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Data From Ongoing PCB Cleanup Below Bonneville
Shows Most Contamination Out of System

by Staff
Columbian Basin Bulletin, June 6, 2008

Preliminary data from analysis of sediment, clams and crayfish collected below the Columbia River's Bonneville Dam show few signs of PCBs (polychlorinated biphenyl), an indication that an ongoing cleanup/investigation of hazardous waste is on target.

"It means that we've gotten most of the PCBs out of the system," said project manager Mark Dasso of the U.S. Army Corps of Engineers, which operates the dam.

The Corps last fall completed the removal of 65 tons of sediment from a 0.83-acre area along the shoreline of Bradford Island, an oblong piece of land near the Oregon shore that anchors the north end of the hydro project's first power house and the south end of its spillway.

From the 1940s until about 1982, a landfill on Bradford Island's upstream tip was used to dispose of project waste materials like oil and grease, paint and solvents, scrap metals, mercury vapor lamps, cables and sand blast grit, according to the Corps. Some electrical transmission components like switchgear, insulators and possibly light ballasts were also placed in the landfill. Household waste came from a small community of homes used by construction workers and later project personnel until 1976.

The October effort involved suctioning 2.2 million gallons of water and sediment from the river bottom and filtering to remove contaminants. The resulting filtered water that was returned to the river was non-detectable for PCBs at five parts per trillion. The captured sediment that was taken to a licensed landfill was non-detectable for PCBs at 80 parts per billion, far lower than originally estimated.

The latest preliminary analysis honed in on clam, crayfish, sediment (18-19 samples of each) and water (five samples) collected in February and March in the forebay - above the spillway and powerhouse.

"I don't want to give you any numbers yet because the data is preliminary, but the samples were non-detectable for PCBs," Dasso said. The final analysis should be completed within 3-4 weeks.

The presence of PCBs in the in-water site has steadily declined since the electrical equipment, which included three capacitors, was removed in 2002 from "three distinct mounds of waste" discovered by accident two years earlier.

"I think that validates that we were still having a release (of PCBs), though small, from the equipment," Dasso said. Released PCBs normally attach to fine sediments, or get swept away. In this case they were found in coarser sand, possibly temporarily attached by oils.

The mounds were found in 2000 during a Corps underwater survey investigating potential seepage from the island landfill when divers "saw something shiny in the river." Sampling and analysis completed the following year showed PCB presence as high at 75,000 parts per billion in crayfish and 6,500 in clams.

Because of the high level of contamination at the in-water site, and the potential for PCBs to affect humans and fish and wildlife, the Corps "turned all of our attention there. It was more critical," Dasso said.

"The in-water site was of particular concern to us because of the potential effects on fish and wildlife" and human health, said Corps spokesman Scott Clemans.

"Getting the equipment out of the river was the main thing," though last year's sediment removal helped, Dasso said. Investigators still have some data gaps to fill, such as the collection of sculpin in the coming weeks to complete the in-river risk assessment of the food chain.

Because PCBs become attached to particles in the water, they eventually settle out and are buried in bottom sediments. Bottom-dwelling organisms ingest these PCB-contaminated sediments and pass them up into the food chain. The smallest aquatic organisms are eaten by successively larger predator fish which are then consumed by fish-eating mammals.

Bass, as an example, eat crayfish. And clam tissue has been found in crayfish.

PCBs have been detected in both fresh and saltwater fish in varying amounts depending on size, feeding grounds, position in the food chain, exposure, and fat content.

The Corps and Oregon Department of Environmental Quality in March announced the results of tests that show high concentrations of contamination in smallmouth bass caught in 2006 in the vicinity of Bradford Island.

Lab analysis showed concentrations of PCBs in the tissue of 19 smallmouth bass averaged 3,000 parts per billion, well above what DEQ considers to be a safe level -- about 1 part per billion. This risk is based on significant consumption of the fish over many years.

Investigators suspect that the PCB presence in the fish is the result of "legacy" contamination. The fish sampled were as old as 10, Dasso said. PCBs tend to accumulate over time in animal tissue.

Bass were chosen for sampling because they have a relatively small "home range," Dasso said. That means bass caught at Bradford Island likely spent most of their life there.

The Oregon Office of Environmental Public Health is reviewing the data in order to make a determination about fish advisories for the Bradford Island area. Until that fish advisory is finalized, OEPH recommends that bass fishers and consumers refer to the fish advisory for Portland Harbor where similar levels of PCBs have been found in fish. This advisory is available at

The Corps says that salmon and other fish species that migrate up rivers from the sea should not have been at risk to PCB contamination because of limited, if any, exposure.

More bass samples were collected in November and May but that analysis is not yet complete, Dasso said.

DEQ and the Corps will decide about monitoring PCB levels in fish and sediment in the river over the next several years to determine how much environmental improvement resulted from this dredging effort.

DEQ, the Corps and several other natural resource agencies and tribal representatives have been meeting on a regular basis over the past several years to work on investigation and cleanup of contamination on the island and in the river nearby.

Six groundwater monitoring wells have been installed this year, bring to 15 the total now in place at the site.

"The ultimate goal is to complete the sampling and analysis in 2008" for the in-river area, upland sites such as the landfill and "reference" areas, Clemans said. The sampling of upstream reference areas is to help evaluate what contaminants are being swept into the Bradford site.

Thus far there has been "no evidence that contaminants are seeping into the river" from the upland sites, Dasso said. The primary contaminants of interest that have been identified in the upland area soil and/or groundwater include metals (including butyltins), PCBs, polycyclic aromatic hydrocarbons (PAHs), and volatile organic compounds (VOCs), according to the September 2007 Remedial Investigation and Feasibility Study Management Plan for the Bradford Island site. The primary COIs in the sediment are metals, PCBs, and PAHs.

An exhaustive risk assessment of the data will be conducted next year to determine if additional cleanup is needed.

"It is impossible to estimate the total project costs at this time since the scope of cleanup actions is unknown," according to the management plan. "The total cost of the project to this point is approximately $7,000,000."

The Corps has been working with DEQ since 1998 to address environmental problems on Bradford Island. PCBs were used as coolants and lubricants in electrical equipment. Manufacture of PCBs stopped in the United States in 1977 because of evidence that PCBs build up in the environment and can result in harmful health effects to people and wildlife. The Environmental Protection Agency has determined that PCBs are probably carcinogenic to humans.

For more information about the Bradford Island cleanup can be found at the Corps' Portland District Web site at or the DEQ Web site at

For more information about the human health effects of PCBs, consult the public health assessment for Portland Harbor completed by Oregon's Environmental Health Assessment Program:

Data From Ongoing PCB Cleanup Below Bonneville Shows Most Contamination Out of System
Columbian Basin Bulletin, June 6, 2008

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