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HomeMy WebLinkAboutSoils Report 03.12.2019K' A d'irofirtiRniai 5020 C,ourWV Road 151 fax: (0/0) 945-0454 (-70171Cd 2:7L SUBSOIL STUDY FOR FOUNDATION DESIGN I? r4:.OPOSED RESIDENCE AMENDED TRACT 36, ANTLERS ORCHARD TBD LAFRENZ LANE EAST OF COUNTY ROAD 237 GARFIELD COUNTY, COLORADO PROJECT NO. 19-7-124 MARCH 12, 2019 PREPARED FOR: MARIA AND DANIEL BUCIO 1160 BALLARD AVENUE SILT, COLORADO 81652 uatkowqruct; /(.0. Wocrafe4 (30 / '49-2017/ TABLE OF CONTENTS PURPOSE AND SCOPE OF STUDY - I - PROPOSED CONSTRUCTION - 1 - SITE CONDITIONS - 1 - FIELD EXPLORATION - 2 - SUBSURFACE CONDITIONS - 2 - FOUNDATION BEARING CONDITIONS - 3 - DESIGN RECOMMENDATIONS • - 3 - FOUNDATIONS - 3 - SLABS -ON -GRADE - 4 - UNDERDRAIN SYSTEM • - 4 SURFACE DRAINAGE - 5 - LIMIT'AT'IONS - 5 FIGURE I - LOCATION OF EXPLORATORY BORINGS FIGURE 2 -. LOOS OF EXPLORATORY BORINGS FIGURE 3 - LEGEND AND NOTES FIGURES 4 and 5 - SWELL CONSOLIDATION TEST RESULTS TABLE 1- SUMMARY OF LABORATORY TEST RESULTS Kumar & Associates, inc. Project No. 'F.)- -124 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located north of Lafrenz Lane and east of County Road 237, (hwiield 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 Alberto Bucio dated January 29, 2019. A field exploration program consisting of exploratory borings was conducted to obtain information on the subsurface conditions. Samples ofthe 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 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 will be a single -story structure with a structural floor above crawlspace and located approximately as shown on Figure 1. Grading for the structure is assumed to be relatively minor with cut depths between about 2 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 building site consisted of an irrigated grass field at the thne of our study. The ground surface slopes down to the southwest at a grade of around 8%. Juniper trees cover the ground outside of the grass field. About 4 inches of snow covered the building site at the time of our field exploration. Frojnct Nn. 194424 -2 - FIELD EXPLORATION The field exploration for the project was conducted on February 5, 2019. Two exploratory borings were drilled at the locations shown on Figure 1 to evaluate the subsurface conditions. The borings were advanced with 4 -inch diameter continuous flight augers powered by a truck- mounted CMC; -45B drill rig. The borings were logged by a representative of Kumar & Associates. Samples of the subsoils were taken with 1% inch and 2 -inch 1.1.). spoon samplers. The samplers were 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 returned 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 were somewhat variable and below about 1/2 foot of topsoil consist of roughly stratified sand and clay with scattered gravel underlain at depths of about 101 and 121 feet by silty clayey sand and gravel to the boring depths of 21 and 26 feet, Laboratory testing performed on samples obtained from the borings included natural moisture content and density and 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 compressibility under natural low moisture and light loading and variable compressibility or expansion when wetted. The upper soils showed low compressibility or expansion whereas the sample from 10 feet, Figure 4, showed moderate expansion potential when wetted. The laboratory testing is summarized in Table 1. No free water was encountered in the borings at the time of drilling and the subsoils were slightly moist. e.;to'lcz,t_A3 o .F„'x .24 Kumar a ate :, Inc, -3 - FOUNDATION BEARING CONDITIONS The upper soils encountered at the site to roughly 5 to 10 feet depth generally show low compressibility or expansion potential and are typically expected to be encountered at shallow excavation depths. The deeper moderately expansive soil appears to be an anomaly, but the exp nsion.potesttial of the soils should be further evaluated at the time of excavation. The underlying sand.and .gravel soilsencountered below 10' and 12'/% feet should provide good support of foundations with low compressibility potential. