MIAMISBURG, Ohio – A novel approach to groundwater cleanup by EM’s Savannah River National Laboratory (SRNL) is expected to cut the timeline in half for treating a contaminated plume at the Mound Site and could save more than $6 million over the project life.

   EM completed cleanup at Mound in 2010 and turned the site over to the DOE Office of Legacy Management (LM). A pump-and-treat system remained active there to address a plume of chlorinated volatile organic compounds (VOCs) under the site of a former mixed-waste landfill, with plans to operate the system through 2040.

   But researchers at SRNL believe an innovative technology could significantly reduce the time and cost to treat the plume through enhanced attenuation, an approach they developed and successfully used at several locations at the Savannah River Site.  

   After being approached by LM, SRNL tested the alternative system at Mound last year, turning off the pump-and-treat system and monitoring the effectiveness of enhanced attenuation. 

   A year later, the results are in and the plume has decreased in size and mass, and SRNL projects the concentrations of the VOCs will be below regulatory limits in five to 10 years.

   SRNL met quarterly with the Ohio Environmental Protection Agency (EPA) to explain the alternative approach and achieve the agency’s concurrence. The Ohio EPA has approved moving forward with it, and pending further approval by the regulators, LM will remove the existing pump-and-treat system. 

   “The enhanced attenuation approach has significantly accelerated the progress in cleaning up this plume,” SRNL Director Terry Michalske said. “This is a great example of our core mission at SRNL, developing and deploying approaches like this one to work in the complex to solve problems, increase efficiency and save money.” 

   Enhanced attenuation uses two forms of oil — emulsified oil that goes into the water and neat oil that floats on top of the water — injected into the aquifer to help remove the contaminants from the water. 

   “As the water table goes up and down, it sequesters the VOCs because they would rather be in the oil than in the water,” said SRNL researcher Brian Looney. “The oil also stimulates the subsurface bacteria and accelerates contaminant degradation rates.”

   SRNL researchers believe other EM sites where declining concentrations of VOCs reduce the effectiveness and efficiency of the active pump-and-treat system are good candidates for enhanced attenuation. The lab is continuing to work with DOE on future deployment.

   “Enhanced attenuation can really be a bridge between the efforts to actively clean up the source of groundwater contamination and traditional monitored natural attenuation,” Looney said.