Sustainable Technologies Lead to Savings for Groundwater, Soil Cleanup at SRS

A soil vapor extraction unit is used to remove contaminant mass from the soil and prevent further impacts to groundwater at the Savannah River Site.

AIKEN, S.C. - U.S. Department of Energy (DOE) Office of Environmental Management (EM) crews successfully completed cleanup of pits and trenches used during the Cold War era to burn and bury accumulated waste from the site's A Area that had contaminated the surrounding soil and groundwater.

To clean up the contaminated soil and groundwater, crews with EM contractor Savannah River Nuclear Solutions (SRNS) completed remedial actions identified by a team consisting of members from DOE, the U.S. Environmental Protection Agency and South Carolina Department of Environmental Services. Workers placed a vegetative soil cover over the areas to reduce precipitation from moving contamination deeper into the subsurface.

Crews then used a process known as soil vapor extraction (SVE) in two phases to remove the contaminant mass from the soil and prevent further impacts to groundwater. In the first phase, known as active SVE, a high-energy vacuum unit removed contaminants. In this process, wells deep underground connected to an SVE machine at the surface that applied a vacuum to the wells and extracted vapors containing volatile organic compounds. The vapors were treated and released into the atmosphere, where they typically vaporize into the air.

In the second phase, passive SVE drew from natural resources, such as pumps powered by solar panels, to continue removing contamination.

"The phased SVE approach allows for optimizing the removal of contaminant mass from the subsurface while reducing cost for operations and maintenance," says Joao Cardoso-Neto, project task team lead. "During active SVE operation, the direct cost of operations and maintenance averaged approximately $150,000 per year, which was reduced to approximately $60,000 per year during low-energy and passive SVE operation."

MicroBlowers and BaroBalls, pictured, prove to be a sustainable and cost-effective method for groundwater remediation at the Savannah River Site.

Sustainable green technologies, including solar-powered SVE units such as MicroBlowers, are an example of passive cleanup. These units are designed to generate a vacuum that exhausts contaminants from designated wells. Each unit requires only 20 to 40 watts of power, easily produced by a small solar panel. Another passive SVE technology, called BaroBalls, makes it possible to pump contaminants from the subsurface by harnessing natural changes in barometric pressure.

Cumulatively, these technologies are proving to be a cost-efficient means of reducing risk to human health and the environment, and they're shortening the time needed for site cleanup. From 2001 to 2017, active SVE systems removed over 300 pounds of chlorinated solvents, and from 2004 to 2023, the MicroBlowers and BaroBalls removed approximately 150 pounds of chlorinated solvents.

Declining contaminant concentrations indicate the SVE system is effectively meeting cleanup objectives.

"With the MicroBlowers and BaroBalls getting the job done, the active SVE unit is no longer needed and can be permanently removed from service," says Eric Schiefer, an SRNS engineer with the project team.

The active SVE system was dismantled and removed from the site this past spring after it was permanently shut down in 2018. Passive SVE continues to operate. However, based on diminishing contaminant mass removal rates, the project team conducted a series of soil samples. Sampling was performed to evaluate the effectiveness of the low-energy, passive SVE units and to determine if cleanup goals had been achieved. Results from the soil sampling should be able to provide evidence that the low-energy, passive SVE system has achieved all cleanup goals and can also be permanently shut down.

-Contributor: Fallan Flatow