Shopping Center in Cincinnati, Ohio

Site Summary:

Chlorinated solvents were discovered in soil and ground water at a shopping center’s self-service dry cleaning operation. It was determined during the due diligence phase by a prospective buyer that contaminants had leached through the concrete floor slab and permeated the underlying soil and groundwater. After the property sale fell through, the owner of the shopping center wanted to remediate the contamination.

Geology and Hydrogeology

Site geology consists of a thin veneer of till and residuum over approximately 18 feet of interbedded shale and limestone bedrock. Ground water is perched at the top of the bedrock and flow direction is largely controlled by the bedrock fracture pattern. Contaminated ground water traveled through the fractures in three directions.

Ground Water Contamination

The hydraulic conductivity of the perched aquifer zone was approximately 10-4 cm/sec. The tetrachloroethene (PCE) concentrations in the ground water were as high as 13 ppm. The breakdown products trichloroethylene (TCE), 1,2-dichloroethylene (1,2-DCE), and vinyl chloride were also detected in lower concentrations (0.19, 0.120, 0.125 pm, respectively). The extent of ground water contamination covered approximately one acre.

Remediation Design

CL-Out was introduced through one-inch diameter piezometers installed using a direct push sampler. The small diameter injection points made it possible to install injection points inside the building without disrupting facility operations. Eight injection points were installed to treat the ground water plume.

The first CL-Out inoculation on August 18, 2000 was a high dose of five drums to establish the CL-Out microorganisms as the dominant microorganisms in the treatment zone. A lower dose inoculation of three drums was made after one and two months to maintain the CL-Out microbial activity.

Results

The monthly ground water sampling results from one monitoring well are summarized below. Over the course of three months, there was continuous decrease in the PCE concentration from 13.0 to 0.65 mg/L. While there was an apparent slight increase in the TCE and DCE concentrations, vinyl chloride was not detected after the first inoculation.

CL-Out bioremediation achieved the remediation goals for this site in less than three months, allowing the property to be marketed without the environmental stigma. The total remediation and monitoring costs were less than $50,000.