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HomeMy WebLinkAboutSubsoils Report for Foundationt$tt$,äffi ,ffiifffiå,'IÊü** An Employcc Owncd Compony 5020 County Road I54 Glenwood Springs, CO 8ló01 phone: (970) 945-7988 fax: (970) 945-8454 enrai I : kaglenwood@kumarusa.com wwrv'.kumarusa.com Office Locations: Denver (l-lQ), Parkeq Colorado Springs, Fort Collins, Glenwood Springs, and Surnmit County, Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED IIESIDENCE LO't 2, BLOCK 6, STONE RIDG.E, BATTL$MENT MESA 91 LODGE POLE CIRCLE GARFIELD COUNTY, COLORADO PROJECT NO.21-7-895 FEBRUARY 8,2022 PREPARED FOR: RICK FARR 1310 WEST SPRUCE COURT RIFLE, COLORADO 81650 @ TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION SITE CONDITIONS..... SUBS URF'ACE CONDITIONS FOLINDATION BEARING CONDITIONS .. DESIGN RECOMMENDATIONS FOLINDATIONS FLOOR SLABS SURFACE DRAINAGE LIMITATIONS FIGURE 1 . LOCATION OF EXPLORATORY BORING FIGURI] 2 - LOG OF EXPLORATORY BORÍNG FIGURES 3 and 4 - SIVELL-CONSOLIDATION TEST RESULTS TABLE 1 . SUMMARY OF LABORATORY TEST RESULTS 1 -1- IìIELD EXPLORATION .,,.,,,.,,,..- 2 - 2- 3- ., -J- ..-4- ,,-4. 5 Kumar & Associates, lnc. o Project No,21-7.895 PURPOSE AND SCOPE OF ST'UDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 2, Block 6, Stone Ridge, Battlement Mesa, 91 Lodge Pole Circle, Garfield County, Colorado. The projcct sitc is shown on Figure l. Thc pllrposc ol'the study was to devclop recommcndatiorrs fbr the foundation design. The study was conclucted in accordancc with our agrecment fbr geotcchnical engineering services to Rick Farr, dated Novcmber 30,2021 . A field exploration program consisting of an exploratory boring was conducted to obtain information on the geneml subsurface conditions. Samples of the subsoils obtained during the field exploration were tested in the laboratory to determine their olassification, compressibility or swell and other engineering characteristics. The results of the field exploration and laboratory testing were analyzed to develop recommendations fbr foundation types, depths and allowable pressures for the proposed building foundation. This report summarizes the data obtained during this study and presents our conclusionso design recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The residence will be a single story wood frame structure over a crawlspace with an attached slab-on-grade garage located in the middle portion of the lot. Grading for the structures is expected to be relatively minor with cut depths between about 3 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 repoft. SITE CONDITIONS The lot was vacant and covered with about 1 I'oot of snow at the tirne ol'our field exploration. The teruain is relatively flat and gently sloping down to the northwest. The slope bccomes steeper down at the rear (north side) of the lot. Vegetation consists of sparse grass attd wccds. The adjacent lots to the east and west are both occupied with single family residences. Kumar & Associates, lnc. @ Project No.21-7-895 1 FIELD EXPLORATION The field exploration for the project was conducted on December 22,2021. One exploratory boring was drilled at the location shown on Figure I to evaluate the subsurface conditions. The boring was advanced with 4-inch diameter continuous flight augers powered by a truck-mounted CME-458 drill rig, The boling was logged by a representative of Kumar & Associates. Samples of'the subsoils were taken with I 3/s inch and 2-inch I.I). spoon samplers. The sarnplers were driven into the subsoils at various depths with blows fiom a 140 pound hammer falling 30 inches. This test is similar to the standard penetration test described by ASTM Method D-l586, 