PRIORITY POLLUTANT LOADS FROM EFFLUENT DISCHARGES TO THE SAN-FRANCISCO ESTUARY

Effluent monitoring data collected under the National Pollutant Discharge Elimination System (NPDES) Program were used to estimate pollutant loads from effluent discharges to the San Francisco Estuary for the period of 1984-1987. Most analyses of priority pollutant concentrations in effluents yielded "below detection limit" (BDL) results. Although many pollutants were monitored in effluents, quantitative assessment of spatial and temporal trends in loads could only be performed for four pollutants (chromium, copper, nickel, and zinc) that were detected in more than 50% of analyses. Four municipal wastewater treatment facilities accounted for approximately 50% of the total loads of these elements to the Estuary. Statistically significant declines in loads from some of the largest dischargers were observed. Modifications to procedures for collecting and reporting effluent monitoring data that would enhance the value of these data in assessments of mass loading include the use of more sensitive analytical methods for pollutants of greatest concern, increased sampling frequency for large discharges, routine reporting of BDL results in their uncensored form, and comprehensive reporting of quality assurance data.