Hanford workers cleaned 145,000 pounds of contaminants from the groundwater beneath the nuclear reservation during the past 12 months, the Department of Energy said Thursday.
The contaminants came from 2.2 billion gallons of groundwater — an amount that would fill enough water trucks lined bumper-to-bumper to stretch from Los Angeles to New York.
The contaminated groundwater was pumped out of the ground and treated at six Hanford plants, with cleaned water reinjected into the ground.
The plants include five along the Columbia River that remove hexavalent chromium. The chemical can cause cancer in humans and is particularly poisonous to young salmon, even in small amounts that meet drinking water standards.
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The sixth treatment plant, which is in central Hanford, is larger and more sophisticated. It can remove multiple contaminants from groundwater, including radioactive carbon tetrachloride and uranium.
An expansion of the plant allowed it to remove uranium from contaminated water throughout fiscal 2017.
Because there is a smaller mass of uranium in the groundwater than other contaminants, such as nitrates, contractor CH2M Hill Plateau Remediation Co., treated more water than in fiscal 2016, but removed less contamination by weight.
2.2 billion gallons of contaminated groundwater treated in fiscal 2017
18 billion gallons of contaminated groundwater treated in total
In fiscal 2016, Hanford plants treated 2.1 billion gallons of water to remove 180,000 pounds of contaminants.
Historically, an estimated 450 billion gallons of liquids were discharged to the soil, contaminating more than 100 square miles of groundwater. The water moves underground toward the Columbia River.
In recent years, Hanford officials have said that about 60 square miles of groundwater remain contaminated, but an updated figure for fiscal 2017 was not available Thursday.
The concentration of contaminants in the groundwater also has been dropping, according to CH2M.
With half of Hanford’s plants at least five years old, including the central Hanford 200 West Pump and Treat facility, major maintenance has been required to keep them running efficiently.
Some of the groundwater treatment plants along the river had new pumps installed during the past year, increasing treatment capacity at those plants by up to 300 gallons per minute.
Since treatment plants began operating in the mid-’90s, almost 18 billion gallons of contaminated groundwater has been cleaned and returned to the ground, according to DOE.