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HomeMy WebLinkAboutSubsoil Studyt crt iiffilffiï:#n1,,rËü** An Employcc olrncd Compony 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970)945-7988 fax: (970) 945-8454 email : kaglenwood@kumarusa.com www.kumarusa.com Office Locations: Denver (HQ), Par{<er, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado SUBSOIL STT]DY FOR F'OT]NDATION DESIGN PROPOSED RESIDENCE LOT 5, BLOCK 8, BATTLEMENT CREEK VTLLAGE 168 MEADOW CREEK DRIVE GARFIELD COUNTY, COLORADO PROJECT NO.20-7-61s TEBRUARY 16,2021 PREPARED F'OR: STE\rE PLAYTON C/O RUSSELL CARTWRIGHT 35 WILLO\ryVItr\il WAY PARACUTE, COLORADO 81635 russecart@,qmail.com PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 5o Block 8, Battlement Creek Village, 168 Meadow Creek Drive, Garfìeld County, Colorado. The project site is shown on Figure l. 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 Steve Playton c/o Russell Cartwright dated January 5,2021. An exploratory boring was drilled to obøin 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 recommendatíons for foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obt¿ined 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 single-story wood frame structure with an attached gamge. Ground floors will be structural over crawlspace for the living areas and slab-on-grade for the garage. Grading for the structure is expected to be relatively minor with cut depths between about 2 to 5 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 lot was vacant at the time of our field exploration and the ground surface appeared mostly natural. The tenain is moderately sloping down to the west. Elevation difference across the lot is about l0 ar l}feet. Vegetation consists of grass, weeds and sagebrush. There are scattered Kumar & Associates, lnc. @ Project No. 20-7-613 aJ DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we believe the building can be founded with lightly loaded spread footings bearing on the natural soils with some risk of settlement. The risk of settlement is primarily if the bearing soils were to become wetted and precautions should be taken to prevent wetting. A lower risk of settlement would be to extend the foundation bearing down to the relatively incompressible coarse granular soils. The design and construction criteria presented below should be observed for a spread footing foundation system. l) Footings placed on the undistwbed natural soils can 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. Additional settlement could occur if the bearing soils become wetted. The magnitude of the additional settlement would depend on the depth and extent of the wetting but may be on the order of I to l% inches. 2) The footings should have a minimum width of l8 inches for continuous walls and 2feet 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 heavily reinforced top and bottom to span local anomalies such as by assuming an unsupported lengfh of at least 14 feet. Foundation walls acting as retaining structures should also be designed to resist lateral earth pressures as discussed in the "Foundation and Retaining Walls" section of this report. 5) All topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the fïrm natural soils. The exposed soils in footing area should then be moistened and compacted. Kumar & Associates, lnc. o Project No.20-7613 5 strength. Suiøble factors of safety should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides of the footings to resist lateral loads can consist of the on-site soils and should be compacted to at least 95Vo of the maximum standard Proctor density at a moisture content near optimum. FLOOR SLABS The natural on-site soils, exclusive of topsoilo are suitable to support lightly loaded slab-on-grade construction. There could be some slab settlement if the subgrade were to become wetted. 