One of the Hanford Site’s longest-running cleanup projects has been completed, leaving the Columbia River better protected from contamination from carbon tetrachloride. The Environmental Protection Agency has agreed that a plume of the carcinogenic chemical in central Hanford has been cleaned up to legal standards after more than three years of monitoring to ensure that levels of carbon tetrachloride did not rebound after active cleanup stopped. “This constitutes a successful end to a project that began 25 years ago, one of the longest continuously running cleanup projects on the Hanford Site, and demonstrates the persistence of our workers and their dedication to the goal of Hanford cleanup,” said Michael Cline, director of the Department of Energy Richland Operations Office’s soil and groundwater branch.
A technology used in the petroleum industry was successfully demonstrated in 1990 at the Department of Energy site and then put into full-scale service at the carbon tetrachloride plume near the Plutonium Finishing Plant in central Hanford. At the time Hanford officials said it was the largest known remediation project to use vapor extraction technology more commonly employed to remove gasoline from soil surrounding leaking underground storage tanks at gas stations.
At Hanford a vacuum pump was attached to monitoring wells to induce air flow in the soil. It caused the carbon tetrachloride to vaporize. Over the years 90 tons of carbon tetrachloride was trapped in activated carbon, with the filters in recent years disposed of at Hanford’s Environmental Restoration Disposal Facility. Roughly 60 to 70 percent of the carbon tetrachloride removed from the soil was captured in the first five years of operation of the vapor extraction system, said Karen Wiemelt, vice president of soil and groundwater cleanup for cleanup contractor CH2M Hill Plateau Remediation Co. The project’s full cost was not immediately available, but $9.6 million was spent from 2002 to 2015.
The Plutonium Finishing Plant used carbon tetrachloride from 1955 to 1973 as part of the process to recover plutonium from the facility’s waste. It was discharged with other chemicals into the soil in trenches near the plant. The chemical contaminated soil at levels high enough to be a concern down to about 200 feet deep and in an area of about three-quarters of a mile. Some of it reached the groundwater, spreading to contaminate about 5 square miles of groundwater. Hanford is using the 200 West Pump and Treat Facility to address the groundwater contamination. Removing the source of contamination in the soil will prevent further groundwater contamination, Hanford officials said.
