DOE Proposes Natural Attenuation for Some Groundwater Contamination
WC Monitor
8/1/2014
The Department of Energy is proposing leaving some groundwater contamination near the Columbia River at F Reactor to naturally attenuate over 35-to-150 years. The plan is not sitting well with some agencies, though, including the Hanford Advisory Board. “This is the first reactor area along the river to be addressed with a final proposed plan,” said Dan Serres of Oregon-based group Columbia Riverkeeper. It could set a precedent for how cleanup is completed around the other eight plutonium production reactors at Hanford along the river, he said. “It is important to the board that these decisions are dependable, protective, defensible and well supported,” the advisory board said in advice to DOE and the Environmental Protection Agency, based on an early draft of the plan last year.
Most of the cleanup around F Reactor has been completed under interim cleanup decisions, leaving a final decision to be issued. The proposed cleanup plan on which the decision will be based covers not only the area around the defunct F Reactor, but also large areas of undeveloped land at Hanford for a total of 145 square miles. That includes the old Hanford and White Bluffs town sites and the LIGO observatory. DOE is proposing no direct action to clean the groundwater near F Reactor, but a reliance on a combination of natural processes, such as biodegradation, dispersion, sorption, dilution and radioactive decay. Natural attenuation would both protect human health and the environment and be cost effective, according to DOE’s proposed plan. The conditions do not currently present a risk to people, plants or animals, according to DOE. Until the contaminants dissipate, institutional controls would be used to prevent activities such as drilling wells.
Natural Attenuation Already Working, DOE Says
Because most cleanup has been completed around F Reactor, contamination there is no longer known to be contributing to the groundwater plume, according to DOE. Work started in the 1990s to remove 146 facilities and dig up contamination left from dumping contaminated liquid into the ground and burying contaminated equipment and debris. The DOE proposed plan says that 2 million tons of contaminated material have been removed. In addition to the contaminants found at most reactor sites, the F Reactor area also had contaminants left from a research farm there that used animals to study the effects of radiation.
The concentration of contaminants in the plumes is decreasing, showing that natural attenuation is working, according to the DOE proposed plan. In 150 years, strontium-90 from the experimental animal farm and also from reactor-related waste disposal would be reduced to drinking water standards. Nitrates from the animal farm would take 80 years to dissipate. Trichloroethene from waste sites that have been dug up would meet drinking water standards in 50 years. And chromium would be reduced over 35 years. Relying on natural attenuation plus monitoring, which would require more wells, and institutional controls is estimated to cost about $36 million.
Other Alternatives More Expensive
Other alternatives in the proposed plan would clean up contaminants faster, with the exception of strontium, but would be far more costly. A system to pump contaminated water from the entire 2,620-acre nitrate plume and treat it and the other contaminants forms the basis of the most aggressive proposal. The enhanced pump-and-treat system would take care of the nitrate in 25 years, the chromium in 10 years and the tricloroethene in 10 years. But it would come at a cost of $194 million. The Hanford Advisory Board has recommended that DOE pursue that proposal. It also wants a plan developed to address the strontium contamination, such as an apatite barrier that would trap the strontium and keep it from entering the river. An apatite barrier has been partially installed at N Reactor. “Allowing strontium 90 to decay is inappropriate when tested technology is available to address the plume,” the advisory board said.
Natural attenuation had been rejected many times by the Hanford Advisory Board, particularly so close to the river, Serres said. It is worth investing more money to protect the Columbia River, he said. DOE and EPA replied in a letter to the advisory board that monitored attenuation would be just as effective long-term as the more expensive enhanced pump-and-treat option. They also said that strontium-90 appears to be bound to the soil and is not migrating. Further efforts to bind it in the soil would not reduce the 150 years needed for decay. Columbia Riverkeeper also is concerned about DOE’s proposal to control some contamination within soil deeper than 15 feet by preventing irrigation and digging in those areas. Those institutional controls would be needed for as long as 264 years at one contaminated site. Removing and treating the contaminants at that site should be considered, according to the advisory board. The Hanford Advisory Board may make further recommendations at its September meeting. DOE is accepting comments at [email protected] until Aug. 11.
