Publication Summary

A pilot study was undertaken to determine the concentrations of chlorinated pesticides, PCBs, and fecal coliform bacteria in stormwater from three storm drain outfalls in Pullman. The outfalls were sampled using grab samples during three winter storm events from December 2005 to April 2006.

PCBs, fecal coliform bacteria, and 4,4′-DDE were detected in all stormwater samples from Pullman storm drain outfalls. Dieldrin and heptachlor epoxide were detected in all but one stormwater sample. Many of the toxic compound detections were near the reporting limits. These detections and estimated loads will be considered in the upcoming TMDL (water cleanup plan) study.

Stormwater discharges from Phase II jurisdictions will soon be regulated by the Washington State Department of Ecology under the National Pollutant Discharge Elimination System (NPDES) program. Municipal stormwater loads of 303(d) listed toxic pollutants from Phase II stormwater systems have not been previously studied by Ecology.

A pilot study was undertaken to determine the concentrations of the 303(d) listed pollutants in municipal stormwater samples. The results may be used in developing Total Maximum Daily Loads for toxic compounds and fecal coliform bacteria in the South Fork Palouse River subwatershed. The city of Pullman and Washington State University are the only proposed Phase II entities in this watershed.

From December 2005 to April 2006, three storm drain outfalls were sampled for chlorinated pesticides, PCBs, fecal coliform bacteria, and conventional pollutants. 4,4′-DDE (a historical pesticide), PCBs, and fecal coliform bacteria were detected in all samples from the Pullman storm pipe outfalls. The pesticides dieldrin and heptachlor epoxide were detected in all but one sample.

Many of the toxic pollutant detections were near the reporting limits, and all detections are qualified as estimates due to the interfering "dirtiness" of the stormwater sample matrix. The conventional pollutant concentrations, including fecal coliform bacteria, were comparable to those found in the National Stormwater Quality Database, an ongoing study by Pitt and Maestre (2005).

The annual mass load of the toxic 303(d) listed pesticides, PCBs, and fecal coliforms were estimated from the measured concentrations using the Simple Method (Schueler, 1987). These stormwater concentrations may be used to (1) plan further studies to more accurately characterize stormwater sources, and (2) initiate actions to prevent stormwater sources of these chemicals in the storm drain systems.

Link to EIM data for User Study ID BRWA001