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Home My WebLink AboutLimited Geotechnical Update Mar.3, 2003~ r T. H. E. Soils Co., In~ ~ ~'~ z-~ Phone: (909) 678-9669 FAX: (909) 678-97G9 317p5 Central Street, Suite A• Wildomar, CA 92595 March 3, 2003 Mr. Yogesh N. Goradia 3500 I.omita #M250 Torrance, California 90505 SUBJECT: LIMITED GEOTECFINICAL UPDATE INVESTIGATION Proposed Residential Development Approximately Northem Two-Tlvrds of Tract 25004 Temecula, Riverside County, California Work Order No. 549301.00 Dear Mr. Goradia: E-maiL• thesoilsconaol.com In accordance with your request, we have performed a limited geotechnical update investigation for the above referenced Tract 25004 (northem two-thirds) in Temecula, California. The purpose of our investigation was to update the original geotechnical recommendations (see references) and to provide a seismic update based on the 1997 Uniform Building Code (UBC). For this investigation, we were provided with a copy of the "Geotechnical Report" prepared by South Coast Geological Services, Inc (SCGS) and a copy of the 100-scale topographic "Tentarive Tract Map" prepared by A.J. Terich Engineering of Temecula, Califomia (see references). INTRODUCTION Prooosed Develonment and Site Descriorion The subject site is currently vacant and is located between Murrieta Hot Springs Road on the north and Andrews Way on the south in the city of Temecula in southwest Riverside County, California. The proposed development includes typical cuUfill 8rading of the subject site for conshvction of a single-family residential hact with associated street improvements and an open space area on the northwest corner of the site. The subject site is bordered on the north by Mumeta Hot Springs Road and residential development, on the west by vacant undeveloped land, on the south by an existing single-family residential development (south one-third of Tentative Tract 25004), on the east by vacant undeveloped land and lazge pazcel residenrial development. The geographical relationships of the site and surrounding area are shown on our Site Location Map, Figure 1. Topographically, the subject site is comprised of rolling hills and ridges, which increase in elevation and steepness to the north at a prominent knoll. Two steep-sided narrow valleys with tributary guliies trend west to southwest across the northem portion of the site. T.H.E. Soils Compeny, lnc. W.O. NO. 549301.00 T.H.E. Soils Co.,Tnc. Plionc: (9091678-9669 FAX: (909) 67R-9769 i1~0~ Ccntr~l Strect, Suitc A•\~Idamar, CA 92595 :~, <~ , ";iis' ~: ~, I~. ~'~ ~.~ ; ; , -, ,,o :, _ ~. _ ` _ , _. L9_j i - r,.~ ,, .: , S. ,,, =; _ ~"°= ,<.~ ~ , ~'~:c~_ -.~ ADAPTED FROM A 7.5 MINUTE U.S.G.S. MAP- BACHELOR MTN., CA., 1978 lQ `-~ ~ ',~-~ ° \\ ~'~ ~=~~ o l ~ ~ a 4~ ~i 6-~ ~ ~ ;..c 0 1000 2000~ 3000 0000 SITE LOCATION MAP w.o.# 549301.00 DQ1e! MARCH 2O03 Figure: ~ z.. ~ ~ Mr. Yogesh N. Goradia March 3, 2003 Page 2 Reportedly, a wood-frame house and barn, as well as severa( mobile homes and utility sheds, were formerly located on the existing cut and/or fill pads on the site (SCGS, Inc., 1989). Foundations for the house and several of the former structures were observed on the northem portion of the subject site along with numerous construction debris and trash. Vegetation on the subject site consists predominately of a new growth of annual weeds and grasses and several large omamental trees in the vicinity of the former residence and out buildings. The San Diego Aqueduct trends generally north-south beneath the eastern and north-central portions of the subject site in a Metropolitan Water District (MWD) easement. STTE INVESTIGATION Backeround Research and Literature Review Several published and unpublished reports and geologic maps were reviewed for the purpose of preparing ttvs report. A complete list of these publications and reports is presented in Appendia A. Field Investieation No subsurface exploration was perFormed as part of our update investigation. Our senior geologist conducted a field reconnaissance and geologic mapping of the subject site on Friday, February 28, 2003. SUBSURFACE CONDITIONS