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 Figure 2. Tbe samples were returned to our laboratory for review by the project engineer and testing. SUBSURT'ACE CONDITIONS A graphic log of the subsurfàce conditions encountered at the site is shown on Figure 2. The subsoils encountered, below about% foot of topsoil, consistcd of very stiff, sandy to very sandy silt and clay undcrlain at a dcpth of about I fbct by rclativcly densc, silty clayey sand rvith basalt gravel and cobbles that extended down to the depth drilled of 26 feet. Laboratory testing performed on samples obtained frorn the boring included natural rnoisture content and density, and percent finer than sand sized gradation analysis. Results of swell- consolidation testing performed on relatively undisturbed drive samples of the upper fine grained soils. presented on Figures 3 and 4, indicate low compressibility under existing conditions and light loading and a low to modemte collapse potential (settlement under constant load) when wetted under constant light surcharge. One of the samples (Boring I at7') showed the higher collapse potential and moderately high compressibility when loaded after wetting, and may have been partly disturbed due to the sampling process, The laboratory testing is summadzecl in Table l. No lrec watcr was cncrJuntered in the borirrgs at tlte tittre of drilling and the subsoils were slightly moist to moist. FOUNDATION BEARING CONDITIONS The sandy silt and clay soils encountered at the site possess low bearing capacity and, in general, a nloderate settlernent potential especially when wetted. The underlying granular soils possess Kumar & Associates, lnc, o Project No.21-7-gS5 J moderate bearing capacity and a relatively lorv settlement potential. At assumed excavation depths, the fine grained soils are expeoted to be exposed at subgrade. Lightly loaded spread footings bearing on these soils can be used fbr support of the proposed construction with a risk of foundation settlement and possible building distress, primarily if the bearing soils become wetted. A lower risk option would be removc and replace a depth (typically 3 fcct) of the natural soils below footing arcas and replace in a moistened and compacted condition. Extending the loundation bearirrg down to the less cornpressible granular soils, such as by piles or piers, would provide a relatively low risk of foundation settlement. Provided below are recommendations for spread footings bearing on the natural soils with some risk of settlement and distress. If recommendations for structural fill below the footings or for piles or piers are desired, we should be contacted. DESIGN RECOMMENDATIONS FOI.INDATIONS Considering the subsurface oonditions encoLlntered 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 some risk of settlement. Precautions should be taken to prevcnt lvctting of the bcaring soils. The design and construction criteria presented below should be observed for a spreacl looting foundation system. l) Footings placed on the undisturbed natural soils should be designed f<¡r an allowable bearing pressure ased on experience, we expect settlement of footings designed constructed as discussed in this section will be up to about I inch. There could be some additional settlement if the bearing soils were to become wetted. The rnagnitude of the additional settlement would depend on the clepth and extent of the wetting but may be on the order of % to I inch. 2) The fbotings shotrld have a minimum width of I fì inchcs for continuous rvalls and 2 feet for isolated pads. 3) Exterior footings and footings beneath unhcated arsas should be provided with adequate soil cover of foundations at atea. elevation for