2019-047 - Adopting Mitigated Negative Declaration Environmental Review No. 2018-75

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from the site due to the increase of impervious surface area on the site. Although the project would increase the quantity of surface water runoff that would be generated, the project proposes to retain the increased volume of runoff on -site and incrementally release the runoff over time to equal the existing condition. Therefore, project generated runoff would not exceed or impact the capacity of the existing downstream storm water drainage system in Sunflower Avenue and the Santa Ana - Delhi storm channel. Table 10 Peak Flow Comparison Summary Storm Event Existing Condition (cfs) Proposed Condition (cfs) Difference (cfs) 2-year 2.5 2.75 0.25 25- ear 6.02 6.59 0.57 100- ear 7.79 8.59 0.80 The project would be required to treat surface water runoff prior to its discharge to meet Regional Water Quality Control Board water quality requirements and provide safeguards that surface water runoff would not provide sources of polluted runoff. As discussed in section "IX.a)" above, a preliminary WQMP has been prepared and states that a proposed Modular Wetlands Biofiltration System would be installed to remove and prevent most project generated pollutants from the storm water prior to being discharge from the site into the local storm drain system in Sunflower Avenue adjacent to and south of the site. The installation and maintenance of the BMPs in compliance with the preliminary WQMP would reduce and filter most project runoff pollutants. The project would not impact surface water quality. iv Impede or redirect flood flows? Less Than Significant. The project is not located within a designated flood hazard zone. The project does not propose and would not alter the existing drainage patterns on the site or any other flows that would impede or redirect any flood flows. The existing drainage patterns on the site would be maintained and project generated stormwater flows would continue south to Sunflower Avenue. d) In flood hazard, tsunami, or seiche zones, risk release of pollutants due to project inundation? No impact. There are no bodies of water adjacent to or in close proximity to the site that could impact the project due to a seiche. The site is approximately 6.5 miles northeast of the Pacific Ocean and approximately 35' above mean sea level. The Santa Ana General Plan does not identify any portion of the city at risk due to a tsunami. There are no hillsides or other geotechnical conditions either on or adjacent to the project that would inundate the site due to a mudflow. The project would not be impacted by a seiche, tsunami, or mudflow. e) Conflict with or obstruct implementation of a water quality control plan or sustainable groundwater management plan? Less Than Significant Impact. The project developer has prepared a Preliminary WQMP" and the project developer would be required by the city to install and implement all proposed water quality collection and surface water runoff treatment measures listed in the WQMP. As a result, the project would not conflict with or obstruct water quality control measures mandated by the state. zs City of Santa Ana/Santa Ana Region Priority Project, Preliminary Water Quality Management Plan (WQMP), Legacy Sunflower, 651 Sunflower Avenue, Santa Ana, California, C&V Consulting, November 2018. Legacy Sunflower Apartments Page 62 Mitigated Negative Declaration — March 14, 2019