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HomeMy WebLinkAboutGeotechReportRoughGrading(Jan.3,2007) I I I I I I I I I I I I I I I II i I I I I:maIINLAND. INC. Geotechnical, Environmental, and Material Testing Consultants GEOTECHNICAL REPORT OF ROUGH GRADING, REAR-YARD EXTENSION OF LOTS 1,2,3, AND 5 OF TRACT 23513, CITY OF TEMECULA, RIVERSIDE COUNTY, CALIFORNIA Project No. 104721-30 Dated: January 3, 2007 Prepared For: Mr. David R. Meade GALLERY DEVELOPMENT 31618-1 Railroad Canyon Road Canyon Lake, California 92587 \ 41531 Date Street. Murrieta. CA 92562-7086 . Office (951) 461-1919' Fax (951) 461-7677 I I I I I I I I I I I i I I I I I:m:IINLAND. INC. Geotechnical, Environmental, and Material Testing Consultants January 3, 2007 Project No. 104721-30 Mr. David R. Meade GALLERY DEVELOPMENT 31i618~ 1 Railroad Canyon Road Canyon Lake, California 92587 Subject: Geotechnical Report of Rough Grading, Rear-Yard Extension of Lots 1, 2, 3, and 5 of Tract 23513, City ofTemecula, Riverside County, California This r~ort presents a summary of the observation and testing services provided by LGC Inland, Inc. (LGC), during rough grading operations to develop the subject rear-yard lots in the City of Temecula, Riverside County, California. Conclusions and recommendations pertaining to the suitability of the grading for the proposed residential construction are provided herein. The purpose of grading was to extend the rear-yard areas of Lots 1,2, 3, and 5. Grading on the subject pads began I and was completed during November of 2006. The As-Graded Geotechnical Map, Plate 1, has been modified to reflect "as-built" conditions based on information obtained by our field technician using crude measuring instruments and is for the purpose of locating our field density tests. Our depiction may not aC,curately reflect true configurations. 1.0 REGULATORY COMPLIANCE Removal and re-compaction of low-density surface soils, processing of the exposed bottom surfaces or placement of compacted fill under the purview of this report have been completed under the observation and with selective testing by LGC. Earthwork and grading operations were performed in general accordance with the recommendations presented in the referenced reports (see References) and the grading code of the City of Temecula, California. The completed earthwork has been reviewed and is considered adequate for the construction now planned. On the basis of our observations and field and laboratory testing, the recommendations presented in this report were prepared in conformance with generally accepted professional engineering practices and no further warranty is expressed or implied. 2.0 ENGINEERING GEOLOGY 2.1 Gelleral !I I Geologic conditions exposed during the process of grading were frequently observed and mapped by LGC's geologic/technical staff. I I I 1-- 41531 Date Street. Murrieta. CA 92562-7086' Office (951) 461-1919' Fax (951) 461-7677 I !I i !I I I I I I I I I I I I I I I I I 2.2 Geololdc Units Earth materials within the site included previously placed compacted fill, stockpiled materials, and Rauba Formation. 2.3 Groundwater During over-excavations, no groundwater was encountered. 2.4 Faultinll , No faults were observed during grading operations on the site. 3.0 SUMMARY OF EARTHWORK OBSERVATIONS AND DENSITY TESTING 3.1 I Site Clearinll and Grubbinll Prior to grading, all grasses and weeds were stripped and removed from the site. 3.2 Ground Preoaration , The purpose of this grading operation was to extend the rear-yard areas within the subject lots by , constructing 2: 1 (h:v) fill slopes joining the existing previously engineered slopes. , l:bese slopes consisted of 2: 1 horizontal to vertical (h:v) fill slopes varying up to a maximum height of 25:1: feet. Prior to constructing these additional fill slopes, fill keyways were excavated a minimum of 4 , to 6 feet into the underlying previously placed compacted fill materials or bedrock. The fill keyway bottoms were angled back into the slope and were a minimum of an equipment width and a half wide. As the fills were placed on the existing 2: I (h:v) fill slopes, the slopes were benched a minimum height of 4 feet into competent material or as otherwise recommended by the Geotechnical Consultant. Prior to placing fill, the exposed bottom surfaces were scarified to depths of 6 to 8 inches, watered or , air-dried as necessary to achieve at or slightly above optimum moisture content and then re-compacted in-place to a minimum relative compaction of 90 percent. 3.3 I Disoosal of Oversize Rock I Oversize rock (rock generally greater than I-foot in maximum dimension) was not encountered during I the removal operations. 17 Project No. 104721-30 Page 2 January 3.2007 I I I II I , :I I I I I I I I I I I I I I I 3.4 Fill Placement and Testinll Fill materials consist of stockpiled soils generated from the previous rough grading operations. All fills were placed in lifts restricted to approximately 6 to 8 inches in maximum thickness, watered or air-dried as necessary to achieve near optimum moisture conditions, then compacted in-place to a minimum relative compaction of 90 percent by rolling with a bulldozer, loaded scrapers, or loaded water truck. The maximum vertical depth of fill placed within the subject pads as a result of grading is approximately 15 feet. Field density and moisture content tests were performed in accordance with ASTM Test Methods D2922 and D3017 (nuclear gauge). Test results are presented on Table II (attached) and test locations are shown on the enclosed As - Graded Geotechnical Map (Figure 1). Field density tests were taken at vertical intervals of approximately I to 2 feet and the compacted fills were tested at the time of placement to verify that the specified moisture content and minimum required relative compaction of 90 percent had been achieved. At least one in-place density test was taken for each 1,000 cubic yards of fill placed and/or for each 2 feet in vertical height of compacted fill. The actual number of tests taken per day varied with the project conditions, such as the number of eartbrnovers (scrapers) and availability of support equipment. When field density tests produced results less than the required minimum relative compaction of 90 percent, the approximate limits of the substandard fill were established. The substandard area was then reworked, moisture conditioned, re- compacted, and retested until the minimum relative density was achieved. Visual classification of earth materials in the field was the basis for determining which maximum dry density value, summarized in Appendix B, was applicable for a given density test. One-point checks were periodically performed to supplement visual classification. 