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Home My WebLink AboutSubsoils Study for Foundationl(lrt l(uml & Assoclates, lnc.@ Geotechniæl and Materials Engineers and Environmental Scientists An Emdoycc 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 (tIQ), Parker, Colorado Sp.ingr, Fo¡t Collins, Glenwood Springs, and Summit Comty, Colorado SUBSOIL STUDY FOR FOUNDATION DESIGN PROPOSED RESIDANCE 16 RIDGE VIEW PLACE LOT 16, BLOCK 7, WILLOW CREEK VILLAGE BATTLEMENT MESA, COLORADO PROJECT NO.22-7-669 DECEMBER 5,2022 PREPARED FOR: RUSSELL CART\ilRIGHT 542 MEADOW LANE PARACHUTE, COLORADO 81635 @ TABLE OT'CONTENTS PURPOSE AND SCOPE OF STUDY .........- 1 - PROPOSED CONSTRUCTION I SITE CONDITIONS.... ...- 1 - FIELD E)OLORATION I SUBSURFACE CONDITIONS -') - DESIGN RECOMMENDATIONS ..- 2 - FOUNDATIONS a FOUNDATION AND RETAINING WALLS ............... - 3 - FLOOR SLABS ........ - 4 - LINDERDRAIN SYSTEM ,..,,.,.,. 4 - SURFACE DRAINAGE 5- LIMITATIONS 5 FIGURE 1 - LOCATION OF ÐGLORATORYBORING FIGURE 2. LOG OF EXPLORATORY BORING FIGURE 3 - SWELL-CONSOLIDATION TEST RESULTS TABLE I. SUMMARY OF LABORATORY TEST RESULTS Kumar & Associatæ, lnc. ó Prolect No.22-7-669 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 16, Block 7, Willow Creek Village, 16 Ridge View Place, Battlement Mesa" 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 proposal for geotechnical engineering services to Russell Cartwright dated October 4,2022. A field exploration progftun consisting of an exploratory boring 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 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 recornmendations and other geotechnical engineering considerations based on the proposed construction and the subswface conditions encountered. PROPOSED CONSTRUCTION The proposed residence will be a single-story, wood frame structure with attached garage. Ground floors will be structural over crawlspace for the living areas and slab-on-grade for the gatage. Grading for the structure is assumed to be relatively minor with cut depths between about 3 to 5 feet. \Me 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 COI\DITIONS The subject site was vacant at the time of ow field exploration. The ground surface is gently sloping generally down to the west at a grade of less than 5 percent. Vegetation consists of grass and weeds. FIELD EXPLORATION The field exploration for the project was conducted on October 14, 2022. 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 tuck-mounted CME-458 drill rig. The boring was logged by a representative of Kumar & Associates, Inc. Kumar & Associates, lnc. o Project No. 22-7-669 Samples of the subsoils were taken with l% inch and 2-inch I.D. 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-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 tlre Log of Exploratory Boring, Figure 2. The samples were returned to ow laboratory for review by the project engineer and testing. SUBSURFACE COIIDITIONS A graphic 1og of the subsurface conditions encountered at the site is shown on Figure 2. The subsoils consist of about one foot of topsoil overlying medium dense, sandy silt, silty sand and sandy clay to a depth of about 19 feet and underlain by dense, siþ to clayey gravel with basalt rocks down to the ma:<imum explored depth of 26 feet. Drilling in the underlying coarse granular soils with auger equipment was difficult due to the cobbles and boulders. Laboratory testing performed on samples obtained from the boring included natural moisture content and density and fîner than sand grain size gradation analyses. Results of swell- consolidation testing performed on relatively undisturbed drive samples of the sandy silt soils, presented on Figure 3, indicate low to moderate compressibility under conditions of loading and when wetted. The laboratory testing is summarized in Table 1. No free water was encountered in the boring at the time of drilling and the subsolls were slightly moist. DESIGN R.ECOMMEIIDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory boring and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural soils. 