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Home My WebLink AboutParcel 3 Geotechnical . T. H. E. Soils Co. Inc � � Phone: (909> 678-9669 FAX: (909) 678-9769 E-mail: tl�esoilsco�c�aol.a�m � 3] 705 Central Street, Suite A• Wildomar, CA 92595 December 23, 2002 Mr. Art Coltrain 45338 Clubhouse Drive Temecula, California 92592 SUBJECT: GEOTEC�-INICAL UPDATE 1NVESTIGATION Proposed-Single-Family Residence ' � "':P � � '1_3-of-Rarcel-lVdap 24239 � Avenida De San Pasqual Temecula, Riverside County, California Work Order No. 520201.00 Dear Mr. Coltra.in: In accordance with your request, we have performed a geotechnical update investigation for the above referenced site 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 (IJBC). For this investigation, we were provided with a copy of the grading report prepared by Lakeshore Engineering (see references) and a copy of the 20-scale "Precise Grading Plan" prepared by VSL Engineering of Temecula, California. INTRODUCTION Proposed Develonment and Site Descrintion The subj ect site is currently an undeveloped mugh graded pad (Lakeshore Engineering, Inc., 1991) located along the east side of Avenida De San Pasqual north of Santiago Road (Parcel3 of Parcel Map 24239) in the city of Temecula in southwest Riverside County, California. Proposed development includes the regrading of the subject site and construction of a single-family residence with attached garage and associated driveway and landscaping. The subject site is bordered on the east, south and west by large parcel residential development and on the north by a church. The geographical relationships of the site and surrounding azea are shown on our Site Location Map, Figure 1. Topography on the ungraded portion of the subject site generally consists of moderately steep terrain with riatural gradients of approximately 30 to 40%. Drainage on the subject pad is accomplished by sheetflow generally to the west toward Avenida De San Pasqual and drainage on the ungraded portion of the parcel is toward the northwest. A deeply incised drainage course is located along the northwest boundary of the subject site. Vegetation on the subject site consisted of a low growth of annual weeds and grasses. Overall relief is approximately 80-ft. T.H.E. Soils Company, Inc. W.O. NO. 520201.00 � � � 1 �� /^/ � �"��4°'�` ��/ � • 1 � �- S � r � �� -�-` � �� }�\ ,�� 1 �� 1t'; ��'s� - � �� '. '' � ° '' �%��J�� •��' � °� /�" �`U�� Di\`- �� . �� ;'� o _ � �� l � ° . i� � `? i� i \ 0� � 4�� 1� . � � -�'�._ "��,r �=,.�� fe,=+ ,�,� �,�,�'� • _ � ♦r r � �, � _ . �� `��y-= � , ��I� � � � ' ', .�� , . �� , ,�� c•� / �.�.� ��t. i �.,�,. • 1 :,�.� � ll � �`�%., � � r i �� . 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' a � � �r l �1 � J � • � . � � - . � � —°�,-.� �` �' �f�. - ` : - __�- ., � l � : - '�,� � l �,,-�," � >—�� „ � �, � -� �:� �-T r-_ 1 � � ; � , � _ f �� l �� r�'i�� — � � . � � � "'�` .. ��'+3� � � L °'� ,� �� • � � , N � � ` ` � _ �- \ �(��.� °`•�'' \ � - —_ = "� _ � � �� O �� \� '�' �� v �\ � .- .,i� il � � � - �\� /°"�� a � �.\ r '� � � \�� " , � ...` '°\_ � , � • � /� ��, ,: � , • � .% '�� • � / � � �\\ � � �� l �- , �~ « :�y-� r �-- �r �� , �� ;� . b � �� .�. � • N`��; � � ��, , � i � � � .- � �� .�� , � ,. � . � � �� , � �� + . • Mr. Art Coltrain December 23, 2002 Page 2 SITE INVESTIGATION Back,.,�round Research and Literature Review Several published and unpublished reports and geologic maps were reviewed for the purpose of preparing this report. A complete list of these publications and reports is presented in Appendiz A. Field Investigation 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 December 16, 2002. SUBSURFACE CONDTTIONS Based on our literature review and site reconnaissance, locally, the majority of the subject site is underlain by upper Pleistocene sedimentary deposits of the Pauba Formation (Kennedy, 1977) with minor alluvial soils (American/Pacific Soils Labs, Inc. [AM/PAC], 1990) that are restricted to the undeveloped portion of site along the northwest boundary. Reportedly, the northern slope of the existing pad has been constructed of engineered fill (Lakeshore Engineering, 1991). SEISNIICII'Y 1997 UBC Seismic Update Factors specific to the subject site are as follows: The site is located approximately 3.1-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-L� in the vicinity of the subject site. The site is within Seismic Zone 4(1997 UBC Figure 16-2, Table 16-1). The near source acceleration (Na) and velocity (N�) with respect to the subject site are 1.2 and 1.47, respectively (1997 UBC Tables 16-5 and 16-`1�. The soil profile for the site is SD (1997 UBC Table 16-J). The site seismic coefficients of acceleration (Ca) and velocity (C�) aze 0.44Na and 0.64N�, respectively (1997 UBC Tables 16-Q and 16-R). T.H.E. Soils Company, Inc. W.O. NO. 520201.00 . . � Mr. Art Coltrain December 23, 2002 Page 3 Based on the above values, the coef�icient of acceleration (Ca) is 0.52 and a coefficient of velocity (C„) is 0.94 for the subject site. CONCLUSIONS Based on our document review and site reconnaissance, no significant changes to the subject site have occurred