AgdaPkt 2017-01-09 Closed and Joint

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C. 7.A. - Page 67 before being carried through pipes to the media filter and vault. A 12 -inch storm drain would carry treated water from the media filter vault and storage vault to the City's storm drain on Bradford. (Plan Sheets A2. OC and A2.9,314116; Plan Sheet L1.2, 3/14/16; and Plan Sheets C8.00 and C9.00,3125116) ■ Utilities: Utility trench backfilling should be done under the observation of a California Registered Geotechnical Engineer. Ideally, backfill for the pipe zone (i.e., material beneath and immediately surrounding the pipe) should consist of native material less than 3/ inch in maximum dimension, when compacted in accordance with the recommendations for engineered fill provided above. (p. 16) ■ All site preparation, including demolition and stripping, should be performed under the observation of the Geotechnical Engineer, or their qualified field representative, and should be carried out according to the requirements defined by the City and contained within the Guide Contract Specifications (Appendix F of the ENGEO report). The final grading plans should be submitted to the Geotechnical Engineer for review. (p. 12) All plans and specification documents are subject to review and approval by the City. ■ ENGEO should review any changes made in the character; design or layout of the development to modify the conclusions and recommendations contained in this report, as necessary (p. 1). The existing geotechnical report prepared for the project, and any subsequent revisions, is subject to City review and approval, as would subsequent detailed excavation, earthwork, and foundation plans. In collaboration with the California Registered Geotechnical Engineer; the appropriate City staff would also observe on-site construction work. These conclusions are consistent with both the California Building Code (CBC) and the DTPPprogram EIR (Chapter 16, Geology and Soils). iv) The project site is relatively flat; therefore, no impacts from landslides are anticipated. In conclusion, the Downtown Precise Plan program EIR concluded that while the DTPP area could be subject to moderate to high susceptibility to ground shaking and liquefaction, the City's routine grading and building permit regulations provide reasonable assurances that individual projects would incorporate the design and engineering refinements necessary to reduce the potential impact of DTPP facilitated development to a less -than -significant level, requiring no additional mitigation. The site-specific geotechnical report prepared for the project, and any subsequent revisions, is subject to City review and approval, consistent with the CBC and the DTPPprogram EIR (Chapter 16, Mitigation 16-1). The project shall be subject to Downtown Precise Plan program EIR Mitigation 16-3, which shall be required as a condition of project approval. The mitigation requires the applicant to prepare an erosion control plan subject to City approval and consistent with the required San Mateo County Stormwater Pollution Prevention Plan (SWPPP) Best Management Practices. The plan shall be implemented during construction and would reduce the potentially significant impact on soil erosion and sedimentation to a less -than -significant level. No changes to geologic substructures are expected to occur as a result of project implementation. As described in item (a) above, the proposed project would comply with all applicable local and State codes and regulations, and project design would incorporate City -approved geotechnical recommendations for site development. Therefore, this impact is considered less than significant. All grading plans are subject to City review and approval. The Downtown Precise Plan program EIR (p. 16-6) determined that development within the DTPP area may be subjected to hazards from expansive soils, representing a potentially significant impact. Mitigation 16-1 requires that the final geotechnical report required by the City Building Official include an analysis of expansive soil hazards and recommended stabilization measures. Implementation of these measures, combined with conformance with standard CBC and other applicable State and local regulations (all of which shall be required as conditions of approval for the project) would reduce the potential effects of expansive soils to a less -than -significant level. The project -specific geotechnical report (ENGEO pp. 9 and 14) concludes that highly expansive soils underlying the base of the foundation are not expected to exhibit significant shrink -swell action due to the level of saturation and the magnitude of the permanent building loads. Because the parking garage would include excavation, the surfrcial soil on the large majority of the building footprint would be removed; however, at -grade improvements (e.g., sidewalks and flatwork) would be designed to address expansive soil. All of these recommended solutions are subject to City review and approval for feasibility and effectiveness. In addition, the DTPPprogram EIR (p. 16-8) noted that development occurring under the DTPP would be subject to damage due to the presence of corrosive soils within the DTPP area. Mitigation 16-2 specifies that buried metal infrastructure have cathodic protecting using a sacrificial anode system that conforms to Part VII (G) of the City's water system design criteria and standard specification details Section 02661. Additionally, concrete mixes must conform to Caltrans specifications for Protection of Reinforcement Against Corrosion Due to Chlorides, Acids, and Sulfates as outlined in the Memo to Designers 10-5, January 2002. These measures, which shall be required as conditions of approval for the project, would reduce the potential impacts of corrosive soils on the project to a less - than -significant level. 20