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HomeMy WebLinkAboutCDP 2019-0002; HILLSIDE DRIVE RESIDENTIAL; RESPONSE TO CITY OF CARLSBAD THIRD-PARTY GEOTECHNICAL REVIEW (SECOND); 2021-04-13 13 April 2021 Mr. Jessie Smith Job No. 18-11842 447 Bougher Road San Marcos, CA 92068 Subject: Response to City of Carlsbad Third-Party Geotechnical Review(second) Smith Residential Lot 4246 Hillside Drive Carlsbad, California References: Hetherington Engineering, Inc., 2020, Third-Party Geotechnical Review (second), Proposed Single-Family Residence 4246 Hillside Drive Carlsbad California, Project No 9142.1, Log No. 21259 dated January 7 2021. Geotechnical Exploration Inc., 2020, Update Report of Preliminary Geotechnical Investigation, Smith Residential 4246 Hillside Drive Carlsbad, California. Project No. 18-11842, dated November 13, 2020. Response to City of Carlsbad, Third Party Geotechnical Review, Smith Residential Lot, 4246 Hillside Drive, Carlsbad, California, by Geotechnical Exploration, Inc., dated November 13, 2020. Additional references are listed in Appendix A. Dear Mr. Smith: In accordance with the request of Mr. Dan Valdes with Coffey Engineering, and as required by the City of Carlsbad Third Party Reviewer, Geotechnical Exploration, Inc. herein responds to the reviewer comments in a memo with completion date January 7, 2021 (referenced above), with respect to the planned residential project at the subject property. For clarity purposes, we include the comment and our response to it. Smith Residential Lot Job No. 18-11842 Carlsbad, California Page 2 Comment No. 1: The Consultant should provide a statement that the foundation and slab recommendations (expansive soils) are consistent with the requirements of Section 1808.6.2019 California Building Code or revise accordingly (second request). Response: The California Building Code Section 1808.6.2019 gives several options regarding the recommendations for foundations and slabs on-grade for expansive soil conditions. Among them are designing the slabs and foundations for uplift pressures and anticipated soil movement, excavating soil and replacing with lower expansive soils, etc. Per Section 1808.6.4.2019, the expansive soil active zone may be stabilized by pre-saturation or treatment during grading. It is our opinion that the foundation and slab recommendations provided by our firm in our Updated Geotechnical Report dated November 13, 2020, are consistent with the requirements of Section 1898.6.2019. We have recommended that low expansive soils be compacted to within 2 percent of optimum, and if medium or highly expansive soils are encountered during grading, they should be compacted with a moisture content of at least 5 percent over optimum. Furthermore, the foundation and slab on-grade minimum dimensions recommended by our firm are appropriate for the encountered soils at the site. Based on our exploratory work, we have visually classified the on- site soils to be low expansive, with an expansion index no higher than 50. The foundation and slab recommendations presented in our November 13, 2020, report are applicable for such soils. This opportunity to be of service is sincerely appreciated. Should you have any questions concerning the following report, please do not hesitate to contact us. Reference to our Job No. 18-11842 will expedite a response to your inquiries. Respectfully submitted, GEOTECHNICAL EXPLORATION, INC. _______________________________ ______________________________ Jaime A. Cerros, P.E. Hector G. Estrella, C.E.G. Senior Geotechnical Engineer Engineering Geologist R.C.E. 34422/G.E. 2007 P.G. 9019/C.E.G. 2656 APPENDIX A ADDITIONAL REFERENCES 1. Preliminary Geotechnical Investigation, Smith Residential Lot, South of 4240 Hillside Drive, Carlsbad, California, by Geotechnical Exploration, Inc., dated April 9, 2018. 2. Grading Plans For: Smith Residence, 4246 Hillside Drive, Carlsbad, CA GR20200022, CDP2019-002, by Bendlund Engineering, undated (Sheets 1 through 3). 3. Third Party Geotechnical Review (First), Proposed Single Family Residence, 4246 Hillside Drive, Carlsbad, California, Project ID: CDP2019-0002 by Hetherington Engineering, Inc. dated June 19, 2020. 4. Grading Plans For: Smith Residence, GR2018-0022, CDP2019-002, by Bendlund Engineering, undated (Sheets 1 through 5).