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Home My WebLink AboutPD 2021-0040; 786 PALM AVENUE; RESPONSE TO COMMENTS AND PLAN REVIEW PROPOSED RESIDENCE WITH ADU; 2022-05-05 GEOTECHNICAL | ENVIRONMENTAL | MATERIALS May 5, 2022 Project No. 3653-SD AB 3 C/O P&E Coast Construction 2834 La Mirada Drive, Suite E Vista, California 92081 Subject: Response to Comments and Plan Review Proposed Residence with ADU 786 Palm Avenue APN 214-39-010 & 11 Carlsbad, California 92008 This letter is prepared to respond to comments in in “Third-Party Geotechnical Review (First), 785 Palm Avenue, Carlsbad, California, PD202 l-0040/GR202 l-0040” by Hetherington Engineering, Inc. (HEI) dated October 20, 2021 (copy attached). The comments by HEI are indicated below numbered as in the review, our response follows the HEI comment. 1) Due to the age of the reports, the Consultant should update References 1 and 2 to comply with requirements of the 2019 California Building Code, ASCE 7-16, and City of Carlsbad requirements. Subsurface exploration soil/bedrock sampling and laboratory testing should be presented to justify the grading and foundation recommendations. a. Updated references are attached. Reference 1 has been updated, the 2019 California Building Code which was accidentally omitted from the Reference it was cited in the text. Logs of the borings are attached locations were indicated on Figure 2 in GeoTek’s reports. The locations are also presented on Figure 4. 2) The Consultant should review the project grading plan (Reference 3) and foundation plans, provide any additional geotechnical analyses/recommendations considered necessary, and confirm that the plans have been prepared in accordance with the geotechnical recommendations. a. We reviewed plans for the project including the “Grading Plans” by bHA, Inc. and applicable portions of the Structural Plans prepared by Nader's Design Consulting, Inc. as indicated on the enclosed reference list. Provided that recommendations for site grading are followed both the Grading and Structural AB3 May 4, 2022 786 Palm Avenue, Carlsbad PN 3653-SD Response to Comments Page 2 plans are in accordance with the recommendations contained in Reference 8, the plans are considered to incorporate GeoTek’s recommendations. 3) The Consultant should provide an updated geotechnical map utilizing the current grading plan for the project to clearly show (at minimum): a) existing site topography, b) proposed structures/improvements, c) proposed finished grades, d) geologic conditions, e) locations of the subsurface exploration, f) temporary construction slopes, g) remedial grading, etc. a. A portion of the Grading Plan is used as the base plan for the Figure 4 Remedial Plan. (The figure is numbered sequentially with those in prior reports). The requested items are indicated on the plan. The only temporary construction slopes would be as the result of remedial grading. Specifically, expected removals are 3 to 3.5 feet from finished or existing grade in the foundation areas. Ideally these would extend at least 5 Feet beyond the foundation perimeter grade considering the foundation setback from property lines this should not impact adjacent properties with the possible exception of approximately 30 feet along the north wall of the structure on Lot 10. In that area a one-foot setback from the property line should be maintained with a 1:1 slope down. Once removals are observed and assessed to be sufficiently deep then the slope may be benched to complete the removals. The benching should be restricted to 10-foot horizontal slots and the fill in this area backfilled to within 2 feet of existing grade in the course of one day. The only other anticipated temporary slopes would be for utilities which were addressed in the original reports. 4) The Consultant should address impacts of the proposed grading and construction on adjacent properties and improvements. a. No significant impact from geotechnical conditions is expected on adjacent properties. 5) The Consultant should provide the site Seismic Design Category and Risk Category. a. Based on CBC Table 1604.5 Risk Category of Buildings and Other Structures the Risk Category is “II”. Based on CBC Table 1613.2.5(1) Seismic Design Category Based on Short-Period (0.2 second) Response Acceleration and that SDS exceeds 0.5g the Seismic Design Category is “D”. AB3 May 4, 2022 786 Palm Avenue, Carlsbad PN 3653-SD Response to Comments Page 3 6) Foundation and slab design criteria for soils should be consistent with Section 1808.6 of the 2019 California Building Code. The Consultant should provide expansion index test results and update foundation recommendations, as necessary. a. In response a composite sample of soil from the upper one foot at the locations of HA-1 and HA-2 was obtained. Attached is the result of an expansion index test indicating an E.I. of zero and as such are not considered to be expansive per CBC section 1803.5.3 Expansive soil. No change in prior recommendation is needed. 7) The Consultant should specify the sulfate exposure category (ACI 3I8) based on soluble sulfate testing and provide recommendations for sulfate resistant concrete, if necessary, or default to a severe exposure category, if testing is not available. a. Attached are the results on a sulfate test on the above describe sample, indicating of 0.0087 which SO and does not require a sulfate resistant mix design. The opportunity to be of service is sincerely appreciated. If you should have any questions, please do not hesitate to call our office. Respectfully Submitted, GeoTek, Inc. Timothy E. Metcalfe, CEG 1142 Principal Geologist Chris E. Lillback, GE 35007 Senior Project Engineer Reference: 1. ASCE/SEI 7-16, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, published by The American Society of Civil Engineers, 2017 2. ASTM, Test methods D-420 to D-5876, ASTM test method D-5877 to latest. (online access at https://secure.astm.org) 3. California Code of Regulations, Title 24, 2019 “California Residential Building Code,” 3 volumes. 4. California Code of Regulations, Title 24, 2019 “California Building Code,” Part 2, Volume 1 of 2 volumes. 5. California Division of Mines and Geology (CDMG), 2008, “Guidelines for Evaluating and Mitigating Seismic Hazards in California,” Special Publication 117A 6. GeoTek, Inc., In-house proprietary information. 7. Seismic Design Values for Buildings (http://seismic.org). 8. Geologic Map of the Oceanside 30' X 60' Quadrangle, California, Compiled by Michael P. Kennedy and Siang S. Tan, 2005 Digital Preparation by Kelly R. Bovard1, Rachel M. Alvarez1and Michael J. Watson1 U.S. Geological Survey, Department of Earth Sciences, University of California, Riverside 9. “Limited Geotechnical Evaluation, Proposed Residence with ADU, 786 Palm Avenue APN 214-39-011, Carlsbad, California 92008” by GeoTek, Inc. dated August 14, 2020 (PN 3653-SD) 10. “Grading Plans for: 786 Palm Avenue, Carlsbad, California” by bHA Inc. print date September 13, 2021 11. Structural Plans: Single Family Home, ADU, Casita & Garage 786 Palm Avenue, Carlsbad, CA specifically Foundation Plan Unit 10 Sheet S1, Foundation Plan Unit 11 also Sheet S1 Structural Details Sheet SD1, by Nader's Design Consulting, Inc dated November 23, 2021 12. Third-Party Geotechnical Review (First), 785 Palm Avenue. Carlsbad, California, PD202 l-0040/GR202 l-0040” by Hetherington Engineering, Inc. dated October 20, 2021