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Home My WebLink AboutSubsoil Study for Foundation Design 04.04.2017H-PryKUMAR Geotechnhal Englneedng I Englncodrq Csdogy Matedals Tcsüng J Envlronmcnlal 5020 County Road 154 Glenwood Springs, CO 81601 Phone: (970) 945-7988 Fax (970) 945-8454 Email: hpkglenwood@kumarusa.com Ofüce Localions: Parker, Glenwood Springs, and Summit County, Colorado ST'BSOIL STUDY FOR FOUNDATION DNSIGN PROPOSED RESIDENCE LOT 33, SUN MEADOTry ESTATES SOUTH MEA.DOW DRIVB GARIIIELD COUNTY, COLORADO JOB NO. t7-7-?,19 APRIL 4,2A17 PREPARED FOR: JAMES TT,IARTINEZ TO55 COUNTY ROAD 255 RIFLE, COLORADO 81650 i murti nez @ ma¡tinezwestern.com TABLE O}'CONTENTS PURPOSE AND SCOPE OF STUDY .- I - FIELD EXPLORATION ........,.,..-2. PROPOSED CONSTRUCTION FOUNDATTON BEARTNG CONDITIONS...... ................3 - DESIGN RECOMMENDATIONS .....,...........3 - FOUNDATIONS......... FLOOR SLABS...... LIMITATTONS 5 FTGURE I - LOCATICIN OF EXPLORATORY BORING FTCURE 2 - LQG OF EXPLORATORY BORING FTGURE 3 . SV/ELL-CONSOLIDATTON TEST RESULTS TABLE I. SUMMARY CIF LABORATORY TEST RESULTS ....- 4 - ....- 4 - H-P1"KUIWq¡¡ Project No. 17-7-219 PURPOSE AND SCOPE OF STUDY This report presents the results of a subsoil study for a proposed residence to be located on Lot 33, Sun Meadow Estates, South Meadow Drive, Garfield County, Colorado. The project site is shown on Figure l. 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 James Martinez dated March 3,z0n. Hepworth-Pawlak Geotechnical (now H-P/Kumar) previously performed a preliminary geotechnical study for the Sun Meadow Estates development and submitted their findings in a report dated March 28,?OW,Job No. r00 r69, A field exploration program 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 classificalion, compressibility or swell and other enginecring 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 recommendiltions and other geotechn¡cal engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The residence will be a two story wood frame structure over crawlspace with an attached gar¿lge located on the lot as shown on Figure I. The garage floor will be slab-on-grade. Grading for the structure is assumed to be relatively minor with cut depths between about 2 to 4 feet. We assume relatively Iight 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 notihed to re-evaluale the recommendations contained in this report. H-P+¡g¡g¡¡¡ Projecl No. 17-7-219 t'i -z- SITE CONDITIONS The lot is vacant and the ground surface appears mostly natural. The terrain is relatively flat with a gentle slope down to the west. Elevation difference acrûss the building site is estimated at about 2 to 4 feet. Vegetation consists of grass and weeds. FIELD EXPLORATION The field exploration for the project was conducted on March 14,2017. One exploratory boring was drilled at the location shown on Figure I to evaluate the subsurface conditíons. The boring was advanced with 4 inch diameter continuous flight augers powered by a truck-mounted CME- 458 drill rig. The boring was logged by a representative of H-P/Kumar 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 penetrâtion test described by ASTM Method D-1586. The penetration resistance values are an indication of the relative density or consisfency of the subsoils. Depths at which the samples were taken and the penetration resistance yalues are shown on the Log of Exploratory Boring, Figure 2. The samples were returned to our laboratory for review by the project engineer and testing. SUBSURFACE