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98 CONCLUSION With regards to the issue area of Hydrology and Water Quality, the following findings can be made: (1) no peculiar impacts to the Commercial Component or its site have been identified, (2) there are no potentially significant effects or off-site and/or cumulative impacts which were not discussed by the EIR/SEIR, (3) no substantial new information has been identified which results in an impact which is more severe than anticipated by the EIR/SEIR, and (4) feasible mitigation measures contained within the EIR/SEIR would be applied to the project component and render its specific impacts less than significant. For these reasons, the hydrology and water quality impacts of the Commercial Component would be consistent with the impacts identified in the EIR/SEIR and this project component does not require additional environmental review under CEQA Guidelines section 15183. Housing Component: a. The Focused GPU EIR found that with continued implementation of the adopted General Plan goals, policies and programs, and the City’s development review process, the potential impacts of the Focused General Plan Update on local and regional water quality from future development within the planning area would be reduced to less than significant levels. The Project would not violate any water quality standards or waste discharge requirements or otherwise substantially degrade surface or ground water quality. The Housing Component site is located within an urban setting, which is served by an existing storm drain system that outfalls into San Francisco Bay. As described in the Housing Component Utility Report (Luk & Associates, “Utility Report, Residential Building, 920 Shasta Street, Redwood City, CA 94063, Luk Job#: 22158A10,” June 16, 2023), there is no existing underground storm drain piping adjacent to the subject site along either street frontage (Buckeye Street and Shasta Street). The site currently drains overland from southeast to northwest into the street gutter on Buckeye Street. Runoff from the site that travels into the street gutter, passes through a storm drain culvert under the Caltrain tracks, and continues north to ultimately drain into San Francisco Bay. The Housing Component would install onsite storm drain piping that connects to the existing Shasta Street and Buckeye Street gutters via a shallow onsite storm drain network (Luk & Associates, p. 5). Street gutter runoff would be collected in a Silva Cell system (i.e., a modular suspended pavement system that treats stormwater onsite), set behind the curb line and below the gutter pan. The Silva Cell system would capture and retain runoff within the cells. According to the Utility Report, any high flows would overtop the downstream curb-opening and flow down the street, matching the existing drainage pattern (p. 5). Any water left standing would be removed first through evapotranspiration (evaporation via the air and plants) and then by soil infiltration. The proposed onsite storm drain system would facilitate runoff infiltration at a rate that would ensure ponded water captured in the proposed Silva Cell system would drain into sub-soils within a 48-hour period. The proposed Housing Component would not contain uses that involve the discharge of cooled/heated water or pollutant-laden runoff. However, given the local urbanized area, the existing stormwater flows contain urban runoff with contaminants such as oil, grease, particulates, metals, and solvents. Because the Housing Component is subject to the requirements of a National Pollutant Discharge Elimination System (NPDES) permit for municipal stormwater runoff and other requirements of the City, County, and Regional Water Quality Control Board, the conditions of which limit the volume of contaminants allowed to enter the storm drain system, the proposed Housing Component would not violate any water quality standards or waste discharge requirements. Furthermore, the Focused GPU program EIR (pp. 4.10-17 and 4.10-18) concluded that Focused GPU-facilitated development would not result in any significant water quality or stormwater drainage impacts. The proposed Housing Component is in compliance with all applicable Focused GPU standards relevant to hydrology and water quality, and as a result, water quality and stormwater drainage impacts would be less than significant. The City’s Drainage Guidelines for Residential Development require, to the extent practicable, that post-development peak runoff rate and average volume of runoff be maintained at levels that are similar to pre-development levels. Also, the City mandates that proposed site conditions maintain the same runoff for the 30-year storm event as compared to the existing 10-year event. Stormwater runoff collected on the project site currently drains, and would continue to drain, to street gutters in the City stormwater system (Luk & Associates, p. 5). As required by the City of Redwood City Stormwater Management and Discharge Control Program Ordinance (Redwood City Municipal Code Chapter 27A), Housing Component approval requires that stormwater control measures be designed and sized to treat runoff from the entire project site using flow- or volume-based sizing criteria, subject to review and approval by the City and consistent with the San Francisco Bay Region Municipal Regional Stormwater NPDES Permit (MRP) Provision C.3.d. ATTY/RESO.0031/CC RESO CEQA GUIDELINES (901 EL CAMINO REAL) REV: 04-22-25 VR Page 98 of 148