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Home My WebLink AboutSubsoils Report for Foundation DesignlGrtiffilfl*ìi'fËtrf 'YÊü**' An Employcc Ownsd Compony 5020 County Road 154 Glenwood Springs, CO 81601 phone: (970) 945-7988 fax: (970) 945-8454 email : kaglenwood@kumarusa.com wu,r'.kumaLus¿t.colll Ofüce Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED AUXILARY DWELLING UNIT LOT 1, RUIZ SOUTH MINOR SUBDTVTSTON COUNTY ROAD 346 GARFIELD COUNTY, COLORADO PROJECT NO. 22-7-3 49.01 FEBRUARY 24,2023 PREPARED FOR: ESAU RUIZ 6799 COANTY ROAD 346 SILT, COLORADO 81652 esauruiz90@gmail.com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITIONS FIELD EXPLORATION.... SUBSURFACE CONDITIONS FOUNDAITON BEARING CONDITIONS DESIGN RECOMMENDATIONS ...... FOI.INDATIONS FLOOR SLABS UNDERDRAIN SYSTEM LIMITATIONS...... FIGURE I - LOCATION OF EXPLORATORY BORING FIGURE 2 - LOG OF EXPLORATORY BORING FIGURE 4 - SWELL-CONSOLIDATION TEST RESULTS TABLE 1 - SUMMARY OF LABORATORY TEST RESULTS 1 I I I ...........-2 - a -3- -3- -3- 4- -4- -5- Kumar & Associates, lnc. o Project No. 22-7 -349.01 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed auxiliary dwelling unit (ADU) residence to be located on Lot 1, Ruiz Minor Subdivision, County Road 346, south of Silt, Garfield 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 as supplemental services to our agreement for geotechnical engineering services to Esau Ruiz dated May 9, 2022. We previously performed a subsoil study for the main residence at the lot and submitted our flrndings in a report dated June 20,2022, Project No.22-7-349. 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 analyzed to develop recommendations for foundation types, depths and allowable pressures t'or the proposed building foundation. 'l his 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 ADU residence will be a single story structure located on the lot as shown on Figure 1. Ground floors will be structural over crawlspace, possibly with a slab-on-grade attached garage. Grading for the structure is expected to be relatively minor with cut depths between about 2Y, to 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 lot was vacant pasture land at the time of our field exploration and the ground surface covered with about 3 inches of snow. The terrain is relatively flat with a gentle slope down to the north at a grade of less than 5 percent.egetation consists of grass and weeds FIELD EXPLORATION The field exploration for the project was conducted on January 5,2023 . One exploratory boring was drilled at the location shown on Figure I to evaluate the subsurface conditions. The boring Kumar & Associates, lnc. @ Project No. 22-7 -349.0'l 1 location was as directed by the client. The boring was advanced with 4-inch diameter continuous flight augers powered by a truck-mounted CME-458 drill rig. The boring was logged by a representative of Kumar & Associates. 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-I586. The penetration resistance values are aî 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 are shown on Figure 2. The subsoils encountered, below about Yzfoot of topsoil, consisted of stiff to medium stiff, sandy to very sandy silt and clay. The sandy to very sandy silt5, ¿¡¿ cla¡, i¡.1u6ed some silt5, cl¿ttt tund layers or zones and extended down to the boring depth of 21 feet. Laboratory testing performed on samples obtained from the borings included natural moisture content and density, and percent finer than sand size gradation analyses. Results of swell- consolidation testing performed on relatively undisturbed drive samples of the soils, presented on Figure 4, indicate moderate compressibility under conditions of loading and wetting with a low hydro-compression potential. The laboratory testing is summarized in Table 1. No groundwater was encountered in boring at the time