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Home My WebLink AboutCT 16-05; QUARRY CREEK; RESPONSE TO THIRD PARTY REVIEW COMMENTS; 2020-06-05GEOCON INCORPORATED GEOTECHNICAL • ENVIRONMENTAL U MATE R IA IS Project No. G2369-42-01 June 5, 2020 LCIHV1E11 Next Med III, LLC JUN 112020 6125 Paseo Del Norte, Suite 210 Carlsbad, California 92120 LAND DEVELOPMENT Attention: Mr. Scott Leggett ENGINEERING Subject: RESPONSE TO THIRD-PARTY REVIEW COMMENTS CARLSBAD CORPORATE PLAZA PARKING STRUCTURE 6183 AND 6185 PASEO DEL NORTE CARLSBAD, CALIFORNIA Reference: 1. Geotechnical Investigation, Paseo Del Norte, Parking Structure, 6183 and 6185 Paseo Del Norte, Carlsbad, California, prepared by Geocon Incorporated, dated March 13, 2019 (Project No. G2369-42-01). Update to Geotechnical Investigation: 2019 CBC Seismic Design Parameters, Paseo Del Norte Parking Structure, 6183 and 6185 Paseo Del Norte, Carlsbad, California, prepared by Geocon Incorporated, dated January 13, 2020 (Project No. G2369-42-01). Precise Grading Plans for Carlsbad Corporate Plaza Parking Structure, 6183 - 6185 Paseo Del Norte, 6183 - 6185 Paseo Del Norte, Carlsbad, California, prepared by Pasco Laret Suiter & Associates, issue date January 30, 2020. Third Party Geotechnical Review (First), Proposed Parking Structure, 6183 and 6185 Paseo del Norte, Carlsbad, California, prepared by Hetherington Engineering, Inc., dated May 5, 2020 (Project ID: GR2020-0013). Dear Mr. Leggett: We prepared this letter to respond to third-party review comments provided in Reference 4 for the subject project. Each review comment followed by our response is presented below. Comment 1: Due to the age of the "Geotechnical Investigation..." (Reference 1), the Consultant should provide an updated geotechnical report addressing the plans, and provide updated grading and foundation recommendations consistent with the 2019 California Building Code, as necessary. Response: Based on our review of the referenced plans, the grading and foundation recommendations provided in References 1 and 2 remain applicable to the project. 6960 Flanders Drive 0 San Diego, California 92121-2974 U Telephone 858.558.6900 0 Fax 858.558.6159 Updated seismic design parameters for the 2019 California Building Code are provided in Reference 2. No additional updated recommendations are necessary at this time. Comment 2: The Consultant should review the project grading and foundation plans, provide any additional geotechnical recommendations considered necessary, and confirm that the plans have been prepared in accordance with the geotechnical recommendations provided in the referenced reports. Response: We have reviewed the project grading and foundation plans. Based on our review, the plans have been prepared in accordance with the geotechnical recommendations contained in References 1 and 2. No additional geotechnical recommendations are necessary. Comment 3: The Consultant should provide an updated geotechnical map/plot plan utilizing the latest grading plan for the project to clearly show (at a minimum) a) existing site topography, b) proposed structures/improvements, c) proposed finish grades, d) locations of the subsurface exploration, e) geologic contacts, andf) remedial grading limits, etc. Response: The requested geologic map is appended. We used a CAD file of Reference 3 as the base map. With respect to proposed finish grades, the majority of the existing parking lot will remain, therefore, finish grade matches existing grade. In pavement areas that are replaced, the new pavement surface will match the existing surface. With respect to remedial grading limits, remedial grading will only be performed within footing excavations. Comment 4: The Consultant should provide a statement with respect to the stability of the existing slopes. Response: The proposed parking structure is planned within an existing parking lot that only has about 3 feet of topographic relief across the building pad. The closest slopes to the parking structure (greater than 40 feet away) are along the northeast and east sides of the property and have heights of approximately 3 feet to 9 feet. These slopes also have an inclination 2:1 (horizontal to vertical) and flatter. The slopes are well vegetated and appear to be stable. The proposed project is not encroaching into or near these slopes. The project will not impact the stability of existing slopes. Comment 5: The Consultant should provide recommendations for temporary excavations (backcuts/ slopes, etc). Project No. G2369-42-01 -2- June 5, 2020 Response: As previously indicated, the proposed project is located in an existing parking lot that only has about 3 feet of topographic relief. The only excavations planned for the site are what are required to install footings and utility trenches. However, to satisfy the review comment, recommendations for temporary excavations are provided below. In general, special shoring requirements may not be necessary if temporary excavations will be less than 4 feet in height. It is the responsibility of the contractor and their competent person to ensure all excavations, temporary slopes and trenches are properly constructed and maintained in accordance with applicable OSHA guidelines, in order to maintain safety and the stability of the excavations and adjacent improvements. These excavations should not be allowed to become saturated or to dry out. Surcharge loads should not be permitted to a distance equal to the height of the excavation from the top of the excavation. The top of the excavation should be a minimum of 15 feet from the edge of existing improvements. Excavations steeper than those recommended or closer than 15 feet from an existing surface improvement should be shored in accordance with applicable OSHA codes and regulations. Comment 6: The Consultant should provide a statement confirming that the foundation and slab recommendations are consistent with the requirements of Section 1808.6 (expansive soils) of the 2019 California Building Code or revise the recommendations accordingly. Response: The foundation and slab recommendations are consistent with the requirements of Section 1808.6 of the 2019 CBC. Recommendations provided in Reference 1 are based on the on-site soil conditions. Revised recommendations are not necessary. Comment 7: The Consultant should provide a list of recommended geotechnical observations and testing during grading and construction. Response Recommended geotechnical observations and testing during grading and construction are the following: Observation and compaction testing during grading; Observation and compaction testing during utility trench backfill and wall backfill; Observation of foundation excavations; Compaction testing of concrete hardscape and curb subgrade; Compaction testing of pavement subgrade, base, and asphalt concrete. Project No. G2369-42-01 - 3 - June 5, 2020 If there are any questions regarding this correspondence, or if we may be of further service, please contact the undersigned at your convenience. Very truly yours, GEOCON iNCORPORATED C. OR .25M M rn (0y _CC_ M-ikesell GE 2533 OFC RCM:arm (e-mail) Addressee Project No. G236942-01 - 4 - June 5, 2020 PASEO DEL NORTE PARKING STRUCTURE CARLSBAD, CALIFORNIA N NN Us TTF \ /PROJECT AND - REMEDIAL GRADING 0' 25' 50' 75' 100' SCALE 1"_-r50'(on 11x17) 47~ _L : '1 W U q121C LL[ J:=~L[ — ~6c h t" I t - GEOCON LEGEND Qcf........COMPACTED FILL E3 bAPPROX. LOCATION OF EXPLORATORY BORING GEOCON INCORPORATED 4 GEOTECHNICAL • ENVIRONMENTAL U MATERIALS 6960 FLANDERS DRIVE SAN DIEGO, CALIFORNIA 92121- 2974 PHONE 858 558-6900- FAX 858 558-6159 PROJECT NO. G2369 - 42 - 01 FIGURE 1 GEOLOGIC MAP DATE 06 -05 - 2020 Plotted 06/05/2020 3 1 5PM I By:ALVIN LADRlLLOFdO I File LocabonY \PR0JECTS1G2369.42.01 (Paseo Del Norte Parkirrg)\SHEETS\G2369-42-01 Geo Map dwg