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Home My WebLink AboutSubsoil Study for Foundation Design 05.20.19l$rt *i KunsrtÂMdos, lec. 5020 County Road 154 Gsoteçhnieal ¿nd Materials Engineers Glenwood Springs, CO 81601 and Env¡fonmBnlal sr;enlisls phone: (g70) 945-7gsg fax: (970) 945-8454 email : kaglenwood@kumarusa.com An Employo€ orrnecl compony wwwkumarusa.com Ofüce Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado May 20,2019 RECEIVED Alex Gomez ll52l East 118ú Avenue Henderson, Colorado 80640 Aj-ga!1gzÊe4clfçz(àn$¡1. ca¡! iul I 5 201s GARFIELD COUNTY COMMUNITY DEVELOPMENT Project No.19-7-282 Subject: Subsoil Study for Foundation Design, Proposed Residence, Lot E-16, Aspen Equestrian Estates, 33 Equestrian Way, Ga¡field County, Colorado Alex: 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 May 6,2019. The data obtained and our recommendations based on the proposed construction and subsurface conditions encountered are presented in this report. Proposed Construction: The proposed residence will be a two story structure with attached gal:agelocated on the site as shown on Figure l. Ground floor will be structural over crawlspace or slab-on-grade. Cut depths are expected to range between about 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 lot was vacant at the time of our site visit. The lot is flat, slopes slightly down to the south and is vegetated with grass and weeds. Eagle Valley Evaporite bedrock is exposed on the valley hillsides to the north and south' Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating four exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are -2- presented on Figure 2. The subsoils encountered, below about I to 2 feet of topsoil, consist of sandy, silty clay to between 2 and 6 feet. Relatively dense, silty sand and gravel was encountered below the clay to the maximum explored depths of between 5 and 7 feet. Pit 4 encountered alayer of silty, clayey, sand from 2 to 4 feet. Results of swell-consolidation testing performed on a relatively undisturbed sample of sandy, silty clay, presented on Figure 3, indicate low compressibility under existing moisture conditions and light loading and moderate compressibility when wetted and subjected to increased loading. Free water was observed in the pits betwccn 5 and 6 fcct at the time of excavation. The upper soils were moist to very rnoist. Foundation Recommendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, we recoÍtmend spread footings placed on the undisturbed natural soil below the topsoil designed for an allowable soil bearing pressure of 1,500 psf for support of the proposed residence. The soils tend to compress when loaded and wetted and there could be post-construction foundation settlement of around I inch. Footings should be a minimum width of 18 inches for continuous walls and 2 feet for columns. The topsoil and loose disturbed soil encountered at the foundation bearing level within the excavation should be removed and the footing bearing level extended down to the undisturbed natural soils. 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 also be designed to resist a lateral earth pressure based on an equivalent fluid unit weight of at least 55 pcf fcrr the on-site soil as backfìll excluding organics. tr'loor 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 interior slabs to facilitate drainage, This Kumar & Associates, lnc Project No. 19.7-282 -3- material should consist of minus 2 inch aggregate with less than 50a/o passing the No. 4 sieve and less than 2o/o passing the No. 200 sieve. All filImaterials for support of floor slabs should be compacted to at least95%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. We recommend vapor retarders conform to at least the minimum requirements of ASTM 81745 Class C material, Certain floor types are more sensitive to water vapor transmission than others. For floor slabs bearing on angular gravel or where flooring system sensitive to water vapor transmission are utilized, we recommend a vapor barrier be utilized conforming to the minimum requirements of ASTM 81745 Class A material. The vapor retarder should be installed in accordance with the manufacturers' recommendations and ASTM 81643. Underdrain System: Free water was encountered during our exploration, and it has been our experience in the area and where clay soils are present 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 and crawlspace areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. 