Wednesday, December 11, 2019
Dec. 11, 2019

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Hanford boosts contaminated groundwater cleanup to protect the Columbia River

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Published: December 2, 2019, 8:07pm

The Hanford nuclear reservation is expanding its capacity to clean chemical and radioactive contamination from the groundwater.

“That will reduce the time needed to clean up the groundwater,” said Mike Cline, the Department of Energy project director for cleanup of groundwater at Hanford. “The more water we can treat, the quicker we can complete total cleanup.”

The 580-square-mile nuclear reservation sits over about 65 square miles of groundwater contaminated by past practices at the site, such as dumping contaminated liquids into the soil.

Work is being done to pump the contaminated groundwater up through wells, remove the contaminants at six “pump and treat plants” and then inject the cleaned water back into the ground.

The water moves underground toward the Columbia River, so treating the groundwater keeps contamination out of the river and protects communities downstream.

Hanford has had success with its five pump and treat plants near the Columbia River, substantially reducing the size and amount of pollutants in the contaminated groundwater plumes associated with reactors that used to irradiate uranium fuel to produce plutonium for the nation’s nuclear weapons program.

While treatment plants by the river continue to operate, DOE is turning its focus to increase treatment in the center of Hanford where the irradiated fuel was chemically processed to remove the plutonium.

The most sophisticated groundwater treatment plant at the site, the 200 West Pump and Treat Facility, was opened in 2012.

The plants along the river remove hexavalent chromium, a corrosion inhibitor added to reactor cooling water. It can cause cancer in humans and is harmful to salmon and other aquatic life, even at levels that meet drinking water standards.

The 200 West Pump and Treat Facility in the center of Hanford removes not just chromium, but uses different treatment technologies to remove the radioactive contaminants uranium and technetium 99, plus the chemicals nitrogen, carbon tetrachloride and trichloroethene.

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A year ago, the plant had 2,000 gallons of contaminated water a minute, and that was increased to 2,500 gallons per minute by this fall. An additional line was installed to let some of the least contaminated groundwater bypass some of the treatment processes.

Now DOE and its contractor, Jacobs-owned CH2M Hill Plateau Remediation Co., plan to increase treatment capacity by 50 percent to 3,750 gallons per minute.

That’s possible because of the plant’s success in removing nitrates from central Hanford groundwater, which are particularly harmful to babies and pregnant women in drinking water.

Last year, 82 tons of the 85 tons of contaminants removed at all Hanford groundwater treatment plants were nitrates in the center of the site.

“Nitrate is really no longer an issue,” Cline said.

The reduced amount of nitrates in the groundwater will be allowed to dissipate rather than being removed by a treatment plant.

That will allow capacity to be increased at the plant to remove uranium and technetium 99 with the plant’s ion exchange systems and to remove organics, including carbon trichloroethene and carbon tetrachloride, using air stripping.

Since 2008, all six groundwater treatment plants at Hanford together have cleaned about 20 billion gallons of water, according to DOE.

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