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Home My WebLink AboutPD 2021-0004; NORTH COUNTY ACADEMY; RESPONSE TO REVIEW COMMENTS-THIRD PARTY GEOTECHNICAL REVIEW; 2021-06-02U . GEOTECHNICAL MATERIALS SPECIAL INSPECTION I Carlsbad Unified School District June 2, 2021 Mr. Derrick Anderson NOVA Project 2020187 6225 El Camino Real Carlsbad, CA 92009 Subject: Response to Review Comments - Third Party Geotechnical Review North County Academy, Campus Consolidation 1640 Magnolia Avenue, Carlsbad, California References: Hetherington 2021. THIRD PARTY GEOTECHNICAL REVIEW (FIRST), Proposed Portable Classrooms, 1640 Magnolia Avenue, Carlsbad, California, Hetherington Engineering, inc., Project No. 9296. 1, February 9, 2021. MBI 2021. Review/Redlines by Michael Baker International of: Priority Development Project (POP) Storm Water Quality Management Plan (SWQMP) for North County Academy - Campus Consolidation prepared by PLSA, dated December 17, 2020. NOVA 2020. Report, Preliminary Geotechnical Investigation, Proposed Portable Classrooms, North County Academy, 1640 Magnolia Avenue, Carlsbad, CA 92008, NOVA Services, Inc., Project No. 2020187, December 7, 2020. NOVA 2021. Update Report, Geotechnical Investigation, North County Academy, Campus Consolidation, 1640 Magnolia Avenue, Carlsbad, CA, NOVA Services, Inc., Project No. 2020187, June 2, 2021. PLSA 2021. Grading Plans For: North County Academy, Campus Consolidation, 1640 Magnolia Avenue, Carlsbad, California, Pasco Laret Suiter & Associates, Inc., Project No. 687995, undated, received by NOVA May 11, 2021. Dear Mr. Anderson: The intent of this letter is to respond to comments by Hetherington Engineering, Inc. regarding its review of the above-referenced geotechnical reporting and plans. The comments by Hetherington Engineering were provided under cover of a letter dated February 9, 2021 and are referenced herein as 'Hetherington 2021.' Based on the revisions to the geotechnical map in response to Review Comment 2, as well as revisions to storm water recommendations, which were made in response to a separate review of the SWQMP by Michael Baker International, (MBi 2021) the project geotechnical report has been updated (NOVA 2021). NOVA Services, Inc. (NOVA) is retained by Carlsbad Unified School District as Geotechnical Engineer-of-Record (GEOR) for the project. 4373 Viewridge Avenue, Suite B www.usanova.corn 24632 San Juan Avenue, Suite 100 San Diego, CA 92123 Dana Point, CA 92629 P: 8582927575 P: 9493887710 I . Response to Third Party Geotechnical Review Comments All, North County Academy, Carlsbad, CA NOVA Project 2020187 NOVA June 2, 2021 T.Y4 I 'AK€ó1'!I II The following text reproduces comments in Hetherington 2021 regarding geotechnical-related design for the above-referenced project. Comments from Hetherington 2021 are reproduced below in italics, following which a response is provided by NOVA. Comment 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 1. NOVA has reviewed the grading plans (PLSA 2021). The review by NOVA was limited to the geotechnical aspects of the grading plans, reviewing for conformance with the referenced geotechnical reporting. Based upon this review, it is NOVA's judgment that PLSA 2021 has been prepared in accordance with the recommendations of NOVA 2020 and NOVA 2021. Comment 2. The Consultant should provide an updated geotechnical map/plot plan utilizing the last grading plan for the project to clearly show (at minimum), a) existing site topography, b) proposed structures/improvements, c) proposed finished grades, d) locations of the subsurface exploration, e) geologic contacts, and 0 remedial grading limits, etc. Response 2. The requested geotechnical map and cross-sections are attached to this response letter as Plate 1 and Plate 2. Comment 3. The Consultant should address moisture vapor retarder/barrier underlayment recommendations for the conventional slab on grade. Response 3. Soil moisture vapor that penetrates ground-supported concrete slabs can result in damage to moisture-sensitive floors, some floor sealers, or sensitive equipment in direct contact with the floor. It is not the responsibility of the geotechnical consultant to provide recommendations for vapor retarders to address this concern. This responsibility usually falls to the Architect. Decisions regarding the appropriate vapor retarder are principally driven by the nature of the building space above the slab, floor coverings, anticipated penetrations, concerns for. mold or soil gas, and a variety of other environmental, aesthetic, and