of drilling and the subsoils were slightly moist to very moist with depth. FOUNDATION BEARING CONDITIONS The upper sandy silt and clay soil encountered in the boring possess low bearing capacity and moderate settlement potential. Based on our experience in the area, there are dense coarse granular soils with depth at the site that possess moderate bearing capacity and relatively low settlement potential. The proposed residence can be founded with spread footings bearing on the natural fine-grained soils with a risk of settlement. A lower risk option would be to extend the bearing level down to the underlying coarse granular soils with a relatively deep foundation system such as helical piers or micropiles. Provided below are recommendations for a spread footing foundation. If recommendations for a deep foundation system are desired, we should be contacted to provide them. Kumar & Associates, lnc. @ Project No. 22-7 -349.01 -J- DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we believe the building can be founded with spread footings bearing on the natural soils with a risk of foundation movement. 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 "999!-pased on experience, we expect settlement of footings designed and constructed as discussed in this section will be on the order of I to 2 inches. 2) The footings should have a minimum width of l8 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. æ' 4) Continuous foundation walls should be well 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 lateral earth pressure corresponding to an equivalent fluid unit weight of at least 50 pcf. 5) All topsoil and any loose disturbed soils should be removed and the footing bearing level extended down to the relatively firm natural soils. The exposed soils in footing area should then be moistened and compacted. 6) A representative of the 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 differentialmovement, 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 sand and gravel road base should be placed beneath at grade slabs for support and to facilitate drainage. Kumar & Associates, lnc. @ Project No. 22-7 -349.01 4 This material should consist of minus Z-inch aggregate with at least 50% retained on the No. 4 sieve and less than 12%o passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least95Yo of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the on-site soils devoid of topsoil and oversized (plus 6-inch) rocks. UNDERDRATN SYSTEM It is our understanding the proposed finished floor elevation at the lowest level is at or above the surrounding grade. Therefore, a perimeter foundation drain system should not be needed. It has been our experience in the area that localperched groundwater can develop during times ofheavy precipitation or seasonal runoff. Frozen ground during spring runoffcan also create a perched condition. We recommend below-grade construction, such as retaining walls and crawlspace areas greater than 4 feet deep, 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 Providing and maintaining proper surface drainage will be critical to the long-term satisfactory performance of the proposed residence and to prevent wetting of shallow crawlspace areas. The following drainage precautions should be observed during construction and maintained at all times after the ADU residence has been completed: l) 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 90%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 frrst l0 feet in unpaved areas and a minimum slope of 3 inches in the first l0 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 infiltration. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. Kumar & Associates, lnc. @ Project No. 22-7 -349.01 5 s)Landscaping which requires regular heavy irrigation, such as sod, and sprinkler heads 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 irrigation. 