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HomeMy WebLinkAbout20200909113038027 (13)a fliamfictofi, eo ehnie l ngineerin;g, Inc. March 19, 1997 APPRaVEx Mr. Leonel Paz Architect/General Contractor 3448 Lee Street Los Angeles, CA 90023 Re: Geotechnical Review of Partial Grading and Retaining Wall Plan for Lot 8, Tract 47851;'Crystal Ridge Estates, Diamond Bar, California HGEI Project No. 91-02-0109a-08 References: see Attached List Dear Mr. Paz: In response to your request and authorization on March 10, 1997, we have re- viewed the referencedgrading and retaining,wall plan for Lot 8 of Tract 47851. The referenced plan and details were reviewed from a geotechnical standpoint for conformance with our recommendations only. These plans and details were not reviewed as to the accuracy of dimensions, measurements, calculations or any non-geotechnical portion of the design. Findings Based upon our review it appears that the referenced plan and details are in general conformance with our previous recommendations. During this review the following items were noted: 1. No significant changes to the building pad elevations are 'currently planned. The homeowner should be informed that future grading to alter the pad and/or slopes should not be performed without review by a geotechnical consultant familiar with rough grading of the tract. it should be noted that the rear slope consists of a shear key constructed during rough grading for stability of the building pad. In addition, the homeowner should be informed of the importance of slope landscaping, maintenance Batavia Business Center, 1938 North Batavia Street, Suite N, Orange, CA 92865 (714) 637-3093 (800) 924-7645 FAX (714) 637-3096 Mr. Leonel Paz HGEI Project No. 91-02-0109a-08 March 19, 1997 Page 2 and erosion control and should be provided with the guidelines that were appended to the referenced rough grading report (Appendix C). t 2. Two retaining walls are proposed: One is to be approximately five feet high and will be cut into the 2:1 (H:V) ascending fill slope along the north side property line; the other will vary up to a maximum six feet in height and will be constructed on the 2:1 H:V descending fill,slopee located at the eastp edge of the pad area. The descending slope constitutes part of the shear key described in paragraph 1. Retaining Wall Recommendations The proposed cantilever -type retaining walls may be designed using an active equivalent fluid density of 30 pounds per cubic foot for level backfill. Footings should be bottomed at a minimum depth of 18 inches below the lowest adjacent grade in which case an allowable soil bearing pressure of 2,000 pounds per square foot may be used to design the footings. The outside bottom edge of the footing of the 6±-ft-high retaining wall should be set back horizontally at least five feet from the face of the descending slope. A friction coefficient of 0.4 between concrete and soil and a passive bearing pressure of 250 pounds per square foot per foot of depth are recommended for checking sliding resistance. The walls should be provided with either weep holes or subdrains to provide drainage of the backfill in order to prevent hydrostatic pressure on the wall. Backfill placed within 12 inches of the walls and to within 18 inches of finished grade should consist of material exhibiting a sand equivalent of at least 30. The remainder of the backfills should consist of site material which wili. impede surface water infiltration. Backfills must be adequately compacted to preclude the occurrence of objec- tionable post -construction subsidence. In general, a minimum relative compac- tion of 90 percent will be required for geotechnical approval of backfills. Backfill for the 6-foot-high wall should be benched, into existing fill soil with horizontal benches at least, 3 feet.wide. Mr. Leonel Paz HGEI Project No. 91-02-0109a-08 March 19, 1997 Page 3 Caution must'be exercised during placement and compaction of backfill',materi- als to avoid temporarily overstressing the walls. Surface Drainage Surface drainage should be established as, shown on the partial grading and retainingwall plan and/or in accordance with the Uniform Building Code during fine grading and landscaping of the wall areas. Such drainage is important for wall stability and protection' of any adjacent concrete flat work. Accordingly, drainage should be properly maintained by the homeowner and should not be altered without professional advice. limitations/ Closure The recommendations and opinions expressed in this report reflect our best esti- mate of project conditions and requirements based on geotechnical data previ- ously established. Variations in subsurface conditions which could have an influ- ence on footing and retaining wall performance may occur in unexplored areas, Any unanticipated conditions encountered in the course of construction should be brought ° to, the attention of the geotechnical engineer for evaluation prior to proceeding with,the work. Harrington Geotechnical Engineering, Inc. has attempted to conduct the service reported herein in a manner consistent with that level of care and skill ordinarily exercised by members of the profession currently practicing in the same locality and under similar, conditions as this project; No other representation, express or implied, an no warranty or guarantee is included or intended by issuance of this report. This report has been' prepared in accordance with generally accepted geotechnica. l engineering practice common to the local area for exclusive