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HomeMy WebLinkAbout2818_Bentley Wygain ton 1181fieerffl& Inc. October 20, 1995 Mr. Bernist Mazur DIAMOND BAR EAST PARTNERS 3480 Torrance Boulevard, Suite 300 Torrance, CA 90503 SUBJECT: Geotechnical Review of Precise Grading Plan for 2818 Bentley Way, Lot 4, Tract 47851, Crystal Ridge Estates, Diamond Bar, California HGEI Project No. 91-02-0109A-04 REFERENCES: 1) "Geotechnical Report of Rough Grading for Lots 1-17 and 20-48, Vesting Tentative Tract 47851, Diamond Bar, California," Dated October 11, 1994, Prepared by HGEI, Project No. 91-02-0109A. 2) Rough Grading Plan, Sheets 1 thru 7, Tract 47851, Prepared by Hunsaker & Associates, Inc. 3) Precise Grading Plan for the Subject Lot, Dated September 14, 1995, Prepared by Pfeiler & Associates, Engineers. 4) Standard Recommendations for Precise Grading, Slope Maintenance and Foundation Design for the Subject Tract, Dated September 20, 1995, by HGEI, Project No. 91-02-0109A. Dear Mr. Mazur: In response to a request from R. Gould & Associates, Inc., we have reviewed the referenced precise grading plan for Lot 4 of Tract 47851. The referenced plan was reviewed from a geotechnical standpoint for conformance with our recommendations only. The plan was not reviewed as to the accuracy of dimensions, measurements, calculations or any non-geotechnical portion of the design. Based upon our review it appears that the referenced plan is in conformance with our previous recommendations. During this review the following items were noted: 1. Comparison of the pad elevation shown on the precise grading plan with the as - graded elevation shown on the rough grading plan indicates that no significant grading within the building limits is planned. Maximum depth of fill and cut is on the order of foot. I Batavia Business Center, 1938 North Batavia Street, Suite N, Orange, CA 92665 (714) 637-3093 - (800) 924-7645 - FAX (714) 637-3096 DIAMOND BAR EAST PARTNERS Project No. 91-02-0109A-04 October 20, 1995 Page 2 2. The precise grading plan indicates that outside the building limits the grade will be lowered up to four feet for control of surface drainage and construction of the driveway. 3. No significant changes to the on -site rear slope or the southerly adjacent sideyard slope are planned. 4. In order to provide clearance between the proposed structure and the northerly sideyard slope a retaining wall is proposed along the lower portion of the slope. This wall will have a maximum height of approximately nine feet. The minimum setback for the structure from the retaining wall is eight feet. This distance exceeds the standard setback of H/2 as specified by the Uniform Building Code. 5. A second retaining wall is indicated along the lower portion of the northerly sideyard slope for a future at -grade tennis court. 6. Retaining walls proposed along the northerly side of the residence and for the tennis court may be designed using the soil parameters and recommendations presented in the referenced geotechnical report of rough grading and an equivalent active earth pressure of 45 pounds per square foot per foot of depth for cantilever walls retaining sloped backfill with an inclination of 2:1 (H:V). 7. The proposed residence location is outside the foundation setback line shown on Plate A-1 of the geotechnical report of rough grading (Ref. 3). As a result, special deepened foundations will not be necessary on this lot. 8. The homeowner should be informed that future grading to alter the slopes should not be performed without review by a geotechnical consultant familiar with rough grading of the tract. In addition, the homeowner should be informed of the importance of slope landscaping, maintenance and erosion control and should be provided with the guidelines pertaining to slope maintenance that were part of Reference No. 4. 9. The shear key along the top of the rear slope was constructed as part of the tract rough grading. Thus, the call out of " Proposed Shear Key" should be changed to Approximate Shear Key Location" or removed from the precise grading plan. 10. Subdrains/backdrains should be provided behind the proposed retaining walls. A drainage system should be shown on the retaining wall details or a .note added to the wall details referencing the subdrain shown in Section B-B'. We have revised as necessary, stamped and signed three copies of the precise grading plan and are returning them to Richard Gould of JCC Homes, as requested. DIAMOND BAR EAST PARTNERS Project No. 91-02-0109A-04 October 20, 1995 Page 3 We trust that this letter/report is adequate for your current needs. If you have any questions or require further assistance, please call. Very truly yours, HARRINGTON GEOTECHNIC J. Stanley "Schweitz e"'--r', P" Senior Geotechnical E 61C' Distribution: Addressee R. Gould & C:WOCS\DBARU'LANRVVVXLOT4GRDG.RVW AL ENGINEERING, INC. 3)