frost protection. Placement exterior grade is typically usetl in this 1,200 psf. Kumar & Associates, lnc. o bearing Project No. 21-7-895 -4- 4)Continuous foundation walls should be heavily reinforced top and bottom to span local anomalies and better withstand the effects of some differential settlement such as by assuming an unsupported length of at least 14 feet. Foundation walls acting as retaining structures should also be designed to resist a lateral earth pressure corresponding to an cquivalent fluid unit wcight of at least 50 pcf. Alltopsoil and any loose disturbed soils should be rcmoved and the subgrade moistened and compacted. Any structural lìll belolv lootings should be compacted to at least 98o/o standard Proctor density at a moisture content near optimum. A representative of the geotechnical engineer should observe all footing6) 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. There could be some slab settlement if the subgrade were to become wetted as discussed abovc under "F'oundation Bearing Conditions". To reducc the effccts of somc diffcrential rnovernent, floor slahs shoulcl be scparatcd from all bearing walls and columns with cxpansion joints which allow unrestraincd vertical movemcnt. Floor slab control joints should be used to reduce damage due to shrinkage cracking. The requirements for joint spacing and slab reinfiorcement should be established by the designer based on experience and the intended slab use. A minimum 4 inch layer of sand and gravel base course should be placed immediately beneath floor slabs for subgrade supporl. This material should consist of nrinus 2-inch aggregate with at least 50% retained on the No. 4 sieve and less than l2o/o passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a rnoisture content near optimum. Required fill can consist of the onsite soils or imported 3/q-inch base course. SURI.ACE DRAINAGE A pcrimetcr foundation drain around shallow (lcss than 4 fect cleep) crawlspace areas should not be needed with proper compaction of foundation backfìll and positive surface drainage away frorn foundation walls. The following drainage precautions should be observed during construction and maintained at all times after the buildings have been completed: s) Kumar & Associates, lnc. @ Project No. 21-7'895 -5- l)Inundation ofthe foundation excavations and underslab areas should be avoided during oonstruction. Exterior backfill should be adjusted to near optimun moisture and compacted to at least 95% of the maximum standard Proctor density in pavement and slab areas and to at lcast 90% of the maximum standard Proctor density in landscape areas. The ground surface surrounding the exterior of the building should be sloped to drain away from the l'oundation in all directions. We recommend a rninimum slope of 12 inches in the first l0 feet in unpaved areas and a minimum slope of 3 inches in the first l0 feet in paved areas. 2) 3) 4)Roof downspouts and drains should the limits of all backfill. s)which requires regular heavy irrigation should be located at least f 10 feet from foundation LIMITATIONS This study has been conducted in accordance with generally accepted geotcchnical engincering principles and practices in this area at this time . We makc no warranty cithcr express or implicd. Thc conclusions and rccommendations submitted in this repoft are bascd upon thc data obtained frorn the exploratory boring drilled at the location indicated on Figure l, 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 extrapolation of the subsurface conditions identified at the exploratory trorings and variations in the subsrlrface 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 recomrnendations may be