Industrial storm water benchmark pollution exceedances in regional water quality control board nine, 2007 to 2014

Stormwater runoff from urbanized areas is a significant environmental problem, caused by large man-made impervious areas that collect metals, sediments, debris, organic pollutants, and nutrients that are the byproduct of a variety of everyday human activities. When it rains, these pollutants flush into waterways and eventually into coastal embayments and the ocean. Urban stormwater runoff is one of the leading anthropogenic sources of water pollution in the United States. Stormwater pollution has been shown to degrade aquatic habitats, alter waterway morphology and effect human health. In this study, stormwater pollutant concentrations were examined for twenty-three parameters from sixty-seven industrial facilities located in the jurisdiction of the San Diego Regional Water Quality Board from 2007 to 2014. Reported concentrations exceeded benchmark values listed in the federal Multi-Sector General Permit for Stormwater Discharges Associated with Industrial Activity (MSGP) 29.4 % of the time. Individual parameters had exceedance rates that varied from 0% to 100%. No significant temporal trend could be detected in the frequency of benchmark exceedances, indicating that there was no improvement of runoff water quality from the industrial facilities during this period. The number of antecedent dry days was significantly associated with higher exceedance frequencies, indicating a first flush effect on stormwater quality. On the other hand, no relationship was observed between rainfall magnitude and pollutant exceedance. These results suggest that the design standards on which the prior California Industrial General Permit is based may be insufficient to effectively prevent industrial stormwater pollution. New performance standards have been added to the new California Industrial General Permit effective July 1, 2015, including Numeric Action Levels (NALs) based on benchmark values in the federal MSGP. Exceedance of these NALs will trigger the requirement to implement enhanced best management practices (BMPs) under the supervision of a certified stormwater professional. The results of this study also provides a baseline for further evaluation of the efficacy of the new performance standards in the California Industrial General Permit.