CONDITIONS A graphic log of the subsurface conditions encountered at the site is shown on Figure 2. The subsoils encountered, below about /r foot of organic topsoil, consist of stiff to very stiff, sandy silt and clay underlain by medium dense, very silty sand with scattered gravel and small cobbles. The upper silt and clay soils were typically calcareous, and the very silty sand soils occasionally graded to very sandy silt and €xtended down to the boring depth of 26 feet. Laboratory testing performed on samples obtained from the boring included natural moisture content and density, and percent finer than sand size gradation analyses. Results of swell- consolidation test¡ng performed on relatively undisturbed drive samples, Fresented on Figure 3, indicate low to moderate compressibility under conditions of loading and wetting. One sample H-PtKUIVAR Project No. 17-7-215 -3- (Boring I al2Vz') showed a low collapse potential and the other sample (Boring I at l0') showed a low expansion potential when wetted under a constant light surcharge. The laboratory testing is summarized in Table l. No free water was encountered in the boring at the time of drilling and the subsoils were slightly moist. TOUNDATION BEARING CONDITIONS The upper soils possess low bearing capacìty and generally tcnd to settle when wetted. Spread footings bearing on the natural soils appear feasible for foundation support with some risk of movement and distress. The risk of rnovement is primarily if the bearing soils were to become rvetted and precautions should be taken to prevent wetting. Removal and replacement of a depth af the natural soils (typically 3 to 4 Íeet\ in a moistened and compacted condition below the footings could be done to reduce the risk of foundation movement and building distress. Use of a relatively deep foundation system, such as helical piers or screw piles, that extend down to below anticipated welting depth or into less compressible soils would provide a relatively low risk of foundation movement. Provided below are recommendations for spread footings bearing on the natural soils. If recommendations for spread footings bearing on a depth of compacted structural fill or for helical piers or screw piles are desired, we should be contacted. DESIGN RECOMMENDATIONS FÛUNDATIONS Considering the subsurface conditions encountered in the exploriltory boring and the nature of the proposed construction, we believe the bu ilding can be founded with spread footings bearing on the natural soils with a risk of movement and distress. The expansion potential encountered in one of the samples can probably be neglected in the foundation design for the assumed shalloi¡rcut depths but .çhould be further evaluated at the time of excavation for the foundation. The design and construction criteria presented below should be observed for a spread footing foundation system. l) Footings placed on the undisturbed natural soils can be designed for an allowable bearing pressure of 1,500 psf. Based on experience, we expect initial settlement H.PãKUMAR Project No. 17-7-219 4 4) of footings designed and constructed as discussed in this section will be about I inch or less. There could be additional movement if the bearing soil.s were to become wetted. The magnitude of the additional movement would depend on the depth and extent of the wetting but may be on the order of I ta lYz inches. The footings should have a minimum width of l8 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 protect¡on. Placement of foundations at