Appendix A Water Quality Memo - Laserfiche WebLink

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21 sweeping. Structural source control BMPs include use of efficient irrigation systems and landscape design, water conservation, smart controllers, and source control. A Final Water Quality Management Plan would be prepared and the BMPs refined during final design. The BMPs would target and reduce constituents of concern from transportation facilities in compliance with the North Orange County MS4 Permit requirements. Therefore, when operational BMPs are implemented in accordance with NPDES Permit requirements as stipulated in Measure WQ-3, the proposed Project is not anticipated to result in long-term adverse impacts to water quality. 4.6 Cumulative Impacts Cumulative development in the Lower Santa Ana River Watershed is a continuation of the existing urban pattern of development that has already resulted in extensive modifications to watercourses in the area. The area’s watercourses have been channelized, and drainage systems have been put into place to respond to the past urbanization that has occurred in this area. For all cumulative analysis related to hydrology and water quality, the cumulative projects being considered include all potential projected development discharging to the Lower Santa Ana Watershed. Because cumulative hydrology and water quality impacts are caused by build out of properties that increase impervious area and pollutant loads, cumulative development is considered to be the build out of the Lower Santa Ana River over an extended period of time, resulting in development of all available parcels consistent with local and regional plans. New development and redevelopment can result in increased urban pollutants in dry-weather and stormwater runoff from project sites. Each project must comply with NPDES permitting requirements and include BMPs to avoid impacts to water quality and local hydrology in compliance with local ordinances and plans adopted to comply with requirements of the various NPDES permits. Specifically, all projects that disturb one acre or more of soil must comply with the CGP. Caltrans projects must comply with the Caltrans MS4 Permit. Local projects within the cities and the county must comply with the North Orange County MS4 Permit. Each project must consider impaired receiving waters and annual TMDL loads for receiving waters. The TMDL program is designed to identify all constituents that adversely affect the beneficial uses of waterbodies and then identify appropriate reductions in pollutant loads or concentrations from all sources so that the receiving waters can maintain/attain the beneficial uses in the Basin Plan. Thus, by complying with TMDLs, a project’s contribution to overall water quality improvement in the Lower Santa Ana Watershed in the context of the regulatory program is designed to account for cumulative impacts. Regional programs and BMPs such as TMDL programs and the MS4 Permit Program have been designed under an assumption that the Lower Santa Ana River Watershed would continue its pattern of urbanization. The regional control measures contemplate the cumulative effects of proposed development. The proposed Project would be required to comply with the requirements of the CGP and the North Orange County MS4 Permit and implement construction and operational BMPs to reduce pollutants in stormwater runoff. Compliance with these regional programs and permits constitutes compliance with programs intended to address cumulative water quality impacts. Each cumulative project would be required to develop a SWPPP (for construction), a WQMP (for local projects) or Storm Water Data Report (for Caltrans projects), and would be evaluated individually to determine appropriate BMPs and treatment measures to avoid impacts to surface water quality. Because the proposed Project’s disturbance area and increase in impervious area is minimal and includes BMPs to reduce pollutants of concern in runoff from the Project area during construction and operation, the proposed Project’s contribution to cumulative water quality impacts is not anticipated to be substantial.