Publication Summary

A stormwater runoff study was conducted at Pacific Woodtreating Corporation (PWT) in Ridgefield. The purpose of the study was to gather information concerning possible contamination of rainfall runoff from the PWT site. Stormwater runoff was sampled on three occasions. Sediments from Lake River and two on-site catch basins were analyzed.

A stormwater runoff study was conducted at Pacific Woodtreating Corporation (PWT) in Ridgefield. The purpose of the study was to gather information concerning possible contamination of rainfall runoff from the PWT site. Stormwater runoff was sampled on three occasions. Sediments from Lake River and two on-site catch basins were analyzed. The study revealed pentachlorophenol (PCP) and polynuclear aromatic hydrocarbons. (PNA) are present in PWT surface runoff, on-site sediment catch basins and some near-field sediments. Runoff concentrations of PCP may be the main cause of the high toxicity measured by three bioassays, although PNA′s and metals may have contributed. The on-site catch basin sediments were highly contaminated with PNA′s, while the sediment sample from Lake River at Outfall #3 contained more modest amounts. Sediment bioassay toxicity appeared to be closely linked to sediment PNA concentrations. Catch basin sediments exceeded Washington′s designation level for PNA′s as a dangerous waste, and had high concentrations of several metals. Several recommendations were made concerning further definition of contaminated streams, management practices, and bioassay and chemical monitoring.