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SAN LEANDRO SHORELINE DEVELOPMENT EIR ADDENDUM PROJECT CITY OF SAN LEANDRO May 2022 Page 39 e) Create or contribute runoff water which would exceed the capacity of existing or planned stormwater drainage systems or provide substantial additional sources of polluted runoff? f) Otherwise substantially degrade water quality? g) Place housing within a 100-year flood hazard area as mapped on a federal Flood Hazard Boundary or Flood Insurance Rate Map or other flood hazard delineation map? h) Place within a 100-year flood hazard area structures which would impede or redirect flood flows? i) Expose people or structures to a significant risk of loss, injury or death involving flooding, including flooding as a result of the failure of a levee or dam? j) Inundation by seiche, tsunami, or mudflow? Comments: HYDRO-a, b. The Certified EIR concluded that the construction and operational impacts associated with the demolition of existing structures and construction of new structures could result in impacts to water quality and waste discharge attributed to water pollution from soil erosion and increased stormwater runoff. As discussed in the Certified EIR, landside development within the Project area would be required to comply with State and local water quality regulations designed to control erosion and protect water quality during construction. This includes compliance with the requirements of the NPDES General Permit, which requires preparation and implementation of a Stormwater Pollution Prevention Plan (SWPPP). The Modified Project, which does not alter the footprint of existing buildings on the project site, would be subject to the same construction conditions as those identified in Chapter 4.8, Hydrology and Water Quality, of the Certified EIR and would not require the implementation of additional mitigation measures. Compliance with local and State regulatory requirements and implementation of construction BMPs would minimize discharges during the construction phase of the Modified Project and would not result in the degradation of water quality in receiving waters. Therefore, landside construction related impacts associated with the Modified Project would not result in a new impact or a substantial increase in magnitude of the existing impacts violating any water quality standards or waste discharge requirements or otherwise substantially degrade surface or ground water quality. The Certified EIR project found that waterside construction and demolition associated with the existing marina, docks, and piers would have the potential to result in temporary water quality impacts. The removal of piers and pilings would result in the temporary re-suspension of sediments and associated increase in turbidity levels and waterside construction activities could release chemicals and hydrocarbons, temporarily degrading water quality. Impacts resulting from turbidity and the release of chemicals and hydrocarbons were found to be a significant impact, which were reduced to a less than significant impact through the implementation of Mitigation Measure HYDRO-1A and Mitigation Measure HYDRO-1B. The Modified Project would also implement Mitigation Measures HYDRO-1A and HYDRO-1B, and therefore removal of piers and pilings and waterside construction related impacts would not result in a new impact or a substantial increase in magnitude of the existing impacts. The Certified EIR found that operational impacts associated with the removal of the marina and associated boats, piers, and docks would have a beneficial impact on water quality. However, post- construction operational impacts from landside development of the project could affect drainage patterns and increase the overall amount of impervious surface, thus creating changes to stormwater