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Home My WebLink AboutSubsoil Study for Foundation Design 06.29.18H-PryKUMAR Geotdrnlcal Eng¡noering I Englneedng Gsology Metod¿ús Tesüng I Environmental 5020 County Road 154 Glenwood Springs, C0 81601 Phone: (970) 945-7988 Far (970) 945-8454 Email: hpkglenwood@kumarusa.com Office Locations: Denver (HQ), Parker, Colorado Springs, Fort Collins, Glenwood Springs, Summit County, Colorado ST]BSOIL STTJDY FOR FOUNDATION DESIGN PROPOSED RESIDENCE LOT 30, FIRST EAGLES POINT 21l EAGLE RIDGE DRTVE BATTLEMENT MESÄ, COLORADO PROJECT NO. 18-7-381 JUNE 29,2018 PREPARED FOR: DANIEL GARDNER 134 COUNTY ROAD 303 PARACHUTE, COLORADO E1635 danielcgardner@ exc.com TABLD OF CONTENTS PURPOSE AND SCOPE OF STUDY PROPOSED CONSTRUCTION STTE CONDITIONS FMLD EXPLORATION.. SUBSURFACE CONDITIONS FOLTNDATION BEARING CONDITIONS DESIGN RECOMMENDATIONS .. FOUNDATIONS FLOOR SLABS PERMETER DRAIN SURFACE DRAINAGE ... LIMMATIONS FIGURE 1 - LOCATION OF EXPLORATORY PTTS FIGURE 2 - LOGS OF EXPLORATORY PITS FIGURES 3 and 4 - SWELL-CONSOLIDATION TEST RESULTS FIGURE 5 - GRADATION TEST RESULTS TABLE I- SUMMARY OF LABORATORY TEST RESULTS 1 ..- I - 1 ..-2- -2- -2- 3 3 4 4 5 5 H.PÈKUMAR Project No. 18-7-38'l PURPOSE AND SCOPE OF STUDY This report prescnts the rcsults of a subsoil study for a proposed residence to be located on Lot 30, First Eagles Point, atZll Eagle Ridge Drive, 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 sfudy was conducted in accordance with our agreement for geotechnical engineering services to Daniel Gardner dated May 30, 2018. A field exploration program consisting of exploratory pits 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 recommendations and other geotechnical engineering considerations based on the proposed construction and the subsurface conditions encountered. PROPOSED CONSTRUCTION The proposed residence will be an approximately 1,600 square foot single-story wood-frame structure with an attached garage. Ground floor will be structural over a crawlspace in the residence and slab-on-grade in the garage. Grading for the structure is assumed 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 report. SITE CONDITIONS The subject site is curently vacant. Topography at the site is a mesa top with generally gentle slopes down to the northwest. Vegetation at the site consists of native grass and sparse weeds. There is around r/zfoot of elevation difference across the proposed building area. H-P\KUMAR Project No. 18-7-381 FIELD EXPLORATION The field exploration for the project was conducted on June 6, 2018. Two exploratory pits were excavated at the locations shown on Figure I to evaluate the subsurface conditions. The pits were dug with a rubber-tired backhoe. The pits were logged by a representative of H-p/I(umar Samples of the subsoils were taken with relatively undisturbed and dìsturbed sampling methods. Depths at which the samples were taken are shown on the l-ogs of Exploratory Pits, 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 Z. The subsoils consist of about ZVz ta 7 feet of sandy silt and clay overlying relatively dense gravel and sand with cobbles down to the maximum depth explored of 8 feet in Pit I and íyzfeet in pit 2. Digging in the dense granular soils was difficult due to the cobbles and boulders and digging refusal was encountered in the deposit Laboratory testing performed on samples obtained from the borings included natural moisture content and gradation analyses. Results of swell-consolidation testing performed on relatively undisturbed drive samples of the sandy clay and silt, presented on Figures 3 and 4, indicate low compressibility under light loading and a low to moderate collapse potential (settlement under constant load) when wetted. The samples were moderately compressible under increased loading after wetting. Results of gradation analyses performed on a disturbed sample (minus l/z inch fraction) of the coarse granular subsoils are shown on Figure 5. The laboratory testing is summarized in Table l. No free water was encountered in the pits at the time of excavation and the subsoils were slightly moist. FOUNDATION BEARING CONDITIONS