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory borings and the nature of the proposed construction, we recommend tile building he founded with spread footings bearing (3i1 the upper natural soils. with a risk °t':tiovemcni mainly if the hearing soils are wetted. The design and c()nstru(: tion criteria presented below should be observed year a spread footing foundation system. 1) Fiiuliiigs placed on the undisturbed natural soils should he designed for an allowable bearing pr ,sure of 1,500 psi*. Based on experience.. we expect initial settlement of footings designed and constructed as discussed in this section will be about 1 inch or 1(. Additional differential settlement/heave up to around 1 inch could occur if the bearing soils are wetted. 2) Tlie t otings should have a minimum width of 16 inches for cpntinunus walls and 2 feet for isolated pads. 3) Exterior tbotings and footings beneath unheated areas should be provided with adequate soil cover above their tearing 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 length of at least 14 feet. Foundation walls acting as retaining structures should also be designed to resist lateral earth pressures corresponding to an equivalent fluid unit weight of at least 50 pcf. -4- S) The topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the 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. SLABS -ON -GRADE The natural on-site soils, exclusive of topsoil, can be used to support lightly loaded slab -on -grade construction with a risk of settlement/heave if the bearing soils are wetted. To reduce the effects of some differential movement, slabs should be separated from all bearing walls and columns with expansion joints which allow unrestrained vertical movement. Floor slab control joints should he 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 50% retained on the No. 4 sieve and less than 12% passing the No. 200 sieve. All till materials for support of floor slabs should be compacted to at least 95% of maximum standard Proctor density at a moisture content near olt'tinnurn. Required till c:an consist of the on- site soils devoid of vegetation. topsoil and oversized incl[. [1NDFRDRAIN SYS'T'EM it is our understanding line 1?tclposed finished floor elevation at the lowest level is at or above the surrounding grade. Therefore, a tiaundalion drain system is. not needed at this site: with proper site grading. It has been our experience in the area that local p relied groundwater can develop during times orlic:avy pre •ilaittation or stational rtrnolf. t"rw en giound during spring runoff can create a perched condition. We rccomnncnd below -grade construction, such as retaining walls and basement areas, be protected from wetting and hydrostatic pressure buildup by an underdrain and wall drain syAcni. If the design chantey to include a basement, we should he contacted for additiowil rcconnsn endations. -5 - SURFACE DRAINAGE Proper surface grading and drainage will be critical to preventing wetting of the bearing soils and potential distress to the building. The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: 1) 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% of the maximum standard Proctor density in pavement and slab areas and to at least 90'/0 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 irrigation 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 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 PrcIed•N. iYf3..;-1 4 -6 - during construction appear different from those described in than report, we should be notified so that re-evaluation oldie 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 ,continueF:i consultation and field services during construction to review and monitor the implementation sof your TOOMITYlaidati011S, and to verify that the recommendation ss 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, • -) a Steven L. Pawlak, P . € . n 15222 fir Reviewed by: t r;;., 1 lrP�se_ iin^R ■a'c,ue anv r, .tF' _ Daniel E. Hardin, i'.1:. SLP/kac c No. t X424 Tract 2a not. acres p + 49+41x1 Rfid L . ! ,.I /' 6'GI r�cn(ir�y and Ulaih' varw.wnc .. • _ as it aFfrvis i eFa 29 tom_ yYN� • LASE y- tYs'�' + ��r `�•A :- —."