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Contamination has Dropped Around Bonneville Dam, Army Corps says by Scott Learn The Oregonian, January 20, 2011

Cleanup around Bradford Island at Bonneville Dam has reduced extraordinary levels of contamination there, but contaminants on land and water still exceed risk screening levels, the U.S. Army Corps of Engineers reported today.

The island historically served as a dump for electrical equipment and other potentially toxic debris. The Corps' Portland District dredged hot spots of contaminated sediment in 2002 and 2007, primarily to remove cancer-causing polychlorinated biphenyls, or PCBs.

PCB contamination in nearby Columbia River sediment, clams and crayfish dropped dramatically after the cleanups, a contractor's draft report for the Corps said.

Crayfish sampled in 2001 had PCB concentrations ranging as high 75,600 parts per billion, enough to be disposed of as hazardous waste. Samples taken from the same area in 2008 showed concentrations just under 17 parts per billion.

Trends are less clear for smallmouth bass living year-round near the dam. Samples taken in 2006 found contaminant concentrations as much as 26,000 times higher than what state officials consider safe for human consumption.

Smallmouth bass tissue has not been sampled since, the Corps said. URS, the agency's contractor, said the high contamination of the relatively long-lived fish likely occurred before the cleanups began, and future testing should show reduced levels.

The Corps will next consider the need for further cleanup work. Its draft report on the extent of the contamination is open for public comment through March 31.