Based on our literature review and site reconnaissance, locally, tha majority of the subject site is underlain by upper Pleistocene sedimentary deposits of the Pauba Formation (Kennedy, 197'n with minor alluvial soils and ganitic bedrock on the northem portion of the site (SCGS, Inc., 1989.). SCGS, Inc. mapped minor amounts of undceumented fill across the site including the eacisting pads. SEISNIICITY Reeional Seismicitv The site is located in a region of generally high seismicity, as is all of southem California. During its design life, the site is expected to experience strong ground motions from ea~thquakes on regional and/or local causative faults. The subject property is not located in a State of California Fault-Ruptute Hazard Zone for ac6ve faulting (Hart, 2001). No active faults aze known to traverse the site (Kennedy, 1977). . The closest known zoned active fault is the Elsinore Fault Zone (Glen Ivy) located about 73-kilometers to the southwest. Kennedy has mapped an inferred extension of the east trending Murrieta Hot Springs Fault Zone approximately 900-ft north of the subject site (SCGS, Inc., 1989). Kennedy has mapped a short T.H.E. Soils Company, Inc. W.O. NO. 549301.00 2 J i Mr. Yogesh N. Goradia March 3, 2003 Page 3 ~ splay off the Murrieta Hot Springs Fault Zone trending east-northeast through the properry, about 500-ft south of the northern property line. Kennedy indicates late Pleistocene activity on this segment. SCGS, Inc. (1989) excavated an exploratory trench that was appmximately 210-ft long and as much as 12-ft bgs across the mapped fault splay. No geologic evidence for recent faulring was found (SCGS, Inc., 1989). 1997 UBC Seismic Uadate Factors specific to the subject site are as follows: The site is located appmximately 73-kilometers to the northeast from the Elsinore fault (Glen ivy) (ICBO, 1998). The Elsinore fault (Glen ivy) is reported as a Type B fault (ICBO, 1998; and 1997 UBC Table 16-in in the vicinity of the subject site. The site is within Seismic Zone 4(1997 UBC Figure 16-2, Table 16-1). The soil profile for the site is Sp (1997 UBC Table 16-~. The neaz source acceleration (Ne) and velocity (N~) with respect to the subject site are 1.0 and 1.1, respectively (1997 UBC Tables 16-5 and 16-'1~. The site seismic coefficients of acceleration (Ca) and velocity (C~) are 0.44N8 and 0.64N~, respectively (1997 UBC Tables 16-Q and 16-R). Based on the above values, the coefficient of acceleration (Ce) is 0.44 and a coefficient of velocity (C~) is 0.704 for the subject site. Liauefaction - Secondarv Seismic Hazards The azea proposed for the subject site is underlain by medium dense to dense sedimentary and granitic bedrock and no groundwater was encountered during a previous geotechnical investigation of the subject site (SCGS, Inc., 1989). No known active fault has been mapped or found on the subject site (SCGS, Inc., 1989). The subject site is located in an area tUat is free of large rock and no landslides have been mapped on the subject site (Kennedy, 1977 & SCGS, Inc., 1989) or were noted during aze aerial photograph review. The proposed shvctures aze anticipated to be founded entirely in dense bedmck materials or engineered fill compacted to 90% of the dry density as deternvned by ASTM-Test Method D-1557. Due to the above, the potential for secondary seismic I~azards including liquefaction, ground rupttu~e, landslides, rockfall, tsunamis, and seismically induced soil settlement aze considered unlikely. T.H.E. Soils Company, Inc. W.O. NO. 549301.00 ~ ~ ~ Mr. Yogesh N. Goradia Mazch 3, 2003 Page 4 Based on our document review and site reconnaissance, no significant changes to the subject site have occurred since the comple6on of the preliminary geotechnical report (SCGS,1nc., 1989). It is our opinion, the recommendations presented in the SCGS, Inc. report aze still applicable to the subject site, except where specified in this report. RECOMMENDATIONS General Earthwork Recommendations for site development and design are presented in the following secfions of this report. The recommendations presented herein aze preliminary and should be coniinned