2024-053 - Final Supplemental for The Related Bristol Specific Plan Project

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Facts in Support of Findings: Construction The existing NPDES Construction General Permit and Orange County DAMP require preparation and implementation of a SWPPP by a Qualified SWPPP Developer for the proposed construction activities (included as PPP WQ-1). The SWPPP is required to address site -specific conditions related to potential sources of sedimentation and erosion and would list the required BMPs that are necessary to reduce or eliminate the potential of erosion or alteration of a drainage pattern during construction activities to a less than significant level. In addition, a Qualified SWPPP Practitioner (QSP) is required to ensure compliance with the SWPPP through regular monitoring and visual inspections during construction activities. The SWPPP would be amended and BMPs revised, as determined necessary through field inspections, in order to protect against substantial soil erosion, the loss of topsoil, or alteration of the drainage pattern. Compliance with the Construction General Permit and a SWPPP prepared by a Qualified SWPPP Developer (QSD) and implemented by a QSP (per PPP WQ-1) would prevent construction -related impacts related to potential alteration of a drainage pattern or erosion from development activities. Overall, with implementation of the existing construction regulations that would be verified by the City during the permitting approval process, impacts related to alteration of an existing drainage pattern during construction that could result in substantial erosion, siltation, and increases in stormwater runoff would be less than significant (Draft Supplemental EIR at pp. 5.7-13 through 5.7- 14). Operation The Project -specific Preliminary WQMP describes that the Project site currently includes 37.02 acres of impermeable surfaces, which equates to 40 percent of the site. After completion of Project construction, the site would have a 4 percent reduction in impermeable surfaces (i.e., 35.37 acres or 86 percent of the site would have impermeable surfaces). The proposed Project would maintain the existing drainage pattern. The Project includes offsite storm drain improvements pursuant to the City's Storm Drain Master Plan that involve replacing 2,230 lineal feet of the 54,/60-inch storm drain with a 72-inch lateral in Sunflower Avenue and replacing a 42-inch lateral in Plaza drive with a 6041nch lateral. Treated runoff would be conveyed to the existing and upsized City of Santa Ana storm drains in the roadways adjacent to the site. From there, flows would travel to the Orange County Flood Control District Santa Ana — Gardens and then the Delhi Channel that drains to Newport Bay and the Pacific Ocean. The MS4 permit and DAMP require new development projects to prepare a WQMP (included as PPP WQ-3) that is required to include BMPs to reduce the potential of erosion and/'or sedimentation through site design and structural treatment control BMPs. Overall, 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 (Draft Supplemental EIR at pp. 5.7-14 through 5.7-15).