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Home My WebLink AboutSubsoils Report for Foundation Designrcrt Kumar & Associates, lnc.' Geotechnical and Materials Engineers and Environmental Scientists An Employes OvrnEd 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 l,ocations: Dorver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, and Summit County, Colorado Jvne26,2024 Anne and Laurence Sperry 33 Sunhill Lane Newton, Massachus etts 02459 anne@sperryinc.com Project No.24-7-269 Subject: Subsoil Study for Foundation Design, Proposed Residence and Barn, Lots2 and 3, Hunt Ranch, County Road 102, Garfield County, Colorado Anne and Laurence: 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 proposal for geotechnical engineering services to you dated April 8,2024. 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 single-story wood-framed home with an attached Earage located on the site as shown on Figure 1. Ground floors will be either slab- on-grade or stnrctural floor over a crawlspace in the residence and slab-on-grade in the gange. The nearby barn is assumed to be a one- or two-story wood or steel-framed structure with a slab- on-grade floor. Cut depths are expected to range between about 2 to 4 feet. Foundation loadings for this type of construction are assumed to be relatively light and typical of the proposed type of construction. Ifbuilding 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: At the time of our site exploration, the building area was vasantpasture. The site was situated near the top of a low rolling hill, with the ground surface sloping gently down to the southwest. Vegetation consisted of grass and weeds in building area with sage brush to north of building area. Subsurface Conditions: The subsurface conditions at the site were evaluated by excavating eight exploratory pits at the approximate locations shown on Figure 1. The logs of the pits are presented on Figure 2. In Pits 1-6, and Profile Pit 1, the subsoils encountered below about3/+ to lYzfeet of topsoil, consist of medium stiffto stiffslightly sandy to sandy silt and clay down to the explored depths of 5%to 7Yz feet. In Profile PiI2,the sandy silt and clay soils were underlain at a depth of 2% feet by basalt gravel and cobbles in a white silty, clayey matrix with some basalt -2- boulders that extended down to the maximum explored depth of 5 feet. Results of swell- consolidation testing performed on relatively undisturbed samples of the silt and clay soils, presented on Figure 3, indicate low compressibility under existing moisture conditions and light loading and a low to moderate collapse potential when wetted under a constant light surcharge. No free water was observed in the pits at the time of excavation and the soils were slightly moist. Foundation Recommendations: Considering the subsoil conditions encountered in the exploratory pits and the nature of the proposed construction, we recolnmend spread footings placed on the undisturbed soil bearing pressure of 1,500 for support of residence and barn. wetting some a minimum width of 18 for continuous walls and 2 feet soils tend to compress after settlement. Footings should be for columns. Loose disturbed soils 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 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 be designed to resist alateral earth pressure based on an equivalent fluid unit weight of at least 300 pcf for the on-site soil as backfill. Floor Slabs: The natural on-site soils, exclusive of topsoil, are suitable to support lightly to moderately 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 base course should be placed beneath slabs-on-grade for support. This material should consist of minus 2-inch aggregate with less than 50Yo passing the No. 4 sieve and less thanl2%o passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95%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. Underdrain System: A perimeter foundation drain around the proposed slab-on-grade or shallow crawlspace construction should not be required. If a perimeter drain is installed, 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 I foot below lowest adjacent finish grade and sloped at a minimum lo/oto a suitable gravity outlet. Free-draining granular material Kumar &Associates, lnc. o Project No. 24-7-269 -3- used in the underdrain system should contain less than 2% passing the No. 200 sieve, less than 50% passing the No. 4 sieve and have a manimum size of 2 inches. The drain gravel backfill should be at least lYzfeet deep. Surface Drainage: The following drainage precautions should be observed during construction and maintained at all times after the residence and bam have been completed: l) Inundation ofthe foundation excavations andunder-slab areas shouldbe avoided during conskuction. 2) Exterior backfrll should be adjusted to near optimum moisture and compacted to at least 95Yo of the ma><imum standard Proctor density in pavement and slab areas and to at least 90Yo of the maximum standard Proctor density in landscape areas. Free-draining wall backfill should be capped with about 2 feet of the on-site, finer graded soils to reduce surface water infiltration. 