during conshvction. Prior to the commencement of site development, the site should be cleazed of any vegetation existing walkways, septic tanks, leach lines, concrete foundations, electric lines, etc., which should be hauled off-site. The client, prior to any site preparation, should amdnge and attend a meeting among the gtading contractor, the design engineer, the soils engineer and/or geologist, a representative of the appropriate governing authorities as well as any other concerned parties. All parties should be given at least 48 hours notice. Preaararion of Egistine Ground All alluvial soils and undocumented fills should be removed prior to placement of fill materials and may be reused as fill materials pmvided they are free of construction debris and non-expansive. Depths of removals within the alluvial soils and undocumented fills are anticipated to be a miniinum of 5 and 8-ft, respectively (SCGS, Inc., 1989). The project soils engineer and/or geologist should verify the depth of removals in the field. Fill slopes should be properly keyed and benched in accordance with the UBC. The keyway should extend a minimum of 1 ft. into either competent bedrock material or engineered fill materials and tilted a minimum of 2% into the hillside. Any colluvium or loose soils should be complete(y removed during benching operations. A qualified soil engineer and/or geologist should be on-site during slope constniction and earthwork operations to assure that proper grading techniques, keyway development, and benching are accomplished Prior to placement of fill materials, the exposed earth materials should be scarified, moisture conditioned, and recompacted to a minimum of 90-percent of the maxunum dry density (as determined by ASTM D-1557). T.H.E. Soils Company, Inc. W.O. NO. 549301.00 ~ • Mr. Yogesh N. Goradia March 3, 2003 Page 5 Fill Placement s On-site sedimentary bedrock and compacted fill are expected to be suitable for use as structural fill provided they are non-expansive. A qualified soil engineer should test import materials to deternvne their feasibility for use as structural fill. Approved fill material should be placed in 6 to 8-inch lifts, brought to at least optimum moisture content, and c,ompacted to a minimum of 90 percent of the maximum laboratory dry density, as determined by the ASTM D 1557 test method. No rocks, chunks of asphalt or concrete lazger than 6 inches in diameter should be used as fill material. Rocks larger than 6 inches should either be hauled off-site or crushed and used as fill material. Cut/Fill Transitions Cut-to-fill tcansitions should be eliminated &om building pads where the depth of fill exceeds 12- inches. This should be accomplished by overexcavating the cut portion and replacing the materials as pmperly compacted fill. Limits of excavation should be verified by the project civil engineer. Recommended depths of overexcavation are as follows: Depth of Fill on "Fill" Portion 0 to 6-ft > 6-ft Depth of Overexcavation "Cut" Portion 3.0-ft %2 Depth of Fill to Ma~cimum Depth of 15-ft Expansion Indea Testine The on-site soils are anticipated to exhibit very low expansion potential (SCGS, Inc., 1989). Expattsion index testing should also be performed at the completion of grading and on imported soils prior to their approval as structural fill material. Final recommenda6ons should be presented at the complerion of grading. Soluble Salfate Content Based on previous soluble sulfate content testing of the on-site soils (SCGS, In., 1989), it is anticipated that, &om a corrosivity standpoint, Type II Portland Cement can be used for construction. Sulfate content testing should be conducted within the building pads at the completion of grading and on imported soils prior to their approval as structural fill material. Final recommendations should be presented at the compleUon of grading. T.H.E. Soils Company, Inc. W.O. NO. 549301.00 ~ ~ ~ Mr. Yogesh N. Goradia March 3, 2003 Page 6 Foundation Svstem Desit~n Foundarion elements should be placed en6rely either in medium dense to dense bedrock materials or engineered fill compacted to a minimum of 90 percent