Remediation Status: In groundwater monitoring

Why the technology was selected:
Bioremediation was chosen as the groundwater remedy because of the anerobic conditions existing in groundwater and the presence of PCE daughter products (TCE, Cis 1,2-DCE, Trans 1,2-DCE and vinyl chloride).

Date implemented:
July 2005

Results to date:
Contaminated soil was excavated to a depth of 7 ft below the parking lot over an area approximately 45 ft x 50 ft. Approximately 347 cubic yards (434 tons) of contaminated soil was excavated and disposed of offsite. Fifteen gallons of a 60%-purity bulk solution of potassium lactate was poured into the exposed groundwater in the excavation prior to backfilling of the excavation with clean fill. During the lastes monitoring event, conducted in June 2008, No PCE or TCE was detected in groundwater. Four monitor wells produced groundwater samples with contaminant concentrations exceeding MCLs: one well had a Cis 1,2-DCE concentration of 231 ug/l and three wells had vinyl chloride concentrations exceeding the MCL: ranging from 1.7 to 9.5 ug/l.

Next Steps:
Continue monitored natural attenuation.

Cost to Design and Implement:
$55,000 for all technologies

Why the technology was selected:
Excavation was chosen as the soil remedy because of the shallow water table and accessibility (source area was located under a parking lot).

Date implemented:
July 2005

Final remediation design:
During site assessment activities, a modified soil gas survey was conducted. Three vapor extraction wells were installed in 4-ft-deep hand-augererd borings. A 2-HP regenerative blower was used to extract soil gas at a flow rate of approximately 120 cfm, at a vacuum of 40 inches of water. Soil gas was extracted from each point for approximately 30 minutes. A soil gas sample from each extraction point was sent to a fixed laboratory for analysis. The highest contaminant concentration detected in soil gas samples was 46.4 milligrams per cubic meter in a sample collected near what was formerly the service alley behind the drycleaning facility. Conventional soil sampling was used to delineate the extent of soil contamination.

Results to date:
Contaminated soil was excavated to a depth of 7 ft below the parking lot over an area approximately 45 ft x 50 ft. Approximately 347 cubic yards (434 tons) of contaminated soil was excavated and disposed of offsite. Fifteen gallons of a 60%-purity bulk solution of potassium lactate was poured into the exposed groundwater in the excavation prior to backfilling of the excavation with clean fill. During the last monitoring event, conducted in June 2008, No PCE or TCE was detected in groundwater. Four monitor wells produced groundwater samples with contaminant concentrations exceeding MCLs: one well had a Cis 1,2-DCE concentration of 231 ug/l and three wells had vinyl chloride concentrations exceeding the MCL: ranging from 1.7 to 9.5 ug/l.

Next Steps:
Continue monitored natural attenuation.

Cost to Design and Implement:
$55,000 for all technologies