�f REM J/ � 1_�' MYapedray and Utle*Y Earsn.n+ �/ ett Kt/MARK; PROPERTY CORNER PIN ELEV. =100' ASSUMED. r// Foos,/ Raba" Y/Alps. / r CCv FLS 13551r [. Ips nl r' SeRSCY7iY .. _�- ......-•'- - A67 Jt .vt+Tw.Ynf dn. 5 Pew V11+4as. Iff Erµ PLR I& 8rGlj Cirdc U i/.r• 4 bei7aticn WpvlM onint Amora�d Tract 2 319.689 eq.R 7.318 Done ntyr 1/4 Fvovr rcllrn @S reueW MY /An. Cay .Wwora Ilvsunit E PROPOSED RESIDENCE BORING 1 BP BORING 2 •Amended TrQ' t -31341 g 292.803 9q..ft. rr / 8.717 acnes: / A g fJ.�r � g rl, ,�i 6 = 59.44.44'% r » i LID 53.94'is+v- T__,__.... 11. 6i461557 4. . 90.41"' /e ' �r+i.1w�•""-•-•r•- /My Il••••-•". rJ' �• �1��A � �SS� -_�. } I /, TO CR 237 56,31•" Am ld ,1 -woo* 37 I+I w orwr L ' 34 rests softchard aro.: x F,"zeoi 7.4131 ease �nrr_ .- rap±.': r.8�•;:.n•-r ;er4{':s Yu •: ry11pi6 t." topar-$ w37'37 G} f TrD 14 Iwo I�4Y pP 79 IIP.1 100 0 107 700 APPROXIMATE SCALE—FEET K104M1yy Ltrita aF '1 .rmy tkan 09 990t0C aA$ 909S - 19-7-124 Kumar & Associates LOCATION OF EXPLORATORY BORINGS Fig. 1 Wt W W W W; a W. 0• 0 5 10 15 20 25 30 BORING 1 EL. 92' 16/12 WC=4.3 00=108 39/12 WC=5.8 DD=115 —200=57 52/12 WC=6.5 DD=130 35/12 42/12 25/12 BORING 2 EL. 96.5' 19/12 WC=5.5 D1)=105 19/12 37/12. WC =5.9 DD=124 —200=51 65/12 17/12 0 5 10 15 20 I 25 30 of as 19-7-124 I Kumar & Associates LOGS OF EXPLORATORY BORINGS Fig. 2 LEGEND TOPSOIL; ORGANIC SANDY SILT AND CLAY, FIRM, MOIST, DARK BROWN. I:: SAND AhILI CLAY (SC -GL); SILTY. SCAT I ERED GRAVEL, MEDIUM DENSE/VERY STIFF, SLIGHTLY r • rf luiuiS i , LIGHT BROWN.. CALCAREOUS TRACES. SAND AND GRAVEL (SM --GM); SILTY, CLAYEY, POSSIBLE COBBLES, MEDIUM DENSE TO DENSE. SLIGHTLY MOIST, MIXED BROWN. i DRIVE SAMPLE, 2 -INCH I.D. CALIFORNIA LINER SAMPLE. DRIVE SAMPLE, 1 3/8 -INCH I.D. SPLIT SPOON STANDARD PENETRATION TEST. 16/12 DRIVE SAMPLE BLOW COUNT. INDICATES THAT 16 BLOWS OE A 140• -POUND L-1AMMEI FALLING 30 INCHES WERF REQUIRED TO DRIVE THE SAMPLER 12 MCI II. S. NOTES 1. THE EXPLORATORY BORINGS WERE DRILLED ON FEBRUARY 5, 2019 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. 3. THE ELEVATIONS OF THE EXPLORATORY BORINGS WERE MEASURED BY HAND LEVEL AND REFER TO THE BENCHMARK ON FIG. 1. 4. THE EXPLORATORY BORING LOCATIONS AND ELEVATIONS SHOULD BE CONSIDERED ACCURATE ONI.Y TO 1HE 13EGra:r•. IMPLIED DY THE METHOD 1JSLD. 5. THE: LINES 6E1 WEEN MATERIALS SHOWN ON THE EXPLORATORY BORING LOGS REPRESENT THE APPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TRANSITIONS MAY Rf GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE BORINGS AT THE TIME OF DRILLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTENT (%) (ASTM D 2216); DD = DRY DENSITY (pcf) (ASTM D 2216); -200= PERCENTAGE PASSING NO. 200 SIEVE (ASTM D 1140). Kumar 8, Associates LEGEND AND NOTES .3 —3 —4 4 3 z 0 0 n Z 0 —1 3 —2 Pr,41 Ur•ORd Th WIlnq 1;7 .1, nal 1. reppbx.tuceml. • •• , cra Oomolotret., $.010 T1 1.0 APPLIED PRESSURE K5F 10 100 •. _ .•-•••••••.•-•••••• - - • - -- 11 19-7-124 1 Kumar & Associates SWELL -CONSOLIDATION TEST RESULTS FROM: El...14-inc! I •63= 1.9 APPLIED PRESSURE — CS 10 r• 10E1 pct 1,\ • o; ....1 ' SAMPLE OF: Sandy Clay FROM: Boring t 0 10' WC 6.5 %. DO = 130 pcf 106 1 CONSOLIDATION - -3 -4 -5 -6 • in.n sruwM n.vcayV -vnm G. zt °1s0, .11tin 46"4 xrnw ans f. Id IL e B.r1 ac .R! D-lS/l. i • SAMPLE OF: Clayey Sand FROM: Boring 2 0 2.5' WC = 5.5 %, DE = 105 pcf 1.A APPLIED PRESSURE — KSF 10 ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING 106 1 19-7-124 Kumar & Associates SWELL -CONSOLIDATION TEST RESULTS Fig. 5 Geotechnical and Materials Engineers and Environmental Scientists kumarusa.com TABLE 1 SUMMARY OF LABORATORY TEST RESULTS Project No. 19-7424 SAMPLE LOCATION _ NATURAL NATURAL MOISTURE DRY BORING DEPTH CONTENT DENSITY iR) tpcis GRADATION ATTpRBiwRG LIMITS GRAVEL SAND PERCENT NO. LIQUID LIMIT PLASTIC PASSING (%) 1 (°fie) 200 SIEVE INDEX 1 2% 4.3 108 5 5.8 115 10 is 6.5 130 2 2' 5.5 105 k 57 1%) UNCONFINED COMPRESSIVE STRENGTH {psi SOIL TYPE Very Clayey Sand Very Sandy Clay Sandy Clay 10 5.9 124 t 51 Clayey Sand Very Sandy Clay }