of the maximum dry density. For one- story houses, continuous spread footings should be a minimum of 12-inches wide and 12-inches below the lowest adjacent grade. For two-story houses, continuous spread footings should be a minimum of 12-inches wide and 18-inches below the lowest adjacent grade. As a minimum, all footings should have one No. 4 reinforcing baz placed at the top and bottom of the footing. Concrete slabs, in moisture sensitive areas, should be underlain with a vapor bazrier consisting of a m~n;,,,um of six mil polyvinyl chloride membrane with all laps seated. A 2-inch layer of clean sand should be placed above the moisture barrier. The 2-inches of clean sand is recommended to protect the visqueen moisture barrier and aid in the curing of the concrete. The structural engineer should design all footings and concrete slabs in accordance with the anticipated loads and the soil parameters given. Footings should be set back from the top of all cut or fill slopes a horizontal distance equal to at least Yz the vertical slope height with a minimum setback of at least 5-ft. Total settlements under static loads of footings supported on in-place bedrock materials and sized for the allowable bearing pressures are not expected to exceed about 1/2 to 3/4 of 1 inch for a span of 40-ft. Differential settlements under dynamic loads of footings supported on properly compacted fill materials or bedrock materials and sized for the allowable bearing pressures aze not expected to exceed 1/4-inches for a span of 40-ft. These settlements are expected to occur primarily during construction Soil engineering parameteis for imported soil may vary. Utilitv Trench Backfill Utility trench backfill should be compacted to a min;mum of 90 percent of the maximum dry density determined in laboratory testing by tl~e ASTM D 1557 test method. It is our opinion that ufility trench backfill consisting of on-site or appmved sandy soils can best be placed by mechanical compaction to a minimum of 90 percent of the maJCimum dry density. All trench excavations shouid be conducted in accordance with Cal-OSHA standards as a minimum. Surface Drainaee Surface drainage should be directed away from foundarions of buildings or appurtenant structures. All drainage should be directed towazd streets or approved permanent drainage devices. Where landscaping and planters are proposed adjacent to foundations, subsurface drains should be provided to prevent ponding or saturation of foundations by landscape irtigation water. T.H.E. Soils Compmiy, Inc. W.O. NO. 549301.00 ~ ~ ~ Mr. Yogesh N. Goradia Mazch 3, 2003 Page 7 Construction Monitorine Continuous observation and testing under the direcfion of qualified soils engineers and/or engineering geologists is essential to verify compliance with the recommendations of tlus report and to confirm that the geotechnical conditions found are consistent with this investigation. Construction monitoring should be conducted by a qualified engineering geologisUsoil engineer at the following stages of construction: • During grading operarions including alluvial nemovals, benching and keyway excavations. • Following excauation of footings for foundations. • During utility h~ench backfill operations. • When any unusual conditions are encountered durin~ Srading• Our investigation was performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable Geotechnical Engineers and Geologists pracricing in this or similaz localities. No other wam~nty, expressed or implied, is made as to the conclusions and professional advice included in tlus report. The samples taken and used for testing and the observations made are believed representative of the entire project; however, soil and geologic conditions can vary significantly between test locations. The findings of this report are valid as of the present date. However, changes in the conditions of a property can occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacent properties. In addition, changes in applicable or appmpriate standards may occur, whether they result from legislation or the broadening of knowledge. Accordingly, the findings of this report may be invalidated wholly or partially by changes outside our control. Therefore, this report is subject to review and revision as changed condi6ons ate identified. T.H.E. Soils Company, Inc. W.O. NO. 549301.00 8 ~ Mr. Yogesh N. Goradia Mareh 3, 2003 Page 8 ~ This opportunity to be of service is sincerely appreciated. If you have any questions, please call. Very truly yours, T.H.E. Soils Company, Inc. /' ~/ J P. Frey ject Geologist d John . Reinhart, RCE 2_ Registration Expires 12/3 ~.