AIKEN, S.C. – In the past 10 years, EM and the Savannah River Site (SRS) management and operations contractor have increased the effectiveness of groundwater cleanup and saved millions of dollars through passive, energy-efficient treatment technology.
Since 2008, more than 60,000 pounds of nonradioactive contaminants have been removed from the groundwater beneath SRS at a cost savings of more than $5.5 million, adding to the total of 1.6 million pounds of total nonradioactive material removed beneath SRS since the initiation of site groundwater cleanup in the early 1980s.
EM and Savannah River Nuclear Solutions (SRNS) have improved and expanded technologies to capture and manage radioactive contaminants in the subsurface. They use underground barriers that result in a cost avoidance of 90 percent, as the annual cost has declined from about $12 million to $1 million. This was achieved by coupling the underground barriers with periodic injections of special materials to adjust groundwater chemistry and promote natural conditions where contaminants adhere to underground sediments.
“The cleanup of the groundwater at SRS is one of our most important missions,” SRNS President and CEO Stuart MacVean said. “We’ve been able to do more cleanup for less money and we’ve done it safely. This is a testament to both our partnership with DOE and our commitment to continuous improvement.”
SRS is working with the Savannah River National Laboratory to implement more innovative, passive technologies requiring little or no electricity instead of active, highly mechanized systems. All but one of the active remedial systems are projected to be phased out within five years.
“Early active groundwater cleanup projects at SRS concentrated on using more aggressive methods to separate and remove the contaminants from tens of millions of gallons of groundwater,” SRNS Area Cleanup Projects Project Manager Mike Griffith said. “Examples of active technologies include steam injection and air stripping, requiring the power of large electric pumps, support facilities, and monitoring equipment.”
Those pump-and-treat systems effectively removed a high percentage of subsurface chemicals. However, passive remediation technology has been determined to be the more cost-effective means to complete the cleanup.
The primary advantage of passive systems are their ability to harness natural properties to protect, manage, and remediate groundwater.
Solar-powered soil vapor extraction units known as MicroBlowers 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.
Griffith explained that a single MicroBlower removed 234 pounds of volatile organic compounds from chemically contaminated subsurface at SRS during a 10-month test. He added that SRNS would eventually like to rely primarily on a technology called BaroBalls, which operate completely on natural changes in barometric pressure to pump contaminants from the subsurface.
“No energy is used and excellent results are obtained,” Griffith said.
Bioremediation relies on feeding naturally occurring microbes found in soil to accelerate cleanup. The microbes eat contaminants covered with vegetable oil injected into wells.
These technologies also are shortening the time needed for cleanup.
“Overall, we currently have 39 groundwater remediation systems operating at SRS,” said Karen Adams with the DOE Infrastructure & Area Completion Division. “It’s a carefully researched, planned, and comprehensive approach to environmental remediation at SRS we’d like to share across the DOE complex.”