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 base course should be placed immediately slabs to facilitate drainage. This material should consist of minus 2-inch aggregate with at least 50% retained on the No. 4 sieve and less than ZYopassingthe No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least95To of maximum standard Proctor density at a moisture content near optimum. Required fïll can consist of the on- site soils devoid of topsoil and oversized rocks. LTNDERDRAIN SYSTEM Although groundwater was not encountered during our exploration, it has been our experience in the area that local perched groundwater can develop dwing times of heavy precipitation or seasonal runoff. Frozen ground during spring runoffcan also create a perched condition. We recoûìmend below-grade construction, such as retaining walls and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain system. A perimeter foundation drain around shallow crawlspace areas (less than 4 feet deep) may not be needed with adequate compaction of foundation backfill and positive surface drainage. If a foundation drain is used, the drains should consist of 4 inch diameter PVC drainpipe placed in the bottom of the wall backfill sunounded above the invert level with free-draining granular Kumar & Associates, lnc. 6 Project No. 20-7-613 -7 - 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 extrapolation of the subsurface conditions identified at the exploratory boring 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 evolveso we should provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to verifr that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recommend on-site observation of exôavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, Kumar & Associates, lnc. James lI. Parsons, E.I Reviewed by: David A. Young, P JHP/kac cc: All Draft Í Kumar & Associates, lnc. ô Project No. 20-7"613 BORING 1 LEGEND -0 17 /12 WC=3.7 DD=l 1 1 -200=81 N n ffi TOPS0IL¡ SANDY SILT IYITH SCATTERED C0BBLES AND BoULDERS, FtRlt, Uo|ST, BRoWN. SILT (ML); C|AYEY, SANDY, VERY STIFF, TAN, SLIGHTLY MOIST -Ê, 17/12 lïC=5.5 0D=1 01 GRAVEL SANDY, (cc-cv); ryrTH BASALT coBBrrs AND BoutJERs, CI.AYEY, SILTY, DENSE, MOIST, MIXED BROWN AND GRAY. 27 /12 F I DRTVE SAMPLE, 2-|NCH l.D. CALIF0RN|A LTNER SAMPLE. t- l¡J l¡Jl! IEFo-l¡lê 1 0 27/12 WC=,{.0 DD=1 07 DR|VE SAMPLE, I 5/S-|NCH r.D. SPUT SP00N STANDARD PENETRATION TEST. ¡7¡eDRlYE SAMPLE BLOW COUNT. INDICATES THAT ,17 BL0WS 0F",,-A I4O-POUND HAIIMER FAIUNG 30 INCHTS WERE REQUIRED TO DRIVE THT SAMPLER 12 INCHES. - 15 50/4 NOTES 1. THE EXPLORATORY BORING WAS DRILLTD ON JANUARY 11,2021 IYITH A 4.INCH DIAMËTER CONTINUOUS FTIGHT POWER AUGER. -20 50/3 2. THE LOCATION OF THE EXPLORATORY BORING WAS MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITT PITN PROVIDED. 3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT MEASURED AND TI{E LOO OF TI{E EXPTORATORY BORINC IS PLOTTED TO DEPTH. -25 1, TI{E EXPLORATORY BORING LOCATION SHOULD BE CONSIDERED ACCURATT ONLY TO THI DEGREE IMPLIED BY THE METHOD USED. 5. THE UNIS BETTTEEN MATERIAIS SHOWN ON THE EXPLORATORY BORING LOG REPRESENT TI{E APPROXIilATE BOUNDARIIS BETWEIN MATERIAL TYPES AND THE TRANSITIONS MAY BE CRADUAt. 6. GROUNDWATER WAS NOT TNCOUNTERED IN THE BORING AT THE TIMI OF DRILLING. 7. LABORATORY TEST RESULTS: WC = IYATER CONTENT (X) (ASTM D 2216)¡ DD = DRY DENSITY (pcf) (ASTM D 2216)¡ -200 = PEROENTAGT PASSING N0. 200 SIEVE (ASTM D lt10), Kumar & Associates LOG OF EXPLORAÏORY BORING Fig. 220-7-613 lGrtU*l**ç[i*å-*TABLE 1SUMMARY OF LABORATORY TEST RESULTSIBORII¡GI041(ftìDEPÏH4.AJ.J3.7t%ìNATURATTqSTURECOI{TEt'lTt07I01II1(%)GRA\ÆL(%)SAl,lDI{ATURAtDRYDENSITY81PERCEIÍTPASSING NO.2msEvEATIERSfÁìLIQIJIDLITIT{%lPLASÏC[{DÐ(RG LITITSSandy Clayey SiltSandy Clayey SiltSandy Clayey SiltSOLTYPEU}¡CONFI¡IEDcotPREsstvESTRENGfiNo.20-7