Remediation Status: In active remediation

Why the technology was selected:
Bioremediation was selected as the groundwater remedy because PCE daughter products are present in groundwater and aquifer and geochemical conditions are favorable for reductive dechlorination: disolved oxygen concentrations range from 0.5 to 0.9 mg/l, Redox values range from -152 to -266 millivolts; Total organic carbon concentrations detected in groundwater range from 27 to 59 mg/l. Potassium lactate was chosen an an amendmenment because it is a relatively cheap carbon source.

Date implemented:
On site injection: Decemeber 14-28, 2005 Off site injection: January 4-13, 2006

Final remediation design:
A total of 10 injection wells were installed. Six of these wells (1.5-inch diameter PVC), were installed around the building that formerly housed the drycleaning operation using a direct push unit. Three wells were installed hydraulically upgradient of the facility and three wells were installed downgradient of the facility. A seventh 2-inch diameter injection well was later added downgradient of the facility. These wells were screened as follows: two wells 18-32 ft BLS, two wells 20-34 ft BLS, and three wells 12-29 ft BLS. Additionally, three injection wells (2-inch diameter PVC) were installed on the property immediately downgradient (across the street) of the former drycleaning facility. These wells were screened as follows: one well 18-32 ft BLS, two wells 19-34 ft BLS.

Results to date:
A total of 158,000 gallons of a 0.17% (w/w) potassium lactate solution (207 gallons or 3.8 drums of a 60% K-lactate solution) were injected in onsite injection wells over a 14 day period. Average injection flow rate was 1.2 gpm. 46,000 gallons of a 0.20% (w/w) potassium lactate solution (68 gallons or 1.2 drums of a 60% K-lactate solution),were injected in the four offsite injection wells. Average injection flow rate was 1.5 gpm. As of the February 15, 2008 monitoring event, PCE is no longer being detected. TCE has been largely converted to Cis 1,2-DCE (highest TCE concentration was 15.4 ug/L. The highest Cis 1,2-DCE concentration was 230 ug/l. After the injections, concentrations of Cis 1,2-DCE rose and have subequently declined. No vinyl chloride has yet been detected in groundwater at the site. An active soil gas survey was recently conducted. Of soil gas samples collected from five vapor extraction points, incluidng three installed beneatht the floor slab of the facility, only one soil gas sample had detectable concentrations of a contaminant: 1.4 mg/cubic meter.

Next Steps:
An addtional potassium lactate injection event is being considered.

Cost to Design and Implement:
Design: $13,300 Implementation: