PROJECT SUMMARY
WHAT:
In situ Enhanced Bioremediation
WHO:
Linda Cummings, DVM, PhD
David Hawley, P.E.
WHERE:
Former Dry Cleaners Lafayette, LA
WHEN:
2014-present
BACKGROUND
upplemental in situ enhanced bioremediation (ISEB) was implemented at a former dry cleaning store site to address the residual chlorinated constituent concentrations in groundwater in a previously treated source area, as well as, three previously untreated peripheral areas. Based on the results of the historical site investigations, the originally treated source area had been identified as a 90-ft by 150-ft area located at the rear of store, where solvents were believed to have been delivered and spilled. The original 2008 ISEB at this site included the co-injection of a carbon source in the form of emulsified vegetable oil (EO) and a commercially available Dehalococcoides (Dhc) species microbial culture. The remedial strategy for the site targeted an intermediate depth of 40 to 50 feet bgs, and a deeper depth of 50 to 65 feet bgs in select source area locations.
FINDINGS
ost ISEB concentrations of PCE and TCE in the former source area wells had decreased by one to three orders of magnitude as compared to the baseline monitoring results of December 2006. However, the 2014 concentrations of Dhc gene copies/liter in the source area wells were in the low to moderate range with a decreasing trend. In addition, the total organic carbon (TOC) concentrations measured in these wells ranged from <1 to 129 mg/L, which were significantly less than those present immediately following the initial 2008 injection activities (maximum of 2,160 mg/L). These findings suggestedthat site conditions were no longer optimal for high rates of dechlorination, and that the supplementation of electron donor substrate and Dhc were required to optimize the bioremediation.
RESOLUTION
ptimization of site conditions was necessary for the continued and complete dechlorination of the remaining COC in order to achieve site closure. The objectives of the supplemental remediation were to:
- replenish electron donor substrate and increase Dhc counts within the previously treated source area, and
- implement ISEB in three previously untreated peripheral areas showing COC concentrations above remedial goals.
Groundwater monitoring conducted approximately 3 months after supplemental ISEB implementation revealed that COC groundwater concentrations in the treated peripheral areas had decreased to non-detect or below remedial goals. In the source area, groundwater concentrations were non-detect and/or below remedial goals in two monitor wells and relatively unchanged in two other wells. Semi-annual groundwater monitoring is ongoing at this site.
PROJECT SUMMARY
WHAT:
Title V Air Permitting And Compliance
WHO:
Shawn Pitchett
WHERE:
Polymers Facility in Southwest Louisiana
WHEN:
2015- Present
BACKGROUND
upplemental in situ enhanced bioremediation (ISEB) was implemented at a former dry cleaning store site to address the residual chlorinated constituent concentrations in groundwater in a previously treated source area, as well as, three previously untreated peripheral areas. Based on the results of the historical site investigations, the originally treated source area had been identified as a 90-ft by 150-ft area located at the rear of store, where solvents were believed to have been delivered and spilled. The original 2008 ISEB at this site included the co-injection of a carbon source in the form of emulsified vegetable oil (EO) and a commercially available Dehalococcoides (Dhc) species microbial culture. The remedial strategy for the site targeted an intermediate depth of 40 to 50 feet bgs, and a deeper depth of 50 to 65 feet bgs in select source area locations.
FINDINGS
ost ISEB concentrations of PCE and TCE in the former source area wells had decreased by one to three orders of magnitude as compared to the baseline monitoring results of December 2006. However, the 2014 concentrations of Dhc gene copies/liter in the source area wells were in the low to moderate range with a decreasing trend. In addition, the total organic carbon (TOC) concentrations measured in these wells ranged from <1 to 129 mg/L, which were significantly less than those present immediately following the initial 2008 injection activities (maximum of 2,160 mg/L). These findings suggestedthat site conditions were no longer optimal for high rates of dechlorination, and that the supplementation of electron donor substrate and Dhc were required to optimize the bioremediation.
RESOLUTION
ptimization of site conditions was necessary for the continued and complete dechlorination of the remaining COC in order to achieve site closure. The objectives of the supplemental remediation were to:
- replenish electron donor substrate and increase Dhc counts within the previously treated source area, and
- implement ISEB in three previously untreated peripheral areas showing COC concentrations above remedial goals.
Groundwater monitoring conducted approximately 3 months after supplemental ISEB implementation revealed that COC groundwater concentrations in the treated peripheral areas had decreased to non-detect or below remedial goals. In the source area, groundwater concentrations were non-detect and/or below remedial goals in two monitor wells and relatively unchanged in two other wells. Semi-annual groundwater monitoring is ongoing at this site.