Water Quality Assessment for the California Department of Transportation San Diego Region

The California Department of Transportation (Caltrans) District 11 discharges storm water from facilities and properties within its right-of-way to various waterbodies in the San Diego area. The impact of these discharges on the waterbodies varies according to the Caltrans activity, waterbody beneficial uses, and existing water quality conditions. To minimize this impact and provide the most benefit to the waterbody, constituents and waterbodies of concern for storm water discharges from Caltrans facilities in District 11 were identified. Identification of constituents and waterbodies was based on an assessment of Caltrans discharges as compared to impaired waterbody listings (303(d) list, etc.) and receiving water and storm water studies conducted by local and regional agencies. Stormwater monitoring data collected from Caltrans facilities throughout Southern California were used as the basis for the water quality assessment. When sufficient data were available for a constituent, the 95^th percentile concentration was determined and compared to water quality objectives outlined in the Water Quality Control Plan for the San Diego Region (Basin Plan). Constituents with 95^th percentile concentrations exceeding appropriate objectives (assuming no dilution) were considered potential constituents of concern for Caltrans discharges.