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Home My WebLink AboutCT 2018-0004; THE SEAGLASS; Technical Memorandum Geotechnical Review Comments; 2019-11-25Geotechnical CCCC Geologic CCCC Coastal CCCC Environmental 5741 Palmer Way C Carlsbad, California 92010 C (760) 438-3155 C FAX (760) 931-0915 C www.geosoilsinc.com TECHNICAL M E M O R A N D U M Date: November 25, 2019 W.O. 7544-A-SC To: 2646 Sea Glass, LLC c/o Prophet Solutions 5845 Avenida Encinias, Suite 138 Carlsbad, California 92008 Attention: Mr. Rodney A. Boone From: Robert G. Crisman, CEG 1934 David W. Skelly, RCE 47857 Exp. 3-31-20 Subject: Response to Third Party Geotechnical Review Comments, The “Sea Glass” Project, 2646 State Street, Carlsbad, California In accordance with your request, GeoSoils, Inc. (GSI), has reviewed the third party geotechnical review prepared by Hetherington Engineering Company (HEI, 2019), with respect to the Sea Glass project in the City of Carlsbad, Ca. Based on our review, the following responses are provided. For ease of review, the specific comment from Reference is presented below, with the appropriate GSI response. Review Comment No. 1: “The consultant should review the project grading and foundation plans, provide any additional geotechnical analysis/recommendations considered necessary, and confirm that the plans have been prepared in accordance with the geotechnical recommendations (second request).” Response to Comment No. 1: Acknowledged. A review of the grading and foundation plans, prepared by Pasco, Laret, Suiter & Associates (PLSA, 2019a) and Patterson Engineering (PE, 2019a, 2019b), respectively, was performed by GSI (2019b) in response to previous plan check comments from another agency (Esgil, 2019). Based on the review, and our review performed in preparation of this memorandum, it is concluded that the foundation plans (PE, 2019a), structural calculations (PE, 2019b), and grading plans (PLSA, 2019a) were prepared in accordance with the intent of the geotechnical reports (GSI, 2018a, 2018b, 2015), and were satisfactory from a geotechnical viewpoint. A review of the improvement plans (PLS, 2019b) was also performed, with the plans also found to be satisfactory, and in accordance GeoSoils, Inc. 2646 SeaGlass, LLC W.O. 7544-A-SC 2646 State Street, Carlsbad November 25, 2019 File:e:\wp9\7500\7544a.rtt Page 2 with the intent of the geotechnical reports. Review Comment No. 2: “The consultant should address impacts to adjacent property and improvements as a result of grading and construction. (second request).” Response to Comment No. 2 Acknowledged. Per GSI (2018b): “GSI anticipates that due to the nature of the subsurface earth materials and the location of adjacent developments/improvements, the completion of remedial grading about the perimeter of the site will likely require slot cuts to complete the installation and construction.” “Remedial grading may utilize alternating (“A’, “B,” and “C”) slot excavations adjacent to any settlement sensitive improvements (walls, building, etc.) to remain about the perimeter of the site. A maximum slot cut width of 8 feet may be considered, on a preliminary basis.” Alternatively, where feasible, remedial earthwork excavations (i.e., removals) should remain above a 1:1 projection (h:v) down and away from the intersection of the ground surface at the property line. Provided that the recommendations presented in the referenced reports (see Appendix) are incorporated into the design and construction of the structure(s), the proposed grading and site construction should not have any adverse impacts on the surrounding properties/improvements. Review Comment No. 3 “The consultant should provide minimum reinforcement recommendations for conventional foundations. (second request).” Response to Comment No. 3: GSI (2018b, 2015) indicates that “reinforcement should be designed in accordance with local codes and structural considerations.” Reinforcement of conventional, continuous strip foundations should minimally consist of four (4) No. 4 reinforcing bars, two (2) top, and two (2) bottom. It should be noted that the plan foundation system uses a mat slab design (Patterson Engineering, Inc. 2019a/b), with respect to the expansive soil conditions identified onsite. GeoSoils, Inc. 2646 SeaGlass, LLC W.O. 7544-A-SC 2646 State