2020-065 - Adopting Environmental Findings of Fact

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The Warner Redhill Mixed -Use Project CEQA Findings of Fact The proposed Project would maintain the existing drainage pattern. The runoff from the Project area would be collected by roof drains, surface flow designed pavement, curbs, and area drains and conveyed Modular Wetland System units for treatment. The Modular Wetland System units contain catch basin inlet filters to capture trash, debris, gross solids and sediments, a settling chamber for separating out larger solids, and a media filter cartridge for capturing fine silts, metals, nutrients, and bacteria. The MS4 permit and DAMP require new development projects to prepare a WQMP (included as PPP WQ-2) that is required to include BMPs to reduce the potential of erosion and/or sedimentation through site design and structural treatment control BMPs. The proposed drainage system and adherence to the existing regulations would ensure that Project impacts related to alteration of a drainage pattern and erosion/siltation from operational activities would be less than significant. Plans, Program and Policies PPP WO-1: NPDES/SWPPP. As listed previously. PPP WO-2: WQMP. As listed previously. Impact Finding: The Project would not substantially alter the existing drainage pattern of the site or area, including through the alteration of the course of a stream or river or through the addition of impervious surfaces, in a manner which would substantially increase the rate or amount of surface runoff in a manner which would result in flooding on- or off -site (Draft EIR at p. 5.8-15). Facts in Support of Findings: Construction As described previously, implementation of the Project requires a SWPPP (included as PPP WQ- 1) that would address site specific drainage issues related to construction of the Project and include BMPs to eliminate the potential of flooding or alteration of a drainage pattern during construction activities. This includes regular monitoring and visual inspections during construction activities. Compliance with the Construction General Permit and a SWPPP prepared by a QSD and implemented by a QSP (per PPP WQ-1) as verified by the City through the construction permitting process would prevent construction -related impacts related to potential alteration of a drainage pattern or flooding on or off -site from development activities. Therefore, impacts would be less than significant. Operation The Project would maintain the existing drainage pattern by collecting runoff in roof drains, curbs, and area drains and conveying it to one of four Modular Wetland System units for treatment. Treated runoff would be conveyed to the existing 84-inch drain located within Red Hill Avenue. Although the Project related runoff conditions (flow rates and durations) would increase from predevelopment conditions (shown in Draft EIR Table 5.8-1), the Project would manage the increased flow with Modular Wetland System units that have been designed to accommodate the increased volume pursuant to the MS4 permit and DAMP requirements. The units would retain, filter, and slowly discharge runoff into the existing off -site drain. As part of the permitting approval process, the proposed drainage design and engineering plans would be reviewed by the City's Engineering Division to ensure that the proposed drainage would accommodate the appropriate design flows. Overall, the proposed drainage system and adherence to the existing City of Santa Ana May 2020