~~ ~a~~~` n 5~ ~ ~~ l,~z~~~l~ ames R. Harrison Project Manager JPF/7TR/JRH:jek ACCOMPANYING MAPS. ILLUSTRATION~ AND APPENDICES Figure 1- Site Location Map (2,000-scale) APPENDIX A - References T.H.E. Soils Company, lna W.O. NO. 54930L00 ~ ~ APPENDIX A References ~ T.H.E. Soils Compeng Inc. W.O. NO. 549301.00 `~ ~ REFERENCES ~ A.J. Terich Engineering, December 1998, "Tentative Tract No. 25004"; 100-scale, Sheet 1 of 1. Califomia Division of Mines & Geology, 1997, "Guidelines for Evaluating and Mitigating Seismic Hazards in Califomia", Special Publicafion 117. California Division of Mines & Geology, 1996, "Probabilistic Seismic Hazard Assessment for the State of California", DMG Open File Report 96-08, USGS Open File Report 96-706. California Division of Mines & Geology, 1990, "State of California Special Studies Zone - Murrieta, California Quadrangle", Revised Official Map - Effective January 1, 1990, Scale: 1-inch = 2,000-ft. Coduto, Don, P., 1994, "Foundation Design Principles and Practice", Prentice Hall, pages 637-655. Department of Water Resources, August 1971, "Water Wells and Springs in the Western Part of the Upper Santa Mazgarita River Watershed, Riverside and San Diego Counties, California", Bulietin No. 91-20. Hart, E.W., 2001, "Fatilt-Rupture Hazard Zones in California", Califomia Division of Mines and Geology Special Publication 42, CD-ROM Version. Houston, S. L., 1992, 'Partial Wetting Collapse Predictions", Proceedings of the 7th Intemarional Conference on Expansive Soils, Vol. I, pages 302-306. International Conference of Building Officials (ICBO), Febniary 1998, "Maps of Known Acrive Fault Neaz-Source Zones in Califomia and Adjacent Portions of Nevada to be Used with 1997 Uniform Building Code" prepared by California Department of Conservation Division of Mines and Geology. Internafional Conference of Building Officials, 1997, "Uniform Building Code". Jennings, C.W., 1975, Fault Map of Califomia, California Division of Mines and Geology, Geologic Data Map No. 1. Kennedy, Michael P., 1977, "Recency and Character of Faulting Along the Elsinore Fault Zone in Southern Riverside County, Califomia", Califorcria Division of Mines and Geology, Special Report 131. Ploessel, M.R, Slosson, J.E., September, 1974, Repeatable High Ground Accelerations from F,arthquakes, Califomia Geology. Proceedings of the 7th Intemational Conference on Expansive Soils, Volume I, "Foundations on Hydro-collapsible Soils, Pages 256-261. TN.E. Soils Company, Inc. W.O. NO. 5493DI.00 ' 1 ~ ~ REFERENCES (continued) Riverside County Planning Department, 1990, "Seismic/Geologic Hazard, Project No.89118.1, Tentative Tract 25005, APN No. 914-260-O1 Q County Geologic Report N. 677, Rancho California Area", Dated January 17, 1990. Rodgers, Thomas H., 1965 (fifth printing 1985), Geologic Map of California, Santa Ana Sheet", California Division of Mines & Geology, Scale: 1250,000. South Coast Geological Services, Inc., October 23, 1989, "Geotechnical Report for a Pmposed Subdivision Consisting of I15, Single-Family Homes Within the 59-Acre Parcel Described as Tentative Tract No. 25004", Project No. 891181. U.S. Geological Survey, 1978, 7.5 Minute Quadrangle Map, Bachelor Mountain, Califomia, scale 1" = 2,000'. AERIAL PHOTOGRAPHS UTILIZED XEAR/SCALE FLIGHT #/FRAME # AGENCY 1962/1 "=2,000' Co. F1ighU3-397,3-398 Riv Co Flood Control 1974/1 "=2,000' Co. F1ighU878,879 Riv Co Flood Control 1980/1 "=1,600' Co. F1ighU907,908 Riv Co Flood Control 1983/1 "=1,600' Co. F1ighU399,400 Riv Co Flood Control 1990/1"=1,600' , Co. F1ighU17-24,17-25 Riv Co Flood Control T.H.E. Soils Compairy, Inc. W.O. NO. 549301.00 1 Z l