Work Underway to Upgrade Pump-and-Treat Plant to Address Uranium
WC Monitor
6/5/2015
Equipment is being installed in what’s already the most sophisticated groundwater treatment plant at Hanford to expand its capabilities to address another contaminant. By the end of the calendar year, the new system is scheduled to be tested and starting to remove uranium from water pumped from the ground in central Hanford, keeping the contaminant from eventually making its way to the Columbia River. The system, including some infrastructure, will cost about $6.2 million. The 200 West Pump and Treat Facility opened in 2012 already removes a variety of other contaminants from groundwater. Jon Peschong, Department of Energy deputy assistant manager for the Richland Operations Office, called it the crown jewel of the department’s groundwater treatment systems at a recent Hanford Advisory Board committee meeting. It can treat more types of contaminants than any other plant in the DOE complex of environmental cleanup sites. Microorganisms at the plant consume nitrates. An air stripping system removes carbon tetrachloride. The plant also can remove chromium and trichloroethene from groundwater.
The 17,500-square-foot radiological building on one end of the plant was built to remove radioactive contaminants from water. The ion exchange columns installed there initially treated water to remove technetium 99, but space was saved in the building to expand its capabilities with an additional set of ion exchange columns using resins that capture uranium. “All we had to do was put the skids in,” Peschong said. The ion exchange columns, a well-established technology similar to that used in home water softeners, were manufactured off site and trucked already assembled to central Hanford for installation.
Contamination Tied to U Plant
When Hanford was producing plutonium, more than 450 gallons of contaminated liquid was discharged into the soil in central Hanford. In the 1950s, U Plant was used to recover uranium from some Hanford waste, contaminating the ground there and eventually the groundwater beneath it with uranium. Both technetium and uranium move easily through the soil. Not only groundwater contaminated near U Plant, but also some “perched water” in central Hanford will be treated at the plant. About 2 million gallons of water have collected, or perched, in the soil above the water table in central Hanford. The water has moved downward through the soil until the movement slowed and it built up in a perched layer above the groundwater. It’s believed to be slowly entering the aquifer and contributing to the uranium contamination in the groundwater. The goal is to remove and treat as much of the perched water as possible before more reaches groundwater.
The project to expand treatment capabilities requires wells to be drilled near U Plant to retrieve the contaminated groundwater there and a double-walled above-ground pipeline to be installed to move the water to the treatment plant. It will run mostly along roadways, with curves to allow it to safely expand in the summer heat. A similar pipeline will be built from the plant in the 200 West Area running about eight miles to the 200 East Area, both in central Hanford. It will allow the perched water to be moved without trucking it and also has the potential for future use to move groundwater with other contaminants to the treatment plant. The contaminated water from the U Plant area will be treated at a rate of 150 gallons per minute. The rate for treating the perched water will be slower, not because of lack of capability at the plant but limitations in the ability to get that water out of the soil, Peschong said.
Facility Expected to Operate for 25 Years
The 200 West Pump and Treat Facility, built and operated around the clock by CH2M Hill Plateau Remediation Co., is expected to operate for 25 years to treat at least 25 billion gallons of contaminated water. Over the last seven months or so the plant has ramped up the amount of groundwater it has cleaned. It averaged about 2,000 gallons per minute of water treated over one recent month before slowing down for maintenance. No final decision has been made on cleanup of central Hanford groundwater. But the plant is so large and flexible that it could be the last water treatment plant that needs to be built in central Hanford, Peschong said.
