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Home My WebLink AboutSubsoil Study for Foundation Design 10.13.2023lGn $;ffifi*11l:ffifr$v;*" An Employcc Owncd 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), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Surnmit County, Colorado . SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE LOT 1, MINEOTA RIDGE ESTATES, FILING 3 MINEOTA DRIVE, SOUTH OF SILT GARFIELD COUNTY, COLORADO PROJECT NO. 23-7-378 ocToBER 13,2023 PREPARED FOR: PEDRO PALMA CHAVEZ 6968 HTGHWAY 82, TRATLER 15 GLENWOOD SPRTNGS, COLORADO 81601 pedropalmaconstruction@gmail.com TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY... PROPOSED CONSTRUCTION . SITE CONDITIONS. FIELD EXPLORATION SUBSURFACE CONDITIONS FOUNDATION BEARING CONDITIONS ... DESIGN RECOMMENDATIONS ........... FOI.JNDATIONS NON-STRUCTURAL FLOOR SLABS TJNDERDRAIN SYSTEM SURFACE DRAINAGE............... LIMITATIONS 1 1-L- a ..-4- FrcuRE 1 - LOCATTON OF EXPLORATORY BORTNGS (EXTSTTNG CONDTTTONS) FrcuRE 1A - LOCATTON OF EXPLORATORY BORTNGS (PROPOSED CONSTRUCTTON) FIGURE 2 - LOGS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURES 4 and 5 - SWELL-CONSOLIDATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS I 1 1 1 Kumar & Associates, lnc, @ Project No. 23-7-378 1 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 1, Mineota Ridge Estates, Filing 3, Mineota Drive, south of Silt, 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 Pedro Palma Chavez dated June 20, 2023. 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 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 residence is assumed to be a2-story wood frame structure with an attached garage Ground floor could be slab on grade or structural over crawlspace. Grading for the structure is assumed to be relatively minor with cut depths between about 2 to 3 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 notif,red to re-evaluate the recommendations contained in this report. SITE CONDITIONS The site was vacant at the time of our field exploration and the ground surface appears to be natural and undisturbed. The terrain is relatively flat and gently sloping down to the north at a grade of approximately 5Yo. On-site vegetation consists of weeds. Nearby buildings consist of I and 2-story residences. FIELD EXPLORATION The field exploration for the project was conducted on August 29,2023. Two exploratory borings were drilled at the locations shown on Figure I to evaluate the subsurface conditions. The borings were advanced with 4-inch diameter continuous flight augers powered by a truck- mounted CME-458 drill rig. The borings were logged by a representative of Kumar & Associates, Inc. Kumar & Associates, lnc. @ Project No. 23-7.378 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 retumed 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 consist of about I foot of topsoil overlying very stiff to hard, silty, sandy to very clayey with gravel that extends down to the maximum depth drilled of 30 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, presented on Figures 4 and 5, indicate low to moderate compressibility under conditions of loading and wetting. The samples showed minor collapse or expansion potential when wetted under a constant 1,000 psf surcharge. The laboratory testing is summarizedinTable 1. No free water was encountered in the borings atthe time of drilling and the subsoils were slightly moist. FOUNDATION BEARING CONDITIONS The subsoils encountered in the borings at shallow depth are typically low strength clays with variable low to moderate compressibility. Shallow spread footings or structural slab with tumed down edges placed on the natural soils should be suitable for the building support with a risk of differential movement, mainly when the bearing soils are wetted. A heavily reinforced structural slab will help to mitigate the effects of differential movements and limit building distress. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we recommend the building be founded with spread footings or structural slab bearing on the natural soils. The design and construction criteria presented below should be observed for a spread footing foundation system. l) Footings placed on the undisturbed natural soils should be designed for an al1owablebearingpreSSureoJ@sedonexperience'weexpectinitial settlement of footings designed and constructed as discussed in this section will Kumar & Associates, lnc, o Project No. 23-7-378 -J- 2) be about I inch or less. There could be around I inch of additional settlement if the bearing soils are wetted, depending on the depth and extent of subsurface wetting. Structural slabs can be designed for a subgrade modulus of 100 pcf. The footings should have a minimum width of 20 inches for continuous walls and 2 feet for isolated pads. 