use by Mr. Leonel Paz and/or his authorized representative for design/construction of the' proposed retaining walls at the subject site. This report shall not be used by other parties or for other projects without written consent of Harrington Geotechnical Engineering, Inc. This report will be valid for a period`of one year from date of issue and will then be subject to review and revision. Mr. Leonel Paz HGEI Project No. 91-02-0109a-08 March 19, 1997 GEOTECHNICAL REVIEW SHEET LEIGHTON AND ASSOCIATES, INC. FOR CITY OF DIAMOND BAR DEPARTMENT OF ENGINEERING 2910164-085 Tract(s) 47851, Lot 8 Date April 30, 1997 Parent Tract Location/Owner "The Country"/ Site Address 2838 Bentley Way Geologist Developer Leonel Paz Soils Engineer Harrington Geotechnical Engineer/Arch. Grading P.C. No. Geologist. Report(s) Dated X Soils Reports) Dated March 19, 1997 Geology and Soils Report(s) Dated Other Previous Submittals Dated ACTION: X Plan/Rgport is geotechnically approved Plan/report not approved for reasons below Plan/Report is geotechnically approved Submit Plan/Report for recheck. Include a copy of subject to conditions below. this review. REVIEW COMMENTS: Reviewed bYam.. Date April 30, 1997 David C. Smith Eq 0 M" LEIGHTON ANDASSOCIA FES, INC. Mr. Leonel Paz HGEI Project No. 91-02-0109a-08 March 19, 1997 Page 2 and erosion control and should be provided with the guidelines that were appended to the referenced rough grading report (Appendix C). 2. Two retaining walls are proposed: ,One is to be approximately five feet high and will be cut into the 2:1' (H:V) ascending fill slope along the north side property line; the other will vary up to a maximum six feet in height and will be constructed on the 2:1 (H:V) descending fill slope located at the east edge of the pad area. The descending slope constitutes part of the shear key described in paragraph 1. Retaining Wall Recommendations The proposed cantilever -type retaining' walls may be designed using an active equivalent fluid density of 30 pounds per cubic foot for level backfill. Footings should be bottomed at a minimum depth of 18 inches below the lowest adjacent grade in which case an allowable soil bearing pressure of 2,000 pounds per square foot may be used to design the footings. The outside bottom edge of the, footing of the b±-ft-high retaining wall should be set back horizontally; at least five feet from the face of the descending slope. A friction coefficient of 0.4 between concrete and soil and a passive bearing pressure of 250 pounds per square foot per foot of depth are recommended for checking sliding resistance. The walls should be provided with either weep holes or subdrains to provide drainage of the backfill in order to prevent hydrostatic pressure on the wall. Backfill placed within 12 inches of the walls and to within 18 inches of `finished grade should consist of material exhibiting a sand equivalent of at least 30. The remainder of the backfills should consist of site material which will impede surface water infiltration. Backfills must be adequately compacted to preclude the occurrence of objec- tionable post -construction subsidence. In general, a minimum relative compac- tion of 90 percent will be required for geotechnical approval of backfills. Backfill for the 6-foot-high wall should be benched into 'existing fill `soil with horizontal benches at least 3 feet wide. Mr. Leonel Paz HGEI Project No. 91-02-0109a-08 March 19, 1997 Page 3 Caution must be exercised during placement and compaction of backfili materi- als to avoid temporarily overstressing the walls. Surface Drainage Surface drainage should be established as shown on the partial grading and retaining wall; plan and/or in accordance with the Uniform Building Code during fine grading and landscaping of the wall areas. Such drainage is important for wall stability `and protection of any adjacent concrete flat work.' Accordingly, drainage should be properly maintained by the homeowner and should not be altered without professional advice. Limitation s/Closure The recommendations and opinions expressed in this report reflect our best esti- mate of project conditions and requirements based on geotechnical data previ- ously established. Variations in subsurface conditions which could have an influ- ence on footing and retaining wall performance may occur in unexplored areas. Any unanticipated conditions encountered in the course of construction should be brought to the attention of the geotechnical engineer for evaluation prior to proceeding with the work. Harrington Geotechnical Engineering, Inc. has, attempted to conduct the service reported herein in a manner consistent with that level of care and skill ordinarily exercised by'member's of the profession currently practicing in the same locality and under similar conditions as this project. No other representation, express or implied, an no warranty or, guarantee is, included or intended by issuance of this report. This report has been prepared in accordance with generally accepted geotechnical engineering practice common to the local area for exclusive use by Mr. Leone[ Paz and/or his authorized representative for design/construction of the proposed retaining walls at the subject site. This report shall not be used by other parties or for other projects without written consent of Harrington Geotechnical Engineering;, Inc. This report will be valid for a period of one year from date of issue and will then be subject to review and revision. 4 Mr. Leonel Paz HGEI Project No. 91-02-0109a-08 March 19, 1997