPROXIMATE SCALE_FEET LOCATION OF TXPLORATORY BOR¡NGS Fig.121 -7 -210 Kumar & Associates e ¡ I Ë {t I BORING 1 EL.=6433.5' BORING 2 BORTNG 6132.0' 0 0 11 /12 WC=15.6 DD=1 1 2 -2OA=82 23/12 5 38/12 WC=9.0 DD=1 1 I e/12 WC=12.8 DD=1 1 0 -2OO=73 12/12 WC=1 1.6 DD=1 1 5 10/12 WC=11.0 DD=1 07 -200=85 11/12 WC=14.9 DD=116 5 10 1013/12 WC=15.5 DD=118 -2OA=67 15 15 15/12 20/12 WC=14.0 DD=1 1 6 -2OO=74 20 20 t-bJl¡l LL I-F-o- LJ(f 12/12 1o/12 l- t¡J l¿ltL I :EFo- L¡Jô 25 25 11/12 15/12 50 50 55 5525/12 40 4020/12 45 45 Fig. 221-7-210 Kumar & Associates LOGS OF EXPLORATORY BORINGS E 3 ,;j I N LEGEND TOPSOIL¡ ORGANIC SANDY SILTY CLAY, FIRM, MOIST, DARK BROWN CLAY (CL): SILTY, SANDY, MEDIUM STIFF TO VERY STIFF, SLIGHTLY MOIST To MolST, RED, SLIGHTLY CALCAREOUS. SAND (SM*SG): S|LTY, C|áYEY, MEDIUM DENSE, MOIST, RED. W GRAVEL (GM): SANDY, SILTY, SCATTERED COBBLES, MEDIUM DENSE, SLIGHTLY MOIST, RED. DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE. ..'.ı DRIVE SAMPLE BLOW COUNT. INDICATES THAT ll BLOWS OF A 140-POUND HAMMERt tr tz FALuNG so TNcHES wERE REQU|RED To DRtvE THE SAMPLER 12 tNcHEs. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON MARCH 25, 2021 WITH A 4-INCH DIAMETER CONTINUOUS-FLIGHT POWER AUGER. 2. THE LOCATIONS OF THE EXPLORATORY BORINGS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE OBTAINED BY INTERPOLATION BEÏWEEN CONTOURS ON THE SITE PL"AN PROVIDED. 4. THE EXPLORATORY BORING LOCATIONS AND ELEVATIONS 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 WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D2216): DD = DRY DENSITY (pcf) (ASTM D2216)t -2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM 01140); 21-7-210 Kumar & Associates LEGEND AND NOTES Fig. 5 SAMPLE OF: Sondy Silly Cloy FROM:Boringl@4' WC = 9.0 ?6, DD = 1 18 pcf i 1 EXPANSION UNDER CONSTANT PRESSURE UPON WETTING I .0 APPLIED PRESSURE - KSF I APPLIED PRESSURE - KSF N JJ l¡J =ln I z.o 1- o =o U'z.o(J I 0 1 -2 -5 -4 3 2 N JJ l¡J =UI I z.o F- o Jo.Azo(J I 0 1 -2 -5 5 2 SAMPLE 0F: Sondy Silty Cloy FROM:Borlngl@10' WC = 11.6 76, DD = 113 pcf rlth tùt d. ñ¡ll, fllthout ffd ^.Þdstt not b. I : I i ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 21 -7 -210 Kumar & Associates SWELL_CONSOLIDATION TTST RESULTS Fig. 4 s I SAMPLE OF: Sondy Silty Cloy FROM: Boring2e^7.5' WC = 14.9 %, DD = 116 pcf I I i ì EXPANSION UNDER CONSTANT PRESSURE UPON WETTING .¡... l ; I mt b.rfthdi o¡d PRESSURE - KSF 10 100 3 2 1 N JJ UJ =n I zo F f¡ Joaz.o() -1 2 5 4 21-7-210 Kumar & Associates SWILL-CONSOLIDATION TEST RESULTS Fig. 5 ? I !s I lGrtiffiiffifffi1iiÍå**TABLE 1SUMMARY OF LABORATORY TEST RESULTSSOIL TYPESandy Silty ClaySandy Silty ClaySandy Silty ClaySandy Silty ClaySandy Silty ClaySandy Silty ClaySandy Silty ClaySandy Silty Clay{osf,UNCO.¡FINEDcoilPRESSt\ÆSÏRENGTH{%ìPLASTICINDÐ(ATTERBERG LI]IITSt%lLIQUID LITIITPERCENTPASSING NO.2æSIEVE8273856774(%)SAÀIDGRADATION(%)GRAVELtt2118110113t07116ll8ll6NATURALDRYDENSITY{ocfì1l.611.014.913.514,0{%tNATURATuosruRECONTENT15.69.0t2.8471057Yz0151tfrìDEPTTIISAIIPLE LOCATIONBORINGI2No. 21-7-210