leåst 36 inches below exter¡or grade is typically used in this areâ. Continuous foundation walls should be heavily reinforced top and bottom to span local anomalies and better withstand the effects of some differential movement such as by assuming an unsupported length of at least 14 feet. Foundation walls acting as retaining structures should also be designed to resist ä lateral eilrth pressure corresponding to ãn equivalent fluid unit weight of at least 50 pcf. All existing fill, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the firm nûtural soils. The exposed soils in footing area should then be moistened and compacted. A representative of the geotechnical engineer should observe all fooling6) excavations prior to concrete placement to evaluate bearing conditions. FLOOR SLABS The natural on-site soils, exclusive of topsoil, should be suitable to support lightly loaded slab- on-grade construction. There may be some slab movement if the subgrade were to become wetted as discussed above. 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 controljoints 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 ofsand and gravel road base should be placed beneath slabs for support and to facilitate drainage. This material should consist of minus 2 inch aggregate with at least 507o retained on the No. 4 sieve ¿nd less than lT%o passing the No. 200 sieve. I 2) 3) s) H-P*KUMAR Projecl No. 17-V-219 -5- All f¡ll materials for support of floor slabs should be compacted to at least95Vo of maximum standard Proctor density at a moisture contenf near optimum. Required fill can consist of the on- site soils devoid of topsoil and oversized (plus 6 inch) rocks. SURFACE DRAINAGE Positive surface drainage is an important aspect of the project to prevent wetting of the bearing soils. A perimeter foundation drain around shallow crawlspace areas (less than 4 feet deep) should not be needed with adequate compaction of foundation wall backfill and positive surface slope away from foundation walls. The following drainage precautions should be observed during construction and maintained at all times after the residence has been completed: l) Inundation ofthe foundation excavations ¿nd unde¡slab areas should be avoided during construclion. 2\ Exterior backfill should be adjusted to near optimum moisture and compacted to at le¿st 95Vo of the maximum standard Proctor density in pavement and slab areas and to at least 907o 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 l2 inches in the first l0 feet in unpaved areas and a minimum slope of 3 inches in the first l0 feet in paved areas. 4) Roof downspouts and drains should discharge well beyond the limits of all backfill. 5) Landscaping which requires ¡egular heavy irrigation should be located at least l0 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 irigation. LIMITATIONS This study has been conducted in accordance with generally accepted geotechn¡cal engineering principles and practices in this area at this time. We make no warranty either express or implied. The conclusion.s and recommendations submitted in this report are based upCIn the data obtained from the exploratory boring drilled at the location indicated on Figure l, the proposed type of H.PìKUMAR Proþct No. 17-7-219 -6- 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 concemed about MOBC, then a professional in this special fTeld of practice should be consulted. Our frndings include extrapolation of the subsurface conditions identified at the exploratory boring and varialions in the subsurface conditions may not become evident until excavation is perfiormed. 