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 of 1,500 psf. Based on experience, \üe expect initial settlement of footings designed and constructed as discussed in this section will be about I inch or less. Additional differential settlement up to around 1 inch could occur depending on the depth and extent of future wetting and precautions should be taken to keep the bearing soils dry. Kumar & Associateo, lnc. @ Projec{ No.22-7-669 -J- The footings should have a minimum width of 18 inches for continuous walls and 2 feetfor 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 firea. Continuous foundation walls should be heavily reinforced top and bottom to span local anomalies such as by assuming an unsupported length of at least 12 feeL Foundation walls acting as retaining structwes should also be designed to resist lateral earth pressures ¿¡s discussed in the "Foundation and Retaining Walls" section of this report. The topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the firrn natural soils. The exposed soils in footing area should then be moistened and compacted. A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions. FOLINDATION AND RETAINING WALLS Foundation walls and retaining structures which are laterally supported and can be expected to undergo only a slight amount of deflection should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 50 pcf for backfill consisting of the on-site soils. Cantilevered retaining structures which are separate from the residence and can be expected to deflect sufficientþ to mobilize the fulI active earth pressure eondition should be designed for a lateral earth pressure computed on the basis of an equivalent fluid unit weight of at least 40 pcf for backfïll consisting of the on-site soils. All foundation and retaining structures should be designed for appropriate hydrostatic and surcharge pressures such as adjacent footings, trafftc, construction materials and equipment. The pressures recommended above assume drained conditions behind the walls and a horizontal backfill surface. The buildup of water behind a wall or an upward sloping backfill surface will inuease the lateral pressure imposed on a foundation wall or retaining structue. An underdrain should be provided to prevent hydrostatic pressure buildup behind walls. Backfill should be placed in uniform lífts and compacted to at least 90% of the maximum standard Proctor density at a moistwe content near optimum. Backfill placed in pavement and walkway areas should be compacted to at least 95Yo of the maximum standard Proctor density. 2) 3) 4) 5) 6) Kumar & Associates, lnc. o Proiect No. 22-7-669 -4- Care should be taken not to overcompact the backfìll or use large equipment near the wall, since this could cause excessive lateral pressure on t}re wall. Some settlement of deep foundation wall backfill should be expected, even if the material is placed correctly, and could result in distress to facilities constructed on the backfill. The lateral resistance of foundation or retaining wall footings will be a combination of the sliding resistance of the footing on the foundation materials and passive earth presswe against the side of the footing. Resistance to sliding at the bottoms ofthe footings can be calculated based on a coefficient of friction of 0.35. Passive pressure of compacted backfill against the sides of the footings can be calculated using an equivalent fluid unit weight of 325 pcf. The coefficient of friction and passive pressure values recommended above assume ultimate soil strength. Suitable factors of safety should be included in the design to limit the strain which will occur at the ultimate strength, particularly in the case of passive resistance. Fill placed against the sides ofthe footings to resist lateral loads should be compacted to at least95Yo of the maximum standard Proctor density at a moisture content near optimum. FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suit¿ble to support lightly loaded slab-on-grade construction with a risk of settlement mainly if the bearing soils are wetted. 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 free-draining gravel should be placed beneath basement level slabs to facilitate drainage. This material should consist of minus 2-inch aggregate with at least 50% retained on the No. 4 sieve and less than 2% passing the No. 200 sieve. All fill materials for support of floor slabs should be compacted to at least95%o of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the onsite soils devoid of vegetation, topsoil and oversized rock. UNDERDRAIN SYSTEM The proposed slab-on-grade garage and crawlspace should not require an underdrain system provided that good surface grading and drainage, as described below, is maintained around the exterior of the residence. 'We recommend crawlspace areas, deeper than about 4 feet, be protected from wetting and hydrostatic pressure buildup by an underdrain system. Kumar & Associates, lnc. o Project No. 22-7-669 -5- If 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 l%oto a suitable gravity outlet or sump and pump. Free-draining granular material used in the underdrain system should contain less than 2o/opassingthe No. 200 sieve, less than 50% passing the No. 4 sieve and have a maximum size of 2 inches. The drain gravel backfill should be at least lL/zfeetdeep. An impervious mernbrane such as 20 mil PVC should be placed beneath the drain gravel in a trough shape and attached to the foundation wall with mastic to prevent wetting of the bearing soils. SURFACE DRAINAGE Proper surface grading and drainage will be critical to keeping the bearing soils dry and limiting future settlement and building distress. The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: l) Inundation ofthe foundationexcavations and underslab areas shouldbe 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% of the maximum standar{ Proctor density in landscape areas. 