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 first 10 feet in unpaved areas and a minimum slope of 3 inches in the first l0 feet in pavement and walkway areas. A swale will be needed uphill to direct surface runoff around the residence and barn. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires regular heavy irrigation should be located at least 5 feet from the building. Consideration should be given to the use of xeriscape to limit potential wetting of soils below the foundation caused by irrigation. Limitations: This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this areaat this time. We make no waranty 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 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 concerned about MOBC, then a professional in this special field of practice should be consulted. Our findings include interpolation and exfapolation of the subsurface conditions identified at the exploratory pits and variatibns 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 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. 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 Kumar & Associates, lnc. @ Project No. 24-7-269 -4- monitor the implementation of our recommendations, and to verifu 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. If you have any questions or if we fnay be of further assistance, please let us know Respectfully Submitted, Kumar & Associates, lnc. David. A. Noteboom, Staff Engineer Reviewed by Daniel E. Hardin, DANikac attachments cc Figure I Pits Figure2 *Exploratory Pits Figure 3 - Legend ahd Notes Figures 4 thru 7 - Swell-Consolidation Test Results Table I - Summary of Laboratory Test Results Laurence Sperry 0Epqrrli@lsperr.yiqa,sqtt) Forum Phi - Ryan Lee@) ,/tl>\ e Kumar & Associates, lnc"ni Proiect No. 24-7-269 E ::j..'t::i:' PN /f'PP-1t'PIT 1 l,' PP-2 )l Pa:TSE3 Sl{OProCaTla\ Pil 2 PIT 5 PIT 5 PIT 4 .r:a c TO COUNTY ROAD 1 02 60 APPROXIMATE SCALE_FEET 24-7-269 Kumar & Associates LOCATION OF EXPLORATORY PITS Fig. 1 PIT 1 Et.7570' PIT 2 EL. 7568' PIT 5 EL. 7572' o 0 WC= 13.6 DD=94 WC= 1 2.9 DD=85 -200=50 FtJ L^JL I-F(L LJo 5 WC=9.6 DD=8 1 5 F!J trJt! I-F(L UJo 10 I WC= 1 0.3-l -zoo=as LL=24 Pl=8 10 PIT 4 EL.7574' PIT 5 EL. 7576' PIT 6 EL.7578' 0 0 FLItJt! I-F(L LTo WC= 1 0.0 DD=77 F LrJt!L IIF(L UJo 5 5 10 10 PP- 1 EL. 7564' PP_2 EL. 7551' 0 0 FtJ LJtL I-F(L LJo 5 5 F LrJ TJtL I-F(L tJlo 10 l0 -L '-lL 24-7 -269 Kumar & Associates LOGS OF TXPLORATORY PITS Fis. 2 E LEGEND TOPSOIL; ORGANIC SILT AND CLAY, ROOTS, STIFF, SLIGHTLY MOIST, MEDIUM BROWN CLAY AND SILT (CL-ML); SLIGHTLY SANDY TO SANDY, STIFF To MEDIUM STIFF, SLIGHTLY MOIST, MEDIUM TO LIGHT BROWN, TRACE TO SLIGHT CALCAREOUSNESS WITH DEPTH, SLIGHTLY CLAYEY SILT LOAM. GRAVEL (GM-cc); BASALT COBBLES, GRAVEL AND SMALL BOULDERS lN A WHITE SILTY CLAYEY MATRIX. F t HAND DRIVE SAMPLE DISTURBED BULK SAMPLE. NOTES 1. THE EXPLORATORY PITS WERE EXCAVATED WITH A CAT 306 MINI-EXCAVATOR ON MAY 29, 2024. 2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROM FEATURES SHOWN ON THE SITE PLAN PROVIDED. 5. THE ELEVATIONS OF THE EXPLORATORY PITS WERE OBTAINED BY INTERPOLATION BETWEEN CONTOURS ON THE SITE PLAN PROVIDED. 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 THE TRANSITIONS MAY BE GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF EXCAVATION. PITS WERE BACKFILLED SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSITY (PCt) (ISTU D 2216); _2OO= PERCENTAGE PASSING NO. 2OO SIEVE (ASTM D LL = LIQUID LIMIT (ASTM D a518); PI = PLASTICITY INDEX (ASTM D 4518). 1 1 4o); Kumar & Associates LEGEND AND NOTES Fig. 524-7 -269 € SAMPLE OF: Very Sondy Silt ond Cloy FROM:Pit1s-2' WC = 13.6 %, DD = 94 pcf tull, uithdt h. ritt n opp'!6l d Kumo. od kodotq lnc. Selll Cffillddil tdng pdffi6d in omdoncc dth m D-4il6. ln ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 2 )s JJtd =o I z9F o Jotnz.oo 0 -2 -4 -6 -8 1.0 APPLIED 24-7 -269 Kumar & Associates SWELL_CONSOLIDATION TEST RESULTS Fig. 4 E SAMPLE OF: Silty Cloyey Sond FROMIPit2('-3' WC = 12.9 %, DD = 85 pcf -2OO = 50 % Thr b ln 0-4il6.lirh i, ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 2 ;q JJ LJ =a 0 -2 -4z.otr o Joaz.o() -6 -8 -10 -12 1 24-7 -269 Kumar & Associates SWELL-CONSOLIDATION TESI RESULTS Fig. 5 E 2 0 -2 x JJ UJ =vl I z.otr o =oaz.o C) 4 -6 -8 1 0 1 2 -14 -16 -18 -20 1 t.0 APPLIED PRESSURE - KSF 10 SAMPLE OF: Very Sondy Silt ond Cloy FROMTPiI 5@4' WC = 9.6 ?6, DD = 81 pcf Snllod Cffillddlon rd(nS pdom.d L oEdof,d rfth ffi D-gA. ;iil ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 1i- 24-7 -269 Kumar & Associates SWELL_CONSOLIDATION TEST RESULTS Fig. 6 E I SAMPLE OF: Very Sondy Silt ond Cloy FROM:Pil 4@3.5' WC = 1O.O %, DD = 77 pcf l ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING tdd. ft! lnc. Srstl ln 1 0 ;q J J -lLJ =a t-2 zIF o_a Io UIz.oo_4 I I.O APPLIED PRESSURE - KSF 100 24-7-269 Kumar & Associates SWTLL-CONSOLIDATION TEST RESULTS Fig. 7 I (+A fi,'r;lfl'ffiffffi liv i' * " TABLE 1 SUMMARY OF LABORATORY TEST RESULTS No.2tl-7-269 SOIL TYPE Very Sandy Silt and Clay Silty Clayey Sand Silty Clayey Sand Very Sandy Silt and Clay Very Sandy Silt and Clay (osfl UNCONFIl{ED COMPRESSIVE STRENGTH 82443 8l 77 10.3 9.6 10.0 8 4 3y,4 3 50 13.6 t2.9 85 942 3 DEPTH 1 2 PIT ATTERBERG LIMITSGRADATION LIQUID LIMIT PERCENT PASStt{G NO. 200 stEvE NATURAL DRY DEilStW NATURAL MOISTURE CONTENT SAND (%) GRAVEL (%) PLASTIC INDEX