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. \üe 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 rnonitor the implementation of our recommendalions, 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 of excavations and foundation bearing strata and testing of structural lill by a representative of the geotechnical engineer, Respectfully Submitted, H-P\ KU David A. Young, P.E. Reviewed by: ffi1 {}J= Steven L. Pawlak, P.E. DAY/kac H.PIKUMAR Projecl No, 17-7-219 a '': E Lol 39 âÉ71tC9191i-¡4 --"-'151"6"l0 DßIVE}^IAY PROPOSED RESIOENCE lô ll 7¡d-,-. d,-._ 1lå a6sr\ 'íj¿f o--"*P/L P L--** *-*--.. P / L^---**---'" P I L ]t 104.87 fr 1tò-' 1t ¿P ****--PlL P/L-***-*-_- Plt- s88'59'10 ff SOUTH MEÞPhI9 DRIVE 1¡ å' l/ toT 52 SUMMER MEADOW ESTATES I APPROXIMATÉ SCALE-FEEf I *l-l 1 17 -7 -219 H-PVKUMAR LOCATION OF EXPLORATORY BORING Fig. 1 t T Â- + BORINT 1 LEqEND T0P50IL; 0RGÂNIC CLAYTY SlU, FIRM, M0'5T, DARK SR0WN, 0 3r /t2 WC=8.0 DD= I 00 srLT ANo CLÄY (ML-CL), SANoY, SI{FF T0 VERY sfrFF, SLT6HTLY MOtSr, BROWN, TYPICALLY SLIGHILY CALCAREOUS. --5 t8/12 WC=5.1 DD= I 0l -200=83 sANo (sM); GRÂVTL AND VERY SILTY TO OCCASIONÀLLY VERY SANDY SILT, SCATÍERID SMAIL CO88ITS, MSDIUM DÊNSE. SLIGHTLY MOIST, BROWN. þ oRtvt sÀt¡Ptt, 2-lNcH r.0. cALrroRNtÂ uNeR sAMpLE. 177170R1Vt SAMPLE gtO\¡l COUNI. lN0lCATtS lHAi 57 8L0WS 0r A-'' ''t10-p0uN0 HAMMTR FALLTNG ¡0 f'lcHts tl/ERt REoutRto To DRtvE THt SAMPLTR I2 INCHES, ì--.10 28/t2 WC=5.9 [!=l l7 t-l¡J l¡Jf! I f o- l¡Jê -NOTESI. TIIE EXPLORATORY BORING WAS ORIILcD ON MARCH 11, ?OI7 WITH A 4-INCH OIAMTTTR CONÏINUOUS FLIGHT POWIR ÀUCTR. 1 5 37 /12 2, THT LOCAÏION OT THI E){PLORÀTORY BORING WÂ5 MTÀSURIO ÂPPRI}XIMAITLY 8Y FACII{G FROM FTÀTURES SHOWN ON IHE sIIE PLAN PR0Vr0t0. 17 /12 WC=8.5 00=1 I 6 -200=60 3. ÎHË ELTVATION OF THE TXPLORATORY SORING WAs NOI I¡TASURIO AND THT LOG OF fHE EXPLORATORY OORING 15 PLOTTTO 10 OEPTH. "20 4, THE EI(PLONATORY BORING LOCATION SHOULD 8E CONSIDTRSO ACCUTAIT ONLY TO THE OTGREE IMPLIID BY THE MEÎHOD USTO. 5. THE LINTS ETTWTTN IJATERIALS SHOWN ON THE EXPLORATORY BORING tOG RTPRTSENÎ HE APPROXIMAIT SOUNDARITS BETW€IN MÁTERIAL TYPES ANI} THI TRANSIIIONS MÂY 6E GRAÐUÄ1. 25 20/ t2 6. GROUI'IOWAITR VTÁS NOl ENCOUNTËRTD IN THT BORING Åi THÉ ÎIME OF ORILLING. 7, LABORATORY IEST RESUiÏS: l|Jc = wAttR cofrTENI (?t (A5r[4 0 22t6); DD = DRY 0ENStlY (pcr) (ASTlr{ 0 2216); -?00 = PTRCENTAGT PAsslNG N0. 200 SlËvt (ASTM 0 ll40). I r t-" I I I Ir^ Jo 17 -7 -219 H.PryKUMAR LOG CIF EXPLORATORY BORING Fig. 2 J 1 o N -l JJl¡,!tlt -¿ I zo {6 Jo!-aoo -q -6 ? I 0 -l -2 r.0 - t(sF 100 ¡s JJ a¡J3tlt I If- Õ Joutzo(J t0 SAMPLE OF: Sondy Slll ond Cloy FROM:Boring 1 ç 2.5' WC = 8.0 Z. 0D = too pcf ADDITIONAL COMPRESSION UÑOgR CONSTANT PRESSURE OUE IO WETTING I I i SAMPLE OF: Sondy Silty Cloy FROM:Boring 1O t0' WC = 5.9 %, tt = 117 pcf i J I I i ì t t I-'i ! I ì I i I I ¡ l I I I I I ¡ ì l I ; I I i1 jj il!ll; 1i¡rritlrl iìilÌr I I I I I I j II I i .-t I EXPANSION UNDER CONSTANT PRESSURE UPON WETTING I I J I I { I I I 1 t I 1 I I I t7 -7 -219 H-PryKUMAR SWELL-CONSOLIDATION TEST RESULT Fï9. 3 H-P*KUMARTABLE 1SUMMARY OF LABORATORY TEST RESULTSProJect No. 17-7-219SOIL TYPESandy Silt and ClaySandy Silt and ClaySandy Silty ClayVery Sandy Silt withGravelUNCONFINEDcofitPREsstvESTRENGTHfPSRPLASI|CINDEXf/"1LIQUIDLtiltTlo,l"lPERCEÌ.¡TPASSINGNO.200stËvE8360SAND(%lGRAVELl"/.)NATURALDRYDENSIfYfocfì100l0rlt7I t6NATURALMOISTURÉCONTENT16/"\8.05.35.98.3DÊPTHtRt2%5t02ABORINGI