tnade. This report has been prepared for the exclusive use by our client for design pulposes. We are not responsible l'or technical intcrpretations by others olour inf'ormation. As the project evolves, wc should provide continued consultation and field services during construction to review and monitor the implcmentation of our recommendations, and to verify 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 Kumar & Associates, lnc. @ Project No, 21-7-895 -6- of excavations and foundation bearing strata and testing of structural fïll by a representative of the geotechnical engineer. Respectfully Submitted, Kumar & Associates, Inc. lJ#- David A. Noteboom, StaffEngineer Reviewed by David A. Young, DAY/kac qo q-zL 16 Kumar & Associates, lnc. @ Projecl No. 21"7-895 ? a , ,".u't;,. .-.,, t,,, oBOñtNo r 91 LOIGE POLE CrR (ooqe po¿e h"\dt''Þt hå.- tffi å,tw cte d #'* *-M*-.Æ 1 APPROXIMATE SCALE-FEET 21 -7 -895 Kumar & Associates LOCATION OF EXPLORATORY BORING Fig. 1f; t j E? ¡t u BORING I LEGEND -0 28/12 WCs4.5 TOPSO|L; ORGANIC SANDY SILTY CLAY, FIRM, M0lSï, BRoWN, R00T ZoNE. tD=99 -200=89 -5 le/12 WC=4.5 DD=97 31 /12 WC=13.9 DD=84 -200=77 CLAY AND SILT (CL-ML); SANDY TO VERY SANDY, GRAVELTY lt/ITH DEPÏH, VTRY STIFF, SLIGHTLY }'IOISÏ TO MOIST, ÏAN ÏO DARK TAN, SLIOHÏLY POROSIÏY, CALCARTOUS. SAND (SM-SC); S|LTY, CLAYEY, W|TH SCAITERTD BASÂLT GRAVTL AND COBBLES, SILÏ AND CLAY LTNSES, MEDIUM DENST TO DENSE, SLIGHTLY MOIST, MIXED BROWN AND GRAY-BROWN. DRIVE SAMPLI, 2-INCH I.D. CALIFORNIA LINER SAMPLE. - 10 32/12 i DR|VE SAMPLE, 1 3/8-|NCH r.D. SPL|T SP00N SIANDARD PENETRATION TEST. t-l¡l l¡JlÀ I :Et-o-l¡l6 2¡7¡2DR|VE SAMPLE BL0W COUNI. INDICATES THAT 28 8L0WS 0F I4O-POUND HAMMER FALLING 30 INCHES WERT REQUIRED TO DRIVE THT SAMPLTR 12 INCHES. f 5 27 /12 33/12 NOTES 1. THE EXPLORATORY BORING WAS DRÍLLED ON DICTMBER 22, 2021 WITH A 4-INCH DIAMEÏER CONTINUOUS FTIGHT POWER AUGER. 2. THE LOCATION OF ÏHT EXPLORATORY BORING WAS MEASURED APPROXIMÂTELY BY PACING FROM FEAÏURES SHOWN ON THE SIE PI-AN PROVIDED. -25 4s/12 3. ÏHE ELEVATION OF ÏHE EXPLORATORY EORING WAS NOT MEASURED AND THT LOG OF THE IXPLORATORY BORING IS PLOTTED TO DEPTH. 4, THE EXPLORATORY BORING LOCATION SHOULD BE CONSIOERED ACCURAÏT ONLY TO THE DECREE Il'lPLITt) BY THT METHOD USTD. -30 5. THE LINES BEÏWETN MAÏTRIALS SHOWN ON THT EXPLORATORY BORING LOG REPRESENT THE APPROXIMATE BOUNDARITS BETWEEN MAÏERIAL TYPES AND THE ÏRANSIÏIONS MAY BT GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORING AT THE TIME OF DRILLINC. 7, I.ABORAÏORY ÏEST RESULTS: WC = WATER C0NTENT (%) (ASTM D 2216); DD = DRY DENSITY (pcr) (lsrM D 2216)l -200 = PERCENTAGE PASSIN0 N0. 200 sltvE (ASTM D 1140). 21 -7 -895 Kumar & Associates LOG OF EXPLORATORY BORING ris, 2 SAMPLE 0F: Sondy Sllt ond Cloy FROM:Boringl(!4' WC = 4.5 /", DD = 97 pcf ADDITIONAL COMPRESSION UNDER CONSTANÏ PRESSURE DUE TO WETTING 1 0 às j-1 l¿l =tt1 t_2 zotr o_1 o at', oo_4 -5 .f 1,0 APPLIED PRESSURE - KSF 10 r00 21 -7 -895 Kumar & Associates SWTLL-CONSOLIDAÏION TTST RESULTS Fig. 3ð È I I SAMPLE OF: Sondy Silt ond Cloy FROM¡Boringle-7' WC = 13.9 %, DD = 84 pcf -20O = 77 % ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 2 0 o\ J^_J -Z l¿J =u1 t-4 zoË Õf-ootnzo<)-6 -10 -12 -14 I.O APPLIED PRESSURE - KSF 10 21 -7 -895 Kumar & Associates SWELL-CONSOLIDATION TEST RESULTS Fig. 4 ç I ¿ Í lGrtmråmfm1Ï,'ï'-":=TABLE 1SUMMARY OF LABORATORY TEST RESULTSNo.21-7-895Sandy Silt and ClaySandy Silt and ClaySOILTYPESandy Silt and Clay{osflUI{CONFI}¡EDcoilPRESSwESÏRENGÏ}IflolPLASTICIilDEXATTERBERG LI}IfTSLtoulD Ltilfrl%tPERCET{TPASSING NO.200 slEvE8977l?'lSANDGRADATION(%)GRAVELNATURALDRYDEilSTYNATURALTTIOISTURECONTE}¡T9997844.54.513.9{fr1DEPTT{I47SATIPI.E LOCATIONBORIT{GI