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 boring drilled at the location indicated on Figure 1, 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 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 evolves, we should provide continued consultation and field services during construction to review and monitor the implementation of our recommendations, and to verifz that the recommendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recomrnendations presented herein. We recomrnend on-site observation ofexcavations and foundation bearing strata and testing ofstructural filI by a representative of the geotechnical engineer. Respectfu lly Submitted, Kum¿rr & As David A. Young, DAYlkac Kumar & Associates, lnc.'i'Project Flo. 22"V -345.01 ? E I à I Prcposed Buildíng I I I -1 t29'.27',W 2635.24'Re.eption No 954652 Bedls soo'2527 8 I7.oo Countg Road No. 346 -s--/-:R PLS 36572"N __J__1 i 20 úÌit! tusëmút Creøledúith Rui¿ &uth Minor tubdidslo^ T I I 6. 0 u5 We st Øf,ñunicdtiot Bøok ago, Poge 143 I I \ t\ BORING 5 I I I I I It37.4' I l I I I I PROPOSED MAIN RESIDENCE O||et I I BORING 2 I 3ú5.2' LOT 1 I BORING I I I I I LOT 2 I I I30,O Udlit! tuseñe^t Crcotcd 1uíth Ruiz sdth Mao¡ turdi,bbn Re.¿ption No. - I I 276.8' I I I I I10.o -\ --- -ì --f 25.O I I I l*.u N A9"45'13',E 627.68' LEGEND: O AONIHO FOR CURRENT STUDY O eoRINO FoR PREVIoUS STUDY, PRoJECT NO, 22-7-349 50 0 0 APPROXIMATE SCALE_FEET 22-7 -349.01 Kumar & Associates LOCATION OF EXPLORATORY BORING Fig. 1 Ê BORING 5 LEGEND TOPSO|L; ORGANIC SANDY SILT AND CLAY,FROZEN, M0|ST, BROWN 0 12/ 12 WC=8.6 DD= 1 05 -200=78 SILT AND CLAY (ML-CL); SANDY T0 VERY SANDY T0 OCCASI0NALLY SILTY CLAYEY SAND, STIFF TO MEDIUM STIFF, SLIGHTTY MOIST TO VERY MOIST WITH DEPTH, BROWN. 5 11/12 WC=8.2 DD= 1 06 DRIVE SAMPLE; 2-INCH l.D. CALIFORNIA LINER SAMPLE. ."r,"DR|VE SAMPLE BLOW COUNT. INDICATES THAT 12 BL0WS 0FtLt tL A 140-p0uND HAMMTR FALLTNG J0 rNcHEs WERE REQUTRED TO DRIVE THE SAMPLER 12 INCHES. ---> DEPTH AT WHICH BORING CAVED IMMEDIATELY FOLLOWING DRILLING. 10 e /12 WC=6.6 -200=36 F t¡JtdL! I-t--(L LJo NOTES 15 8/ 1z Y'lC=22.0 DD= 1 00 -200=92 1 THE EXPLORATORY BORING WAS DRILLED ON JANUARY 5, 2022 WITH A 4-INCH DIAMETER CONTINUOUS FLIGHT POWER AUGTR. 2. THE LOCATION OF THE EXPLORATORY BORING WAS MEASURTD APPROXIMAÏELY BY PACING FROM FEATURES SHOWN ON ÏHE SITE PLAN PROVIDED, 20 7/12 3. THE ELEVATION OF THE EXPLORATORY BORING WAS NOT MEASURED AND THE LOG OF THE EXPLORAÏORY BORING IS PLOTTED TO DEPTH. 4. THE EXPLORATORY BORING LOCATION SHOULD BE CONSIDERED ACCURATE ONLY TO THE DEGREE IMPLIED BY THE METHOD USED. 25 5. THE LINES BETWEEN MATERIATS SHOWN ON ÏHE EXPLORATORY BORING LOG REPRESENÏ THE APPROXIMATE BOUNDARIES BEÏWEEN MATERIAL TYPES AND THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE TIME OF DRILLING, 7. LÀBORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DTNSITY (PCf) (ASTM D 2216); -200 = PERCTNTAGE PASSING N0. 200 SIEVE (ASTM D 1 1 4o). LOG OF EXPLORATORY BORING Fi1. 222-7 -349.01 Kumar & Associates SAMPLE OF: Sondy Silt ond Cloy FROM:BoringS@5' WC = 8.2 %, DD = 106 pcf innot bê ¡cproduc.d, ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING il .:.i il il ir I 1,0 APPLIED 1 1 à( JJ l¡J =tn I z.otr ô =o tJ1zo C) 0 -1 -2 -3 SWELL_CONSOLIDATION TEST RESULTS Fig. 322-7 -349.01 Kumar & Associates I(+'T Kumar & Associales, Inc,' Geotechnical and Materials Engineers and Environmental Scientists TABLE 1 SUMMARY OF LABORATORY TEST RESULTS No. 22-7-349.01 SOIL TYPE Sandy Silt and Clay Sandy Silt and Clay Silty Clayey Sand Sandy Silt and Clay (psf) UNCONFINED COMPRESSIVE STRENGTH I%l PLASTIC INDEX ATTERBERG LIMITS LIQUID LIMIT Iolol PERCENT PASSING NO. 200 stEVE 78 36 92 SAND (%) GRADATION (%) GRAVEL 100 NATURAL DRY DENSI'fY (ocfl 10s8.6 1068.2 6.6 22.0 ("/"1 NATURAL MOISTURE CONTENT SAMPLE LOCATION J al/L/2 t5 5 l0 DEPTHBORING