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Home My WebLink AboutSDP 2018-0020; 540 CHESTNUT AVE; RESPONSE TO CITY OF CARLSBAD THIRD PARTY GEOTECHNICAL REVIEW (FIRST) COMMENTS FROM HETHERINGTON ENGINEERING INC.; 2020-05-15May 15, 2020 BG Consolidated Attention: Mr. Tom Gaeto 1441 Montiel Road, Ste 115 Escondido, California 92026 Telephone: (760)746-4955 cc: David Caron-Civil Landworks: dave@civillandworks.com Subject: Response to City of Carlsbad Third-Party Geotechnical Review (First) Comments from Hetherington Engineering, Inc. Project Number: 9096.1 Dated April 2, 2020, Project ID: GR2020-0009 540 Chestnut Avenue Carlsbad, California References: At the end of document. Mr. Gaeto: As requested, Construction Testing & Engineering, Inc. (CTE) provides the following responses to the City of Carlsbad review comments. Responses below are in response to Third-Party Geotechnical Review (First) dated April 2, 2020. Applicable responses are provided below and are numbered based on the comment numbers enumerated in the third-party city review. GEOLOGY RESPONSES: No. 1: 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. Response to No. 1: CTE has reviewed the referenced grading plans and finds them to be in substantial conformance with CTE's geotechnical recommendations provided in the referenced report. No exceptions were noted. CTE has not yet been provided structural plans for review, but anticipates performing a geotechnical review of them once available. No. 2: The Consultant should provide an updated geotechnical map/plot utilizing the latest grading plan-for the project to clearly show (at a minimum) a) existing site topography, b) proposed structure/improvements, c) proposed finished grades, d) locations of the subsurface exploration, e) geologic contacts, and f) remedial grading limits, etc. 1441 Montiel Road, Suite 115 1 Escondido, CA 92026 I Ph (760)746-4955 I Fax(760)746-9806 I www.cte.inc.net RECORD 'cOPY 1 Construction Testing & Engineering, Inc. Initial Date Inspection I Testing I Geotechnical I Environmental & Construction Engineering I Civil Engineering I Surveying CTE Job No. 10-13921S Response to Third-Party Geotechnical Review (First) . Page 2 Proposed Residential Development 540 Chestnut Avenue, Carlsbad, California May 15.2020 CTE Job No. 10-13921S Response to No. 2: An updated geotechnical map/plot utilizing the latest grading plan for the project that shows existing site topography, proposed structur'e/imprôvements, proposed finished grades, locations of the subsurface explorations, geologic units, and remedial grading limits is provided as Figure 2. No. 3: The Consultant should provide a detailed description of proposed site grading, structures/improvements, etc. Response to No. 3: The site as currently proposed is to consist of three residential structures founded on conventional shallow foundations properly embedded into compacted fill 'materials. Typical additional improvements such as exterior pavements and flatwork, utilities, and landscaping are also proposed. As recommended 'in CTE's referenced report, site grading is anticipated to consist of a two foot or deeper overexcavation prior to placement of engineered fill in compacted lifts. No. 4: The Consultant should address whether the site is considered a "Near Fault Site" in accordance with 2019 CBC, Section 1803.5.12. Response to No. 4: Based on distance to the Rose Canyon Newport Inglewood Fault Zone, which is approximately four kilometers to the west, the site may be considered a near-fault site as defined by ASCE 7-16, Section 11.4.1. I No. 5: The Consultant should provide the site Risk Category and Seismic Design Category consistent with the 2019 CBC. Response to No. 5: In accordance with the 2019 CBC Table 1604.5, Risk Category II is applicable for the site and improvements. Based on the Risk Category and design spectral response acceleration parameters, SDS and SDI, Seismic Design Category D is assigned for the site structures in. accordance with ASCE 7-16, Section 11.6. No. 6: The Consultant should provide a statement regarding the impact of the proposed grading and construction on adjacent properties and improvements. Response to No. 6: Based on CTE's review, the proposed grading shown on the referenced grading plans is not anticipated to detrimentally impact adjacent properties or improvements, provided CTE's previous and future (provided as necessary and as requested) geotechnical recommendations are implemented. No. 7: The recommended coefficient of friction exceeds 2019 CBC presumptive values. The Consultant should justify or update -as necessary. Response to No. 7: As per table 1, page 7.2-63 of the referenced design manual (NAVFAC, 1986), the range of friction factors for mass concrete on silty fine- to medium-sand is 0.35 to 0.45. CTE considers our recommended value of 0.30 to be conservative. S:\Projects\IO-1 3000 to 10.13999 Projects\10- 13921 S\CommentsLtr_Rcsponse to ReviewComments.doc Response to Third-Party Geotechnical Review (First) Page 3 Proposed Residential Development 540 Chestnut Avenue, Carlsbad, California May 15, 2020 CTE Job No. 10-13921S No. 8: The Consultant should provide a minimum slab thickness for exterior hardscape. Response to No. 8: Exterior hardscape should measurea minimum of 4.5 inches in thickness. No. 9 The Consultant should provide a list of recommended observation and testing during the site grading and construction. Response to No. 9: As is typical and at a minimum, a CTE geotechnical representative should observe and approve the dimensions and bottoms of excavations for overexcavation, footings, utilities, and other subsurface features. Additionally, CTE should be scheduled by others to test field relative compacti9n and moisture content of placed engineered fill soils, and should be allowed to collect additional geotechnical samples, as necessary and appropriate. CTE should observe and verify site conditions during construction. This report is subject to the same limitations as our previous project geotechnical documents. We appreciate the opportunity to be of service on this project. Should you have any questions or need further information please do not hesitate to contact this office. Respectfully submitted, CONSTRUCTION TESTING & ENGINEERING, INC. Jay F. Lynch, CEG #1890 Principal Engineering Geologist CJKJJFL:ack ti (o No.84406 Colm J Kenny, RCE #84406 Dr. 30 i 1301- Senior Engineer J• Figure 2 Updated Geotechnical Map S:\Projects\IO-I3000 to 10-13999 Projects\I0-I3921S\Comments\Ltr_Response to Review Comments.doc Response to Third-Party Geotechnical Review (First) Page 4 Proposed Residential Development S 540 Chestnut Avenue, Carlsbad, California May 15, 2020 CTE Job No. 10- 13 921 S REFERENCES: Geotechnical Investigation Proposed Residential Development 540 Chestnut Avenue, Carlsbad, California CTE Job No. 10-13921S, dated February 25,2020 Review of Grading Plans and Drainage Design 540 Chestnut SFR 540 Chestnut Avenue, Carlsbad, California CTE Job No. 10-13921 S, dated January 17, 2019 Preliminary Grading Plans For: 540 Chestnut Avenue SFR Prepared by Civil Landwórks, dated December 18, 2018, updated February27, 2020 City of Carlsbad . . . . 1st REVIEW FOR V 2018-0010/SDP 2018-0020 (DEV2017-Q138)-540 CHESTNUT SFR * 540 Chestnut Avenue, Carlsbad, California S S Dated October 25, 2018. Foundations & Earth Structures Design Manual 7.02 Naval Facilities Engineering Command (NAVFAC), dated September 1, 1986 S:'.Project.s\lO- 13000 to 10-13999 Projects\10- 1392 I5\CommentsLtr_Response to Review Commcnts.doc