The Department of Energy has eliminated one potential source of mud contaminated with radioactive waste that swallows may be spreading at Hanford.
Besides the contaminated nest that stopped work at part of the Hanford vitrification plant Wednesday, other contaminated nests have been found this spring, said JD Dowell, DOE assistant manager for central Hanford and the river corridor.
Hanford workers tracked the possible source of at least some of the contaminated nests to the Liquid Effluent Retention Facility, after watching swallows moving back and forth from their nests to the facility.
The facility has three storage basins designed to hold about 23,000 gallons of waste water. Contaminated water is piped or trucked to the basin from several projects, including the 242-A Evaporator and groundwater cleanup projects. It's then routed to the Effluent Treatment Facility to be cleaned.
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The three basins are covered, but contaminated water was standing on top of the covers and enough dust had blown in that vegetation was growing.
With little water available in central Hanford, that may have attracted the swallows, Dowell said. In addition, they build their nests from mud.
The basin covers have been cleaned off and officials will see if that eliminates at least part of the problem, Dowell said.
There is no evidence that there is a risk to the public or any contamination spread off site from the center of the 586-square-mile nuclear reservation, he said.
Radioactive contamination occasionally is spread by wildlife at Hanford.
"When we find anything, we track it down to the source if we can," Dowell said.
This incident was unusual because no contamination from any source had been found before at the Hanford vitrification plant construction project.
The massive plant is being built to treat up to 56 million gallons of radioactive waste from the past production of plutonium for the nation's nuclear weapons program, but with treatment years away, none of the waste has been transferred to the site.
Because it is a "clean" site, workers there do not have the radiological training of workers elsewhere at the nuclear reservation, who are prepared to encounter radioactive contamination.
There is no specific evidence that the contamination found below a swallow's nest at the vit plant came from the Liquid Effluent Retention Facility, but it is being considered as a possibility by Hanford officials.
A small amount of contaminated dirt was found on the concrete floor of an open part of the plant's High Level Waste Facility, where swallows had built many mud nests under steel girders that had decking on top.
Swallows have nested there before, but in the past, no contamination had been found, said Suzanne Heaston, spokeswoman for Bechtel National.
An area of about 300 feet by 50 feet has been barricaded off in the area of the nests to keep workers safe, she said. Construction continued elsewhere at the building Thursday after work was stopped Wednesday.
In addition, three swallow nests have since been found in an outside truck bay of the Low Activity Waste Facility, she said. No contamination was found there, but the area has been cordoned off, she said.
Bechtel is working to hire a company to clean up the contamination, since Bechtel National does not work with radioactively contaminated material. The company also is expected to offer advice on managing the swallows, which are a protected species.
Bechtel's goal is to protect its workers, Heaston said.