since the completion of rough grading (Lakeshore Engineering Inc., 1991). It is our opinion, the recommendations presented in the Lakeshore Engineering report are still applicable to the subject site, except where specified in this report. RECOMIl�NDATIONS General Earthwork Recommendations for site development and design are presented in the following sections of this report. The recommendations presented herein are preliminary and should be confirmed during constn�ction. Prior to the commencement of site development, the site should be cleared of any vegetation existing walkways, concrete foundations, electric lines, etc., which should be hauled off-site. The client, prior to any site preparation, should arrange and attend a meeting among the grading contractor, the design engineer, the soils engineer and/or geologist, a representative of the appropriate governing authorities as well as any other concemed parties. All parties should be given at least 48 hours notice. Preparation of Eacisting Ground 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 completely removed during benching operations. A qualified the soil engineer and/or geologist should be on- site during slope construction 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 maximum dry density (as determined by ASTM D-1557). Fill Placement 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 determine their feasibility for use as structural fill. T.H.E. Soils Company, Inc. W.O. NO. 520201.00 • � Mr. Art Coltrain December 23, 2002 Page 4 Approved fill material should be placed in 6 to 8-inch lifts, brought to at least optimum moisture content, and compacted 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 larger 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. Ezpansion Indez Testing The on-site soils are anticipated to exhibit very low expansion potential (Lakeshore Engineering, 1991). Expansion index testing should also be performed at the completion of grading and on imported soils prior to their approval as structural fill material. Final recommendations should be presented at the completion of grading. Soluble Sulfate Content Based on our past soluble sulfate content testing of similar soils on adjacent sites, it is anticipated that, from 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. Fina1 recommendation should be presented at the completion of grading. Cut-to-Fill Transition Based on our review of the proposed undated grading plan (VSL Civil Engineering), we anticipate a cut-to-fill transition across the proposed structure. 'The cut portion of the building pad should be overexcavated a minimum of 3-ft below the ground surface and extend a minimum of 5-ft beyond the building pad. 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 maximum dry density (as determined by ASTM D-1557). Foundation Svstem Design It is anticipated that the foundation elements should be founded entirely in compacted fill materials. T.H.E. Soils Company should perform a footing inspection, prior to placement of reinforcement, to insure the proposed footing excavations are in conformance with the job specifications. The structural engineer should design all footings and concrete slabs in accordance with the allowable foundation pressures and lateral bearing pressures presented for Class 3 soils on Table 18-1-A of the 1997 Uniform Building Code (UBC). The allowable foundation and lateral pressures shall not exceed the values set forth in Table 18-1-A for Class 3 soils unless data to substantiate the use of higher values are submitted. T.H.E. Soils Company, lnc. W.O. NO. 520201.00 . • Mr. Art Coltrain December 23, 2002 Page 5 Where the site is prepared as recommended, the proposed structures may bear on continuous and isolated footings. The footings should have a minimum width of 12-inches, and be placed at least 12-inches below the lowest final adjacent grade for one-story houses, with a minimum width of 12- inches, and be placed at least 18-inches below the lowest final adjacent grade for two-story houses. Footings may be designed for a maximum safe soil bearing pressure for Class 4 soils as per Table 18-1-A of the 1997 UBC for dead plus live loads. Concrete slabs, in moisture sensitive areas, should be underlain with a vapor barrier consisting of a minimum of six mil polyvinyl chloride membrane with all laps sealed. 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. Footings should be set back from the top of all cut or fill slopes a horizontal distance equal to at least'/Z 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. Differential settlements under dynamic loads of footings supported on properly compacted fill 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 parameters for imported soil may vary. Utilitv Trench Bacl�ill Utility trench backfill should be compacted to a minimum of 90 percent of the maximum dry density determined in laboratory testing by the ASTM D 1557 test method. It is our opinion that utility trench bacicfill consisting of on-site or approved sandy soils can best be placed by mechanical compaction to a minimum of 90 percent of the ma�cimum dry density. All trench