The upper fine-grained soils encountered at the subject site generally possess low bearing capacity and a low to moderate settlement potential. A spread footing foundation system appears H-P\KUMAR Proiecl No. 18-7-381 -3- feasible with some risk of post construction settlement on the order of up to about I to Z inches Bearing in the underlying gravel soils or structural fill would provide a lower risk of settlement Recommendations for a shallow spread footing foundation system are presented below. DESIGN RECOMMENDATIONS FOUNDATIONS Considering the subsurface conditions encountered in the exploratory pits and the nature of the proposed construction, we recommend the building be founded with spread footings bearing on the natural gravel soils or on structural fill. The design and construction criteria presented below should be observed for a spread footing foundation system. 1) Footings placed on the undisturbed gravel soils should be designed for an allowable bearing pressure of 2,000 psf. Based on experience, we expect settlement of footings designed and constructed as discussetl in this section will be less than I inch. Where the upper tìne-grained sandy silt and clay soils are encountered at design footing grade, we recommend that the silt and clay be removed down to the natural gravel subsoils. The footing grade can be lowered to bear on the gravel soils or structural fill can be placed to reestablish design footing grade. 2) The footings should have a minimum width of 18 inches for continuous walls and 2 feet for isolated pads. 3) 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 area. 4) 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 also be designed to resist a lateral earth pressure coffesponding to an equivalent fluid unit weight of at least 55 pcf. H-PÈKUIVIAR Project No. 18-7-381 4 s)All existing sandy clay and silt, topsoil and any loose or disturbed soils should be removed and the footing bearing level extended down to the relatively dense gravel soils. The exposed soils in footing area should then be moistened and compacted. If designed, structural fill consisting of imponed %-inch road base can be placed to re-establish design footing grade, Structural fill should be placed at near optimum moisture content and be compacted to at least gg%o of the maximum standard Proctor density. A representative of the geotechnical engineer should observe all footing excavations prior to concrete placement to evaluate bearing conditions and perform compaction testing on all structural fill placed for support of footings. FLOOR SLABS The natural on-site soils, exclusive of topsoil, are suitable to support lightly 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 forjoint 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 slabs to provide support. This material should consist of minus 2 inch aggregate with at least 50Vo retained on the No. 4 sieve and less than ZVo passing the No. 200 sieve. All fill materials for support of floor slabb should be compacted to at least gSVo of maximum standard Proctor density at a moisture content near optimum. Required fill can consist of the imported 3/¿-inch road base devoid of vegetation, topsoil and oversized rock. PERIMETER DRAIN A foundation perimeter drain should not be required in shallow crawlspace areas (less then 4 feet deep) provided foundation wall backfill is adequately compacted and surface drainage recommendations are followed. 6) H-P\KUMAR Proiect No. 18-7-381 5 SURFACE DRAINAGE The following drainage precautions should be observed during construction and maintained at all tirnes after the residence lns been completed: l) Inundation ofthe 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 95Vo of the maximum standard Proctor density in pavement and slab areas and to at least 90Vo of the maximum standard Proctor density in landscape areas. 