Street, Carlsbad November 25, 2019 File:e:\wp9\7500\7544a.rtt Page 3 Review Comment No. 4: “The consultant should provide recommendations for sulfate resistant concrete based on the soluble sulfate test results consistent with ACI 318, Table 4.3.1 (Second Request).” Response to Comment No. 4: As indicated in GSI (2018b): “Corrosion evaluations prepared in preparation of GSI (2015) indicate that the tested samples of the onsite soils are moderately alkaline with respect to soil acidity/alkalinity; are corrosive to exposed, buried metals when saturated; present negligible, to moderate sulfate exposure to concrete (per Table 19.3.1.1 of ACI 318R-14); and have low chloride content. It should be noted that GSI does not consult in the field of corrosion engineering. Thus, the client, project architect, and project structural engineer should agree on the level of corrosion protection required for the project and seek consultation from a qualified corrosion consultant as warranted, especially in light of the site’s proximity to the Pacific Ocean, which is a corrosive environment. It should be noted that sulfate levels indicate a sulfate exposure Class S1, and a moderate corrosion exposure class of C1 (concrete will be exposed to moisture), per Tables 19.3.1.1 and 19.3.2.1 of ACI 318R-14 (ACI, 2014).” Closure Unless specifically superceded herein, the conclusions and recommendations presented in the referenced reports by GSI (see Appendex) remain valid and applicable. The conclusions and recommendations presented herein are professional opinions. These opinions have been derived in accordance with current standards of practice, and no warranty is express or implied. Standards of practice are subject to change with time. GSI assumes no responsibility or liability for work or testing performed by others, or their inaction, or work performed when GSI is not requested to be onsite, to evaluate if our recommendations have been properly implemented. Use of this report constitutes an agreement and consent by the user to all the limitations outlined above, notwithstanding any other agreements that may be in place. In addition, this report may be subject to review by the controlling authorities. Attachment: Reference Appendix GeoSoils, Inc. 2646 SeaGlass, LLC W.O. 7544-A-SC 2646 State Street, Carlsbad November 25, 2019 File:e:\wp9\7500\7544a.rtt Page 4 REFERENCE APPENDIX Hetherington Engineering, Inc, 2019, Third party geotechnical review (second), proposed four-level residential structure, 2646 State Street, Carlsbad, California,” dated September 9, 2019, Project ID GR2019-0025, Project No. 8932.1, Log No. 20647, dated September 9. Esgil Corporation, 2019, 8 Residential Town homes with individual garage with elevator for 7 Units for 2646 Sea Glass LLC, Plan Chk# PC2019-0046, dated June 24. GeoSoils, Inc., 2019a, Second geotechnical plan review and response to City plan review comments, “Sea Glass” project, 2646 State Street, Carlsbad, California, W.O. 7544- A-SC, dated August 5. _____, 2019b, Supplement to the geotechnical plan review and response to City plan review comments, “Sea Glass” project, 2646 State Street, Carlsbad, California, W.O. 7544-A-SC, dated August 1, 2019, by GeoSoils, Inc. _____, 2018a, Review and comment regarding the planned pervious paver driveway, “Sea Glass” project, 2646 State Street, Carlsbad, California, W.O. 7544-A-SC, dated December 3. _____, 2018b, Geotechnical update for “The Sea Glass,” 2646 State Street, Carlsbad, California 92008, W.O. 7452-A-SC, Dated May 31. _____, 2015, Geotechnical evaluation, ‘The Wave,’ 2646 State Street, Carlsbad, San Diego County, California, W.O. 6935-A-SC, dated November 3. Patterson Engineering, Inc., 2019a, Structural plans, notes, and details for: The Sea Glass, new construction 2646 State Street, Carlsbad, Ca. 92008, AN 203-101-20-00, SEA Job No. 1713, dated August 5. _____, 2019b, Structural calculation package, plan check response calculation, State Street condominiums, 2646 State Street, Carlsbad, Ca. 92008, Project No. 17090087, Dated July 31. Pasco Laret Suiter, Associates, 2019a, Grading Plans for: The SeaGlass, P.N. CT2018- 0004, DWG 519-2, J.N. 3078, Plot dated October 23. _____, 2019b, Improvement plans for: The SeaGlass, 2646 State St., Project No. CT2018- 0004, DWG 519-2, J.N. 3078, Plot dated October 23.