The Department of Energy and CH2M Hill Plateau Remediation Co. have exceeded DOE's fiscal 2013 goal to remove 500 pounds of hexavalent chromium from groundwater six months ahead of schedule, they announced in a press release this week.
However, the goal was set at half of last year's work, when more than 1,000 pounds of chromium were removed from contaminated groundwater along the Columbia River.
The five pump and treat systems along the river have helped DOE double the amount of chromium removed from groundwater each year, according to the announcement. The systems pump up contaminated water from a system of wells, treat it and then return it to the ground.
Two of the systems, one near the D and DR reactors and one near H Reactor, began operating in 2011. They both use a new resin that can hold up to 15 times as much chromium as the resin that was being used at other Hanford pump and treat systems. The resin also strips more of the chromium out of the water.
The previous resin could absorb no more chromium after a month of use, requiring about 100 change-outs total among the tanks in a pump and treat plant in a year.
The new resin requires less down time, allowing more water to be treated. The other pump and treat systems on the Columbia River have since been converted to also use the new resin, contributing to the increased efficiency in removing chromium.
DOE set a more modest goal for the total amount of chromium to be removed this fiscal year because the amount of contamination in the groundwater decreases as cleanup progresses, said DOE spokesman Geoff Tyree.
"Based on forecasting seen at the end of the year for contaminant removal, it was a good goal," he said. "The overall goal of restoring groundwater to beneficial uses is a good goal for the environment and protecting public health."
The primary concern about chromium-contaminated groundwater near the Columbia River is risk to aquatic species that live among the gravel below the water where Hanford groundwater enters the river. Fish are more sensitive than people to chromium.
"Every amount of contamination removed is significant to the cleanup mission," said Bob Popielarczyk, CH2M Hill vice president of groundwater remediation, in a statement. "Just a small amount of hexavalent chromium with a weight equivalent to one grain of salt could contaminate eight gallons of water above aquatic standards, which is more stringent than drinking water standard."
Chromium plumes cover about five square miles along the Columbia River. More than 5,700 pounds of chromium have been removed from groundwater.