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 of excavation and at least 1 foot below lowest adjacent finish grade and sloped at a minimum lo/oto a suitable gravity outlet. Free-draining granular material used in the underdrain system should contain less than 2o/o passingthe No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum sizeof 2 inches. Thedraingravelbackfill shouldbeatleast 7/zfeetdeep. Surface Drainage: The following drainage precautions should be observed cluring 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. Kumar & Associates, lnc.Project No. 19-7-282 2) 4 Exterior backfill should be adjusted to near optimum moisture and compacted to at least 95% 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. Free-draining wall backfill should be covered with filter fabric and capped with about 2 feet of the on-site, finer graded soils to reduce surface water infiltration. The ground surface surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. IVe recommend a minimum slope of 6 inohes in the first 10 feet in unpaved a¡eas and a minimum slope of 2% inches in the first 10 feet in pavement and walkway areas. Roof downspouts and drains should discharge well beyond the limits of all backfill. Landscaping which requires regular heavy irrigation should be located at least 5 feet from the building. 3) 4) s) 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 pits excavated at the locations indicated on Figure I and to the depths shown on Figure 2,the proposed tlpe 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 fìndings 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 fiom those doscribed in this report, we should bc notificd 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. Vy'e 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 recommendations, and to veri$ that the recommendations Kumar & Associates, lnc.Project No. 1S-7.282 -5- have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommend on-site observation ofexcavations and foundation bearing strata and testing ofstructural filI by a representative of the geotechnical engineer. If you have any questions or if we may be of fu*her assistance, please let us know. Respectfully Submitted, Kumar & Associates, Inc. ,r/Ø James H. Parsons, E.I. Reviewed by: Steven L. Pawlak, JHPlkac attachments Figure Figure cc Pits 2-Pits Figure 3 - Swell-Consolidation Test Results Table I - Summaryof Laboratory Test Results Red House Architecture - Bruce Barth (bn¡cc(r-¿rerJhtiusca'rciiitecfur'e.com) Jose Campuzano (aspenvalleycarpentry@email.com) Kumar & Associates, lnc,Project No. 19-7-282 1 0 15 30 ,\PPROXIMATE SCÁLE FIET 19-7 -282 Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1 € 2 I I PIT 1 EL. 100' PIT 2 00' Ptï 3 00 Plï 4 EL.EL.1 EL.100 0 0 FUtil t¡- I-t--(L lriô WC= I 9.3 DD=96 \NC=17.1 DD= 1 09 -200=54 UC= 1 ,400 WC=i 2.5 DD=97 -2QO=23 t-- L¡l L!l! I-¡-fLt¡lô 5 5 t0 LEGEND 10 TOPSOIL; CLAY, SLIGHTLY SANDY, SILTY, ORGANICS, VERY MOIST, BROWN CLAY (CL); SANDY, SILTY, VERY MOIST, SOFT TO MEDIUM STIFF, LOW PLASTICITY' BROWN' SAND (SC-SM); CLAYEY, SILTY. LooSE. VERY MOIST. BR0WN GRAVEL ANÐ SAND (CU-Su); SILTY, VERY MoIST To WET, GRAY AND BROWN. k I HAND DRIVEN 2-INCH DIAMETER LINER SAMPLE. I DISTURBED BULK SAMPLE. -:- DEPTH TO WATER LEVEL ENCOUNTERED AT THE TIME OF DIOGING NOTES I. THE EXPLORATORY PITS WERE EXCÂVATED WITH A BACKHOE ON MAY S,2019 2, THE LOCATIONS OF THE EXPLORÀTORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM FEÂTURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORÀTORY PITS WERE MEASUREÐ BY HAND LEVEL ANÐ REFER TO PIf I AS 1OO" ASSUMED. 4. THE EXPLORATORY PIT 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 PIT LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THË TRANSITIONS MAY BE GRAÐUAL. 6. GROUND WATER WAS ENCOUNTERED IN THE PITS AT THE TIME OF DIGGING AT ÏHE DEPTHS SHOWN ON THE LOG. PITS WERE BACKFILLED SUBSEQUENT TO SAMPLING. 7, LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM T 2216); DD = DRY DENSITY (PCf) (ASTM D 2216); -2AO= PERCENTAGE PASSING NO. 200 SIEVE UC = UNCONFINED COMPRESSIVE STRENGTH (ASTM D lrao); (psr) (asru D 21 66); LOGS OF EXPLORATORY PITS Fig. 219-7-282 Kumar & Associates SAMPLE OF: Sondy, Silty, Cloy FROM:Pit2@-2.5' WC = 19.5 %, DD -- 96 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING t 0 ^-l J t! =u] l-s zo l- !-+o t!1z.o{)-5 -6 -7 -8 -9 ',0 APPUED 19-7 -282 Kumar & Associates SWELL-CONSOLIDATION ÏEST RTSULTS Fig. 3 l(+rtl(umar & Assoclates, lnc,Geotechnical and Maierials Engineersand Environmental Scientistskumarusa.comTABLE 1SUMMARY OF LABORATORY TEST RESULTSNo. l9-7.282Sandy, Silty, ClaySILTYPEVery Sandy, Silty, ClaySilty, Clayey, Sand(oslìUNCOI,IFIIIEDCOMPRESSTVESTRENGTH1400(%lPLASTICINDÐ(ATTERBERG LIMITSlo/olLIQUID LIM]Í23PERCENÏPASSTI{G ¡r0.200 stEVE54SANDf/"1GRADAÏION(/"1GRAVEL9610997NATURALDRYDËNS]TY(pc0(o/"\TIATURALMOISTURËCOi¡TENT19.3I71t2.5tf$DEPTH2%J'rr/^34Ptf2