Abstract: Insitu Treatment of Barium Contaminated Soil; an Innovative Approach to RCRA Closure
URS Greiner, Inc., Columbus, Ohio
A chemical manufacturer in eastern Ohio was required through a consent order with the State of Ohio to complete a Resource Conservation and Recovery Act (RCRA) closure of three areas formerly used to store barium-containing materials. Two of the areas were used to store open topped drums of off specification material waiting reworking. The third area was an unlined decant pond formerly used to store spent barium hydrate liquors.
The closure process required sampling soils over a uniformly spaced grid in each of the three areas to define the horizontal and vertical extent of barium effected soils. The state initially required offsite background soil concentrations for barium to be defined, and soils in the three areas exceeding the background concentrations were to be removed for disposal as hazardous waste. The initial cost projections for this approach exceeded $1.5 million.
The chemical manufacturer could not bear the financial burden of the RCRA closure, so extensive negotiations were conducted with the State to secure approval for an alternate approach to closure. The agreed method for closure consisted of insitu treatment of effected soils using both cement and gypsum amendments top the soils to reduce the leaching potential of the barium. By reducing the leaching potential of the barium, the soils would be characterized as a solid waste rather than a hazardous waste. Bench scale testing was completed to determine the amount of soil amendment necessary to reduce the leaching potential of the barium. A soil amendment mixture of 6% cement and 4% gypsum (per weight basis) was determined effective. The cement would elevate the pH, limiting the potential for anion reduction, and the gypsum reacted to form barium sulfate which is non-leaching (insoluble).
The soils were treated in 6-inch lifts; treated soils were analyzed for leachability, for characterization as hazardous waste. If the analytical results were below hazardous characteristic levels, the soils were offloaded for disposal as a solid waste. This insitu treatment was completed for an approximate cost of $130,000, and the manufacturer was able to close the consent order with a "clean closure."
AAPG Search and Discovery Article #90930©1998 AAPG Eastern Section, Columbus, Ohio