Deep soil mixing at the Paducah site will involve a large-diameter auger like this one.
Senior Advisor for Environmental Management David Huizenga (right) and Paducah Site Lead Reinhard Knerr look at a three-dimensional model of the Paducah site’s groundwater system. University of Kentucky College of Design students assembled the model for the Paducah Gaseous Diffusion Plant Citizens Advisory Board. The model was displayed at the April 18 Site-Specific Advisory Board Chairs Meeting in Paducah, where Huizenga spoke before taking his first tour of the Paducah site.
PADUCAH, Ky. – DOE, the U.S. Environmental Protection Agency (EPA) and Kentucky Department for Environmental Protection have reached a milestone toward the objective of reducing groundwater contamination at Paducah site.
The three agencies approved a Record of Decision (ROD) for the southwest plume sources. LATA Environmental Services of Kentucky, DOE’s cleanup contractor at Paducah, will start field work by summer 2013 to remediate sources contributing to a plume of contaminated groundwater in the southwestern portion of the site, as specified by the ROD. The areas of contamination do not extend beyond the plant boundaries and pose no threat to residents in the area.
A ROD is a publicly available document that explains which remedies were formally selected to clean up a contaminated area. The ROD is available here.
“The approval of this ROD is significant because it addresses three sources of groundwater contamination at the Paducah site,” said Reinhard Knerr, DOE Paducah Site Lead. “We’re very proud of this accomplishment and appreciate the cooperative effort with the regulatory agencies.”
DOE signed the ROD for the southwest plume on March 16, followed by EPA on March 20. Kentucky regulators then issued a letter of concurrence. The last ROD, signed in 2005, related to interim remedial action at a cleaning building that is the leading source of groundwater contamination at the site.
The new ROD relates to sources of trichloroethene (TCE), a hazardous substance in the ground at the site’s 2.2-acre former oil landfarm area and two locations near the C-720 Maintenance and Stores Building. Those source areas have resulted in contamination of the shallow gravel aquifer underlying the site and are located within the secured area.
TCE, a common industrial degreaser, was used at the site from the early 1950s until 1993. EPA regulates TCE in drinking water to protect public health. EPA has set an enforceable standard, called a maximum contaminant level, of 0.005 milligrams per liter in drinking water. However, potentially impacted groundwater at the Paducah site is not used to supply drinking water.
The remedy for the landfarm area is deep soil mixing, which blends material such as reactive iron particles with the soil to chemically break down organic contaminants into nontoxic end products.
Starting no later than June 2013, workers will use heavy machinery to drill into the ground and inject reactive iron to a depth of about 50 feet.
Waste oils containing TCE were biodegraded at the landfarm from 1973 to 1979, using lime and fertilizer.
Additional testing this summer will determine whether bioremediation or long-term monitoring will be implemented for the other two sites, northeast and southeast of the Maintenance and Stores Building. Both have TCE contamination in the upper 50 feet of soil.
Spills from routine equipment cleaning and rinsing are the suspected source of the contamination northeast of the maintenance building. TCE may have been discharged from inside the building through storm drains to the southeastern site, which houses instrument maintenance facilities and maintenance supply storage. Other sources may have been spills or leaks on the loading dock or parking lot southeast of the building.
If bioremediation is the remedy, implementation will start in 2014. Bioremediation uses microorganisms or their enzymes to aid in the degradation or breakdown of contaminants into nontoxic end products.
The southwest plume, one of three major contaminated groundwater plumes at the site, is generally confined to the southwestern part of the site’s fenced area.