3) The ground surface surrounding the exterior of the building should be sloped to drain away from the fotmdation in all directions. 'We recommend a minimum slope of 12 inches in the first 10 feet in unpaved areas and a minimum slope of 2Vzinchesin the first 10 feet in paved areas. Free-draining wall backfïll, if any, should be covered with filter fabric and capped with about 2 feet of the on-site, finer graded, soils to reduce surface water infiltration. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) 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 inigation. LIMITATIONS This study has been conducted in accordance with generally accepted geotechnical engineering principles and practices in this areaatthis time. V/e make no warranty either express or implied, Kumar & Associates, lnc. o Project No. 22-7-669 -6- The conclusions and rec¡mmendations 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 detertnining 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 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 therecommendations may be made. This report has bee,lr 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 ourrecommendations, and to veriff that the recofiunendations have been appropriately interpreted. Significant design changes may require additional analysis or modifications to the recommendations presented herein. We recomme,nd on-site observation of excavations and foundation bearing strata and testing of structural fill by a representativc of the geotechnical engineer. Respectfirlly Submiued, Kumar & Steven L. P SLPlkac Kumar & Associates, lnc. o Project No.22-7-669 R v c \)'?î <f \ -l 105flû S r i2 921 5 ô * F 39 .9S g ".4. R ."-* ,rre, ?.. ê ( .o 4 c(, 14 ù 10469 S F c'tf! dI € s a(s þù' \s \ ¡ 15634 S F Q't.ù ,/P/ '.> i- ,t't i APPROXIMATE SCALE_FEET 16 1? ,l/ + ra622o BORtt{G t $Ë' \ \ t¡J ¡oro ,åÍ) II 7. l\ t5 t3565 S F 22-7-669 Kumar & Associates LOCATION OF EXPLORATORY BORING 1Fig. c ü BORING 1 LEGEND o 5 32/12 21/12 WC=4.5 DD=100 -200=E9 21/12 t8/12 WC=4.8 DD=94 3E/12 WC=8.6 DD='101 -200=65 so/12 3s/12 n TOPS0IL: SAND AND SILT WITH R00TS AND 0RGANICS, FIRM' SL|GHTLY M0lSï, BRoWN. SAND AND S|LT (SM-ML) MEDTUM DENSE, SLIGHTLY lJolST, TAN. SUGHTLY CALCAREOUS. sANo AND CLAY (SC-CL), SILTY, DENSE/HARo, SUGHTTY ITOIST, LIGHT BROWN. GRAVEL (crr-cc) SANDY, STLTY, CLAYEY WTH DEPTH, BASALT GRAVEL, COBBI"ES ÀNO BOULDTRS, VTRY DENSE, SLIGHTLY MOIST, ì¡IXED BROIVN AND GRAY. F ¡ 32/12 F.LI t¡J l! I-Fo- l¡Jô f0 15 20 25 30 DRIVI SAMPLE, 2.INCH I.D. CALIFORNIA UNER SAMPLE. DRTVE SAilPH, t 3rl8-INCH l.D. SPUT SP00N STANDARD PENËTRATION TEST. DRIVT SAHPLE BLOW COUNT. INDICATES THAT J2 BLOWS OT A |,[0-P0UND llAlrlltR FAtllNC 30 INCHES WERE REQUIRED TO ÐRIVE THE SAITPTER 12 INCHES. NOTES I. THE IXPLORATORY BORING WAS DRITLID ON OCTOBER 14, 2022 WTH A ¿I-INCH DIAHETER C0NTINUOUS Fl.lGHT POWER AUGER. 2. THE LOCATION OF THE EXPLORATORY BORING WAS }¡EASURED APPROXIMATTLY BY PACING FRO}T FEATURES SHOWN ON THE SITE PI.AN PROVIDED. 5. THI TLEVATION OF THE EXPLORATORY SORING IVAS NOÏ MEASURED AND IHE LOG OF THE EXPLORATORY BORING IS PLONED TO DEPTH. 1. THE TXPLORATORY BORING LOCATION SHOULD BE CONSIDERED ACCURATT ONLY TO THE DEGREE IMPUED BY THE I'ETHOD USED. 5. THE LINES BETWEEN I'ATERIAIS SHOWN ON THE EXPLORATORY BORING LOG REPRISENT THÊ APPROXI}'ATÊ BOUNDARIES BENYEEN IIATERIAL TYPTS AND THT TRANSITIONS ITAY 8E GRADUAL. 6. GROUNDTVATTR IYAS NOT ENCOUI{TEREI} ¡N THE BORÍNG AÏ THE TIIIE OF DRII.IJNG. 7, I.ABORATORY TEST RESULTS¡ WC = WATER C0NTENT (r) (AsTl¡ D 2216); DD = DRY DENSITY (PCf) (ASTII D 2216)¡ -200 = PERCENTAGE PASSING N0. 200 SIEVE (AsTu D 1t1o). Fig. 2LOG OF EXPLORATORY BORING22-7-669 Kumar & Associates e {t I .8 9" SAMPLÊ 0F: Sondy Silt FROM:BorlnglO4' WC = 4.3 %, DD = 100 pcf -2OO = $g Y EXPANSION UNDER CONSTANT PRESSURE UPON WETTING x JJl¡l =tn I 2o l- o =ot1zoo x JJ t¡J-v, I zIF o Jo al1zo() I 0 *1 -2 -5 -4 f 0 -1 *2 -3 SAMPLE 0F: Sondy Silt FROM:BorlnglOl0 WC = 4.8 ?á, DD = 94 pcf NO MOVEMENT UPON WETTING -1 Fig. 322-7-669 Kumar & Associates SWËLL_CONSOLIDATION TTST RESULTS rc,tmåmfm'#ü-*TABLE ISUilMARY OF I.ABORATORY TEST RESULTSIEORING4DEPIHI5I0T{ATI.IRALtosT RECOilTENT8.64.84.394100NÆURAtDRYDENSfTY101{%}GRAVELGRÁDATIOIfr)sÆ,¡D89PERCENTPASSh{G i¡O.2msla,E65Ltc¡ulD LlnrPLASTICINDÐ(UNCONFINEÐcotPREssfiÆSTRENGTHSOILTY"EVery Sandy Silty ClaySandy SiltSandy SiltNo.221669