3) The ground surface surounding the exterior of the building should be sloped to drain away from the foundation in all directions. Vy'e 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 10 feet in paved areas. Free-draining wall backfill (if any) should be capped with about 2 feet of the on-site 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 irigation 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 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 pits excavated at the locations 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 interpolation and extrapolation of the H-P\KUMAR Project No. 18-7-381 -6- subsurface conditions identified at the exploratory pits 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 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 monitor the implementation 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 of excavations and foundation bearing strata and testing of structural fill by a representative of the geotechnical engineer. Respectfully Submitted, ,rMr,t/- Robert L. Duran, E. I. Reviewed by: ¿2' Ðaniel E. Hardin, RLD/kac cc: Amy Perrin (amyleepenin@gmail.com) 4 '7 ¡\:L 0 t aI ..?- H-P*¡191y¡¡¡Project No. 18-7-381 rÀrJ5 It"ç¡.-stNrrlc)t-Irlãc,6)moÐrrlhft*tHtFttF=frooP(rltr:9ln{s-tIq3*fåt,tl'tJltrltÇtlå,*.vlhs"|H\\I\\\\,flr_å'ot*\\\Þì\\tt-Ê'\\\\\$\¡\{.\f\$\\\.s\\\\1\,lt\-!\\\\\!+stt\*Ê..luhs*{\l\r\hÈ."t\\\-D!¡toX=-lmU1C)rmI-¡t-flÍrl.{\\\¿"û\æII(¡æ-.LIT<'^c3nroc)Þ-l()zoTlmXTronÞ'do7T-lu)Tl(o "1 ,€ PIT 1 EL. 1 00'Pt't 2 EL. 100.5' 0 5 WC=1 1.8 DD=77 WC=9.6 DD=67. -20Q=27 WC=5.3 DD=95 o 5 10 F-t¡J t¡J lL I-F(L IJo F L¡J L¡JL I-¡- Ã- l¡Jô -ì -l WC=5.3 *4=37 -200=30 t0 LEGEND +4 = PERCENTAGE RETAINED ON NO. 4 SI -200 = PERCENTAGE PASSTNG NO. 200 St þ I CLAY AND SILT (CL-ML): SANDy, ST|FF, SL|GHTLY MOIST, BROWN GRAVEL AND COBBLES (GM_SM): SANDY, SILTY, DENSE, SLIGHTLY MOIST. TAN. HAND DRIVEN LINER SAMPLE. DISTURBED BULK SAMPLE I enlcrrcAl BAcKHoE REFUSAL. NOTES 1. ÏHE EXPLORATORY PITS WERE EXCAVATED WITH A BACKHOE ON JUNE 6, 2018. 2. THE LOCATIONS OF THE EXPLORATORY PITS WERE MEASURED APPROXIMATELY BY PACING FROMFEATURES SHOWN ON THE SITE PLAN PROVIDED. 3. THE ELEVATIONS OF THE EXPLORATORY PITS WERE MEASURED BY HAND LEVEL AND REFER îOTHE ELEVAÎION OF PIT 1 AS I OO.O FEET. 4. THE EXPLORATORY PIT LOCATIONS AND RELATIVE ELEVATIONS SHOULD BE CONSIDEREDACCURATE ONLY TO THE DEGREE IMPLIED BY THE .METHOD USED. 5. THE LINES BETWEEN MATERIALS SHOWN ON THE EXPLORATORY PIT LOGS REPRESENT THEAPPROXIMATE BOUNDARIES BETWEEN MATERIAL TYPES AND THE TnIÑiITio¡Ti.i¡Iv ae GRADUAL. 6. GROUNDWATER WAS NOT ENCOUNTERED IN THE PITS AT THE TIME OF OIGGING. PITS WEREBACKFILLEO SUBSEQUENT TO SAMPLING. 7. LABORATORY TEST RESULTS: WC = WATER CONTTNT (%) (ASTM D 2216); DD = DRy DENS|TY (pcr) (asru D 2216); EVE (ASTM D a22); EVE (ASTM D il40) o 1 8-7-381 H-PryKUMAR LOGS OF EXPLORATORY PITS Fig. 2 Ë a 4 1 SAMPLE OF: Sondy Sill with Scollerod Grovel FROM:Pitl@4' WC = 11.8 %, DÐ = 77 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE DUE TO WETTING Il i:;t :1 :. r¡th o¡frfrlhc, s¡dl iî cl i4 ! : 2 0 N -2 JJl¡¡ =tt7 I zo¡- o Jov,zoo -4 -6 -8 0 -12 -14 -16 r.0 t0 1 8-7-381 H-PVKUMAR SWELL-CONSOLIDATION TIST RESULTS Fí9. 3 : { I ã SAMPLE OF: Sondy Silt ond Ctoy FROM:Pit2lÐ2' IVC = 5.5 %, Dù = 95 pcf ADDITIONAL COMPRESSION UNDER CONSTANT PRESSURE OUE TO WETTING sñd{dú[ not tÉl aoûV hùarl9 €ducld, ItE rdttø¡aGi¡t6.iûet olo¡¡eml cd l¡c.sdt h r-..,i ,r - ---- ,- JJl¿j3 ar7 I zo|- Õ JotnzorJ 0 -1 -2 -5 -4 -5 -6 t.0 - KSF r0 r00 1 8*7-381 H.PryKUMAR SWTLL-CONSOLIDATION TTST RESULTS Fig. 4 È - -i SIEVE ANALYSIS lrrE ¡E^¡rÈos 2a HRs t Hns u.s, srSoARo 3ERt:s CLEAR SOUME OP€HIflGS \ lfq' t/.' 1 t/2' I / I I I I I I I I I I l I I I I t tl SAND GRAVEL -_l_,- --_r I I FINE MEDIUM FI¡IE COARSE HYOROMETÉN AilALYSIS T EI r00 ¡o ùo 70 co 50 ao vt 20 to o lo 20 30 40 5C ıo ta ao to loo t Ë DIAMETER OF CLAY TO SILT COBBLES GRAVEL 37 X SAND J3 '(SILT ANO CLAY 30 X SAMPLE OF: Sllty Grovcl ond Sond FROMI Plt 1Q7'-7.5' tharó tctl.rrullr applt only lo lh.tomplor rhlch u.r. ta¡i.d. ThrItrllng raport rholl nol b. r.p.oducrd,arccpt ln lull. rllhout lh. r.lHcnqpp¡ovol ot Kumor t A¡eclolr¡, lnc,Sio. oñol¡h h¡tlng h pt¡lormtó lnoccordoncc rllh ASTI¡ 0422. ASfH Ct36ondlor ASTil Dlt,lo. 1 8-7-58 1 H-PVKUMAR GRADATION TEST RESULTS Fig. 5 H=P*KUMAR$HffiMåRV 8FrEgT RFgHhTgËrateet NB: 1fi:l:ãä1qilriflsf,s HtlËSILWFEfL(Fffi*8(V.l-*TTrfEñBErffipWtr11{HVflÈåNHT:EHNHfi¡\8HåVÊt44148E(pct),WTtrâ1tqf%ìüffiffiäI8€q.T'làl.I - JYz{ft}BËËTHATTËiHãMþEFFIT