Abstract
This research evaluated storm water runoff water quality constituent data collected by industrial facilities under California's 1992 General Industrial Storm Water NPDES Permit. Data for 13 constituents were evaluated for a sample of 130 metal plating facilities in Los Angeles County, reported over a 3-year period. Results are intended as a screening level determination of several factors: proportion of facilities detecting the constituents; their concentrations in a single-industry, single-region set of facilities; and possible trends over time. The analysis also tested the limitations of the self-reported data, which report concentration rather than load and may not be representative of facility runoff. Zinc and copper were detected at more than 80% of facility locations; nickel, chromium, lead, and cadmium were detected at more than 25% of locations. Mean concentrations of copper, lead, zinc, suspended solids, and oil and grease at sample facilities testing for the constituents were roughly comparable to mean concentrations reported by US EPA for a similar set of data from a nationwide sample of metal products manufacturing facilities. As a fraction of water quality standards, median concentration at facilities detecting the constituents were relatively high for copper and silver compared to standards for aquatic life, and for cadmium and lead compared to human drinking water standards. Trends over the 3-year period in concentration of pollutants in facility runoff that may result from regulatory pollution prevention requirements were inconclusive. The concentration data show evidence of other confounding influences sufficiently large and systematic to obscure possible trends in pollutant reduction.
