By SUE RYAN
News staff writer
October 15, 2007

A steady thudding sound and disembodied voice can be heard just offshore of Bradford Island near Bonneville Dam.

The sounds are not the accompanying soundtrack to a horror flick but the work of underwater divers as they vacuum the Columbia’s riverbed and talk over a speaker to their crew above water.

The contract crew from Huang Associates and Co. from Elk Grove, Calif., began work Oct. 1. They are working under a $1.9 million contract with the U.S. Army Corps of Engineers and are expected to be finished by Nov. 15.

To work outside of the normal window of allowed in-water work, the agency collaborated with several other federal agencies that oversee fisheries management in the Columbia River.

“I don’t know of another project in my 20 years where we have gotten the cooperation we have on this project to work outside of the window,” said Mark Dasso, the Army Corps project manager.

Generally in-water work is only allowed between Dec. 1 and Feb. 28, which is outside of the time span fish migrate through the Columbia River.

While a two-year study is still underway to evaluate the extent of the remaining contamination on the island and in the river, the Corps wanted to be proactive in removing what it already knew to be polychlorinated biphenyl (PCB) laced sediments.

The contamination is concentrated in the river bottom sediments on the north side of Bradford Island and includes a .83-acre area of “hot spots.”

The Corps took the action after the recommendation of a citizens’ advisory group, which included Rachael Pecore of Columbia Riverkeeper and Cascade Locks City Councilor Darrell Driver.

The contamination on Bradford Island came from several sources, which the Corps has been compiling and studying. They have identified five upland sites: an old landfill, old pistol range, drum storage area, sandblasting area and slope where light bulbs were dumped.

Many of the sites remain from a time when government workers were housed on upper Bradford Island. The in-water site, on the lower island, is the target of the cleanup efforts. Dasso said the Corps discovered three distinct piles of electrical capacitors dumped in the water that came from a former powerhouse replacement.

PCBs are colorless, odorless and tasteless chemicals that were widely used in electrical equipment such as transformers and capacitors before their production was banned in 1976.

The species most at risk from the sediment contamination are clams, smallmouth bass and crayfish.

The Corps removed the equipment in 2002 and sampled the sediments in 2003. The cleanup on the entire project is expected to last at least two more years.

For now, as shown in an underwater video, the divers will nudge the hose along the bottom inch by inch. A cylindrical grated cap barrel sits over the top of the hose to prevent it from clogging with clam shells. To prevent the contaminated sediment from flowing downstream, divers are working slowly and feeding sediment directly into the hose.

“There was a concern that the cleanup might send material downstream but this action should be taking care of the issue,” Dasso said. “We’re measuring turbidity downstream and those measurements have shown no changes so far.”