The Department of Energy and the Environmental Protection Agency are proposing a plan to clean up much of the radioactive and hazardous chemical ground water contamination over 35 years in a portion of central Hanford.
However, a lack of viable technology for certain contaminants will keep the ground water from being cleaned to drinking water standards for much longer than that.
DOE and EPA picked the 35-year plan as their preferred alternative after also considering 25- and 45-year plans.
The differences would include how aggressively contaminated water is pumped out of the ground and treated to remove carbon tetrachloride, uranium, nitrate, chromium and technetium 99. Cleaned water is then reinjected into the ground.
Hanford produced plutonium for the nation's nuclear weapons program during World War II and the Cold War, and liquid wastes were disposed to the ground in ditches, ponds, trenches and other in-ground structures.
The goal of DOE, EPA and the Washington State Department of Ecology is to clean ground water to potentially be used as a source of drinking water.
The contamination under consideration is in the southern portion of the 200 West Area of central Hanford. Much of the contamination is associated with past operation of U Plant, which extracted uranium from waste left from removing plutonium from irradiated fuel.
Hanford's largest and most sophisticated ground water treatment plant, the 200 West Ground Water Treatment Facility, recently began treating contaminated ground water in the 200 West Area to remove several radioactive and hazardous chemical pollutants.
A plan already is in place for contaminated ground water in the northern portion of the 200 West Area, which is associated mostly with the Plutonium Finishing Plant.
EPA also pushed to get a decision in place for the contamination in the southern portion of the 200 West Area to coincide with the start of operations of the new pump-and-treat plant, said Emerald Laija, an EPA scientist.
The 35-year plan would cost $319 million -- which is $15 million more than if much of the cleanup was stretched over 45 years and $23 million less than cleanup over 25 years. Contaminated water would be pumped up at a rate of 430 gallons per minute versus 530 gallons per minute for the 25-year plan or 330 gallons per minute for the 45-year plan.
The different costs would be based on infrastructure, including how many wells are added to pump water out of the ground and any changes at the new pump-and-treat plant, which was built to be expanded.
But no matter how aggressively contaminants are pumped out of the ground and treated, all of the carbon tetrachloride cannot be removed by that method, said John Morse, senior technical adviser for DOE's groundwater treatment program.
About 5 percent of the carbon tetrachloride, which was used as a solvent, would remain and naturally disperse and diffuse to return ground water to drinking water standards over an estimated 125 years.
The plume to the north associated with the Plutonium Finishing Plant, which also has carbon tetrachloride, also is expected to require 125 years to reach drinking water standards.
Radioactive iodine 129 is a tougher problem. No technology has been found by DOE to clean it from the ground water.
Instead, it is proposed to be controlled with hydraulic containment, Morse said. Water would be pumped into the ground to build an underground mound of water to prevent the plume contaminated with iodine 129 from migrating to the east.
An interim rather than a final decision will be made on the proposed plan, in part to allow continued work to find possible treatments for the iodine 129.
The public may comment on the proposed plan until Aug. 16 by emailing 200UP1PP@rl.gov or by mailing Tifany Nguyen, DOE Richland Operations Office, P.O. Box 550, A7-75, Richland, WA 99352. The proposed plan is posted on each day of the events calendar until Aug. 16 at www.hanford.gov.
-- Annette Cary: 582-1533; firstname.lastname@example.org