materials factors known only to the Architect. A variety of specialty polyethylene (polyolefin)-based vapor retarding products are available to retard moisture transmission into and through concrete slabs. This remainder of this section provides an overview of design and installation guidance, and considers the use of vapor retarders in the building construction in the San Diego area. Detail to support selection of vapor retarders and to address the issue of moisture transmission into and through concrete slabs is provided in a variety of publications by the American Society for Testing and Materials (ASTM) and the American Concrete Institute (Ad). A partial listing of those publications is provided below. I Response to Third Party Geotechnical Review Comments North County Academy, Carlsbad, CA NOVA Project 2020187 NOVA. June 2, 2021 . ASTM El 745-97 (2009). Standard Specification for Plastic Water Vapor Retarders Used in Contact with Soil or Granular Fill under Concrete Slabs. . ASTM El 54-88 (2005). Standard Test Methods for Water Vapor Retarders Used in Contact with Earth Under Concrete Slabs, on Walls, or as Ground Cover. ASTM E96-95 (2005). Standard Test Methods for Water Vapor Transmission of Materials. ASTM E1643-98 (2009). Standard Practice for Installation of Water Vapor Retarders Used in Contact with Earth or Granular Fill Under Concrete Slabs. . ACI 302.2R-06. Guide for Concrete Slabs that Receive Moisture-Sensitive Flooring Materials. Vapor retarders employed for ground supported slabs in the San Diego are commonly specified as minimum 10 mil polyolefin plastic that conforms to the requirements of ASTM E1745 as a Class A vapor retarder (i.e., a maximum vapor permeance of 0.1 perms, minimum 45 lb/in tensile strength and 2,200 grams puncture resistance). Among the commercial products that meet this requirement are the series of Yellow Guard® vapor retarders vended by Poly- America, L.P.; the Perminator® products by W. R. Meadows; and Stego®Wrap products by Stego Industries, LLC. The person responsible for design of the vapor barrier should consult with product vendors to ensure selection of the vapor retarder that best meets the project requirements. For example, concrete slabs with particularly sensitive floor coverings may require lower permeance or other performance-related factors are specified by the ASTM El 745 class rating. The performance of vapor retarders is particularly sensitive to the quality of installation. Installation should be performed in accordance with the vendor's recommendations under full- time surveillance. NOVA hopes the responses to the Hetherington's review comments are clear. Should you have any questions regarding this letter or other matters, please do not hesitate to contact the undersigned at 858.292.7575. Sincerely, NOVA Services, Inc. Melissa Stayner, CEG " Senior Engineering Geologist / / Attachment: Plates 3 t "I I /- / Jhn F. O'Brien, P.E, G.E. tPincipal Geotechnical Engineer N. Response to Third Party Geotechnical Review Comments Alb, North County Academy, Carlsbad, CA NOVA Project 2020187 NOVA June 2, 2021 \\ / I A — : ---- - - -- ---------------- A MATERIALS SPECIAL INSPECTION NOVA. 4373 VMwrog Avsrie, 5ufti B Sian Deo, CA .922$ F; 853.292.7575 944 CSI AITanocer. Suite F SarI Giit, CA 92373 F; 94S,388,77 10 www.uaa-ncva.com KEY TO SYMBOLS Qop OLD PARALIC DEPOSITS 8-4 €4 GEOTECHNICAL BORING P-2 0 PERCOLATION TEST BORING f\J LIMITS OF ANTICIPATED REMEDIAL GRADING B B'! GEOLOGIC CROSS-SECTION 0 20' 40' LLI PROJEC3 NO.: 2020137 DATE: JUNE 2021 DRAWN BY: DTJ REVIEWED BY: MS SCALE: DRAWING TITLE; SUBSURFACE INVESTIGATION MAP PLATE NO. 1 OF 2 KEY TO SYMBOLS Qop OLD PARALIC DEPOSITS 3.4 I GEOTECHNICAL BORING P.2 .1. PERCOLATION TEST BORING EXISTING GRADE f\J PROPOSED GRADE GEOLOGIC CONTACT A A' 180 - - 180 PROPOSED 170 - MODULAR BUILDINGS - 170 160 B-2 TU 160 TOPSOIL 150 - - 150 140 - TD2i.5 Qop TD=2t5 - 140 130 - - 130 120 I I 120 0 10 20 30 40 50 60 70 80 90 100 110 180 180 PROPOSED BIO BASIN PROPOSED MODULAR BUILDINGS 170 - - 170 ::: 160 TOPSOIL-" - 150 Qop 140 - TD21.5 Qop TD=21,5' 140 130 — —130 120 I 1 1 I I I I I I 120 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 160 170 180 jA SPECIAL MATEWALS lti$PECTION NOVA. 4373 Viwrdgs Avenue, Sfta B San Dann. CA 9223 P: 55E2927575 944 Cane Amanocer, Sue F San Clemente, CA 92573 P: 949388.770 www.uaancva.com ci C,) C-) I >- W2 __j O >-° co o co Qo I F- 0 z PRO JECT NO.: 2020181 DATE JUNE 2021 DRAWN BY: DTJ REVEWEDBY: MS SCALE: I DRAWING flTLE: CROSS-SECTIONS AA '& BB 0 20 40 LATE NO. 20F2