excavations should be conducted in accordance with Cal-OSHA standards as a minimum. Surface Drainage Surface drainage should be directed away from foundations of buildings or appurtenant structures. All drainage should be directed toward streets or approved permanent dra.inage devices. Where landscaping and planters are proposed adjacent to foundations, subsurface drains should be provided to prevent ponding or saturation of foundations by landscape urigation water. Construction Monitoring Continuous observation and testing under the direction of qualified soils engineers and/or engineering geologists is essential to verify compliance with the recommendations of this report and to confirm that the geotechnical conditions found aze consistent with this investigation. T.H.E. Soils Company, Inc. W.O. NO. 520201.00 . • Mr. Art Coltrain December 23, 2002 Page 6 Construction monitoring should be conducted by a qualified engineering geologisdsoil engineer at the following stages of construction: • During grading operations. • Following excavation of footings for foundations. • During utility trench backfill operations. • When any unusual conditions are encountered during grading. Our investigation was performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable Geotechnical Engineers and Geologists practicing in this or similar localities. No other wazranty, expressed or implied, is made as to the conclusions and professional advice included in this 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 tlus report are valid as of the present date. However, changes in the conditions of a properly 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 appropriate 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 conditions are identified. T.H.E. Soils Company, Inc. W.O. NO. 520201.00 . • � Mr. Art Coltrain December 23, 2002 Page 7 This oppqrtunity to be of service is sincerely appreciated. If you have any questions, please call. Very truly yours, T.H.E. Soils Company, Inc. R' �o ��;'�,� Jo P. Frey Jo . inhart, RCE 23464 �g �� . � P ject Geologist Registration Expires 12/31/ > .+�.`�� • � � � �; �'a� �`�� g �� L " 0° ta �� . F�"� ��4 � �� cpir�ew: �L..-�— �� ll/�/ � `o�,, �,�'� s R. Harrison �:;�• � Project Manager � ��fi G� d.!�� :ti�� JPF/JTR/JRH:jek ACCOMPANYING MAPS, ILLUSTRATIONS, AND APPENDICES Figure � - Site Location Map (2,000-scale) APPENDIX A - References T.H.E. Soils Company, Inc. W.O. NO. 520201.00 . . . � APPENDIX A References T.H.E. Soils Company, [nc. W.O. NO. 520201.00 � • � � REFERENCES American/Pacific Soils Labs, Inc., March 21, 1990, "Percolation Investigation, Tentative Parcel Map 24239, Being a Division of Parcel 1 of Parcel Map 9428, APN 923-410-004", Project # 90- 4065. California Division of Mines & Geology, 1997, "Guidelines for Evaluating and Mitigating Seismic Hazards in California", Special Publication 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 l, 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 Margarita River Watershed, Riverside and San Diego Counties, California", Bulletin No. 91-20. Hart, E.W., 1994, "Fault-Rupture Hazard Zones in California", California Division of Mines and Geology Special Publication 42. Houston, S. L., 1992, "Partial Wetting Collapse Predictions", Proceedings of the 7th International Conference on Expansive Soils, Vol. I, pages 302-306. Intemational Conference of Building Officials (ICBO), February 1998, "Maps of Known Active Fault Near-Source Zones in California and Adjacent Portions of Nevada to be Used with 1997 Uniform Building Code" prepared by California Department of Conservation Division of Mines and Geology. International Conference of Building Officials, 1997, "Uniform Building Code". Jennings, C.W., 1975, Fault Map of California, 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, California", California Division of Mines and Geology, Special Report 131. Lakeshore Engineering, Inc., January 14, 1991, "Supplemental Compaction Testing Report Rough Grade, Parcel 1, P.M. 9428, Corner of Avenida De San Pasqual and Sierra Bonita, Rancho California, Riverside County, California", Project No. 90-24. T.H.E. Soils Company, Inc. W.O. NO. 520201.00 ' � � REFERENCES (continued) Lakeshore Engineering, Inc., March 5, 1990, "Compaction Testing Report, Proposed Single Family Dwelling, Parcels 1, 2, & 3 of P.M. 24238 Riverside County Records, Corner of Avenida De San Pasqual and Sierra Bonita, Rancho California, Riverside County, California", Project No. 90-24. Ploessel, M.R., Slosson, J.E., September, 1974, Repeatable High Ground Accelerations from Earthquakes, California Geology. Proceedings of the 7th International Conference on Expansive Soils, Volume I, "Foundations on Hydro-collapsible Soils, Pages 256-261. Rodgers, Thomas H., 1965 (fifth printing 1985), Geologic Map of California, Santa Ana Sheet", California Division of Mines & Geology, Sca1e: 1:250,000. U.S. Geological Survey, 1997, 7.5 Minute Quadrangle Map, Bachelor Mountain, California, scale 1" = 2,000'. VSL Civil Engineering, undated, "Pazcel No. 24239, Precise Grading Plan"; 20-scale, Sheet 1 of 1. T.H.E. Soils Company, Inc. W.O. NO. 520201.00