AIKEN. S.C. – EM is using 760 tons of iron filings recycled from the automotive industry to treat groundwater contaminated by solvents in a section of an aquifer beneath the Savannah River Site (SRS).
The filings, which are ground-up iron parts from automotive engines, will be mixed with a food-grade, starch-like material and injected into 22 wells, each 12 feet apart. The high-pressure injection creates fractures in the subsurface rock, creating space to be filled by the mixture. Upon completion, a four-inch-thick, water-permeable wall consisting of iron filings will extend to its deepest point approximately 135 feet below the earth's surface.
Groundwater will flow through the 264-foot-long, 23,000-square-foot metal wall, which neutralizes the solvents.
“The contaminated water cascades down through the filings, significantly increasing the amount of contact with the iron. The interaction with the iron breaks down the structure of the contaminants, becoming harmless,” said Philip Prater, senior physical scientist with the Savannah River Operations Office. “And this system is designed to work for decades with little maintenance, as it has in other parts of the country.”
According to Prater, the remedial technology EM and SRS prime contractor Savannah River Nuclear Solutions (SRNS) are deploying is innovative because it does not involve use of a trench, and it can be installed at greater depths than permeable reactive barriers built at the site in the past. This technology also allows for precision placement, enabling SRS to intercept the contaminated groundwater plume in a narrow zone as it travels along an old, subsurface stream bed channel.
"This is the first time we have experimented with this approach using a subsurface wall to capture and neutralize solvents,” said Mark Amidon, a scientist at EM’s Savannah River National Laboratory. “We are confident that our goals will be fully achieved related to this remarkably cost-effective project at the Savannah River Site’s P Area."
From 1954 to 1984, the site's P Reactor produced tritium and plutonium in support of the nation's Cold War nuclear deterrent. Solvents used at that reactor and waste sites across SRS seeped into the subsurface over time.
"This highly efficient environmental cleanup technology is another asset within the arsenal of environmental restoration tools assembled for use across SRS," said Seth Miller, the SRNS project manager for the groundwater cleanup.
The water-permeable wall is scheduled for completion in November this year.