4.0 LABORATORY TESTING 4.1 Maximum Drv Densitv Maximum dry density and optimum moisture content for the major soil types observed during grading were determined in our laboratory in accordance with ASTM Test Method DI557-00. Pertinent test values are summarized in Appendix B. 5.0 POST GRADING CONSIDERATIONS 5.1 Landscaoinll and Maintenance of Graded Slooes Unless long term mitigation measures are taken, the slopes may be subject to a low to moderate degree of surficial erosion or degradation during periods of heavy rainfall. Therefore, it is recommended that fill slopes be landscaped with a deep-rooted, drought-resistant, woody plant species. To provide temporary slope protection while the woody materials mature, the slopes should be planted with an herbaceous plant species that will mature in one season or provided with some other protection, such as jute matting or polymer covering. The temporary protection should be maintained until the woody material has become fully mature. A landscape architect should be consulted to determine the most suitable plant materials and irrigation requirements. ~ Project No. 104721-30 Page 3 January 3.2007 I I I I I To mitigate future surficial erosion and slumping, a permanent slope-maintenance program should be initiated. Proper slope maintenance must include regular care of drainage- and erosion-control provisions, rodent control, prompt repair of leaking irrigation systems and replacement of dying or dead plant materials. The irrigation system should be designed and maintained to provide constant moisture content in the soils. Over-watering, as well as over-drying, of the soils can lead to surficial erosion and/or slope deterioration. lbe owners should be advised of the potential problems that can develop when drainage on their pads and adjacent slopes is altered in any way. Drainage can be adversely altered due to the placement of fill and construction of garden walls, retaining walls, walkways, patios, swimming pools and planters. 5.2 Bad Drainalle II i !I I II I I I I I I I I I I Drainage on the pads should be designed to carry surface water away from all graded slopes and structures. Pad drainage should be designed for a minimum gradient as requires by the UBC with drainage directed to the adjacent drainage facilities or other location approved by the building official. Ground adjacent to foundations shall be graded so that it is sloped away from the building at least 12:1 (h:v) (4.8') for a minimum distance of 6 feet, or another alternative approved way shall be found to divert water from the foundation. Positive drainage away from the structures and slopes should be provided on the lots by means of earth swales, sloped concrete flatwork and area drains. 6.0 LIMITATIONS Our services were performed using the degree of care and skill ordinarily exercised, under similar circumstances, by reputable engineers and geologists practicing in this or similar localities. No other warranty, expressed or implied, is made as to the conclusions and professional advice included in this report. This report is issued with the understanding that it is the responsibility of the owner, or of his /her representative, to ensure that the information and recommendations contained herein are brought to the attention of the architect and/or project engineer and incorporated into the plans, and the necessary steps are taken to see that the contractor and/or subcontractor properly implements the recommendations in the field. The contractor and/or: subcontractor should notify the owner if they consider any of the recommendations presented herein to be unsafe. The findings of this report are valid as of the present date. However, changes in the conditions of a property can and do occur with the passage of time, whether they be due to natural processes or the works of man on this or adjacentproperties. 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 modification, and should not be relied upon after a period of 3 years. '5 Project No. 104721-30 Page 4 January 3, 2007 I I I 'I I I I I I I I I I I I I I I I TIns opportunity to be of service is sincerely appreciated. Please call if you have any questions pertaining to this report. Respectfully submitted, LGC INLAND, INC. ~~~~ Chad E.Welke, CEG 2378, PE 63712 Associate Geologist/Engineer GEU/CEW /SER/ko/kg Attachments: Distribution: (6) Addressee l, ProjectlVo, 104721-30 Page 5 January 3,2007 I I I I I II I I I I II , ,I I I I I I I I APPENDIX A REFERENCES ,Blake, T.F., 2000, "FRISKSP, Version 4.0, A Computer Program for the Probabilistic Estimation of Peak Acceleration and uniform Hazard Spectra Using 3-D Faults as Earthquake Sources." , 1998/1998, "UBCSEIS, Version 1.30, A Computer Program for the Estimation of Uniform Building Code Coefficients Using 3-D Fault Sources. International Conference of Building Officials, 1997, Uniform Building Code, Structural Engineering Design Provisions. Leighton and Associates, 1999, Preliminary Geotechnical Evaluation, Grading Plan Review, Tract 23513 and Adjacent Parcel 4, P.N. 11900246-003, dated July 19. LGC Inland, Inc., 2005, Geotechnical Report of Rough Grading, Tentative Tracts 23513 (lllots) and 29466 (4 lots), CityofTemecula, Riverside County, California, PNI04721-30, dated August 19. (0