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. Structural slab rftiiiaTffiperimeter turn down edge at least 18 inches 3) deep and be frost protected with minimum 2-inch-thick rigid foam insulation extending out at least 2 feet from the foundation edge. 4)Continuous foundation walls should be heavily reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 14 feet. Foundation walls acting as retaining structures (if any) should also be designed to resist alateral earth pressure coffesponding to an equivalent fluid unit weight of at least 55 pcf for the onsite soils as backfill. The topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the firm soils. The exposed soils in footing areas or below structural slab areas should then be moistened and compacted. Structural fill placed below foundation areas should be compacted to at least 98o/o of standard Proctor density atnear optimum moisture content. A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. s) 6) NON-STRUCTURAL FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to support lightly loaded slab-on-grade construction with a risk of settlement if the bearing soils are wetted. To reduce the effects of some differential movement, non-structural 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 such as road base should be placed beneath slabs for support. This material should consist of minus 2-inch aggregate with at least 50o/o retained on the No. 4 sieve and less than l2oh passing the No. 200 sieve. All fill 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. o Project No, 23-7-378 -4- I.'NDERDRAIN SYSTEM It is our understanding that the proposed finished floor elevation at the lowest level is at or above the surrounding grade. Therefore, a foundation drain system is not required. It has been our experience in the area and where there are clay soils 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 basement areas, 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 Proper surface grading and drainage will be critical to limiting subsurface wetting and potential building movements. The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: l) 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 95%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 surrounding the exterior of the building should be sloped to drain away from the foundation in all directions. We recommend a minimum slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of 3 inches in the first 10 feet in paved areas. 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 10 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 borings drilled at the locations indicated on Figure 1, the proposed type of construction and our experience in the area. Our services do not include determining the Kumar & Associates, lnc. @ Project No. 23-7-378 -5- 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 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 construction to review and monitor the implementation of our recommendations, and to veriff 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 excavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, Kumar & Associates, lnc. --l'/'/An,iv,J\ /,- P\ "/, */L--2**** Paul J. Graf, Staff Engineer Reviewed by Robert L. Duran, P.E. PJG&ac ccl. B atiz S oto (.{q, b eatriz soto @ grnai I . corn) Larry Sather (lar$rsa0rcr@rua[,qqu) tolltllJl Eit3p2 Kumar & Associates, lnc.,!Project No. 23"7-378 0 APPROXI MATESCALE-FEET 23-7 -378 Kumar & Associates LOCATION OF EXPLORATORY BORINGS EXISTING CONDITIONS Fig.1 F Ld trJ l,! I LJJ O U)t!F XovIL rL o o(o h ts ri P I FIz s g I d B {.fr- $is;EJ tpa F6 'b RtE ,/ s (9z E,oo 8I F N (9z Eo6 ,9t6€11 3.00&.G s D E .G&r t-H +rps+ Sene&BHyS) t ra \q 't 9\ t :sb s s It I oa.# og tt#b*,ocE- dq E @r\ FO Ir\ ImN oo (U'6 ooo 06 L (E E JY aoz E.oz.mo -=G? 9 -'x l-r #'q "6d c-> ><tJO LrJ ILAoo o_zO 3r Oo_l c; L! I - 9ZOZ BORING 1 EL. s,623' BORING 2 EL. 5,621' n 0 21/12 31 /12 q 44/12 WC=7.8 DD=121 -200=59 47 /12 WC=6.6 DD=1 1 6 -2OO=67 q 10 36/12 WC=6.3 DD= 1 06 22/ 12 WC=6.3 DD=99 10 F UJ LrJtL I-F o_ UJo 15 37/12 WC=4.9 DD=1 12 -200=58 1e/12 WC=6.7 DD= 1 00 -200=65 15 F LrJ trlt! I-F(L trlo 20 44/12 44/12 20 25 25 30 62/12 30 23-7 -378 Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 2 J I 3 I I LEGEND NhvN TOPSOIL; ORGANIC SILT AND CLAY, SANDY, SLIGHTLY GRAVELLY, FIRM, SLIGHTLY MOIST, BROWN. CLAY (CL); SILTY, SANDY TO VERY SANDY, SCATTERED GRAVEL, VERY STIFF, SLIGHTLY MOIST, BROWN. DRIVE SAMPLE, 2-INCH I.D. CALIFORNIA LINER SAMPLE 21/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 21 BLOWS OF A 14o_POUND HAMMER FALLING 50 INCHES WERE REQUIRED TO DRIVE THE SAMPLER 12 INCHES. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON AUGUST 29,2023 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. 5. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE OBTAINED BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN 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); -2O0 = PERCENTAGE PASSING NO. 200 SIEVE (ASTM 01140) 23-7 -378 Kumar & Associates LEGEND AND NOTES Fig. 3 .! I I I SAMPLE OF: Silty Sondy Cloy FROM:Boringl@9' WC = 6.3 %, DD = 106 pcf innot bo r6producod, without th€ writton opprovol of ond ksociotc, lnc. Sr6ll in EXPANSION UNDER CONSTANT PRESSURE UPON WETTING 1 JJ UJ =a I z.o F o =oazo C) 0 -1 -2 _z -4 E -6 1.0 APPLIED PRESSURE - KSF 10 100 2s-7 -378 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 4 = -9 ! I : I SAMPLE OF: Silly Sondy Cloy FROM:Boring2@9' WC = 6.5 %, DD = 99 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1 0 )q JJ LJ =tJ1 I zo F- o =oaz.oO -1 -2 -3 -4 -5 -6 -7 -9 1.0 APPLIED PRESSURE - KSF 10 100 23-7 -378 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig.5 rcn *rffih:',ffif$trnii:' i' *" TABLE 1 SUMMARY OF LABORATORY TEST RESULTS SOIL TYPE Silty Sandy Clay Silty Sandy Clay UNCONFINED COMPRESSIVE STRENGTH Silty Sandy Clay Silty Sandy Clay Silty Sandy Clay Silty Sandy Clay {%t PLASTIC INDEX 59 ATTERBERG LIMITS (%) LIQUID LIMIT 65 PERCENT PASSING NO. 200 stEvE s8 67 GRADATIONSAMPLE LOCATION DEPTHBORING NATURAL DRY DENSITY NATURAL MOISTURE CONTENT SAND (%) GRAVEL (f/"1 12I 106 rt2 116 99 100 7.8 6.3 4.9 6.6 6.3 6.7 4 9 T4 4 9 I4 1 2 No.23-7-378