Remediation Status: In groundwater monitoring

Why the technology was selected:
In-situ bio-augmentation followed by monitored natural attenuation was chosen because it provided for the degradation of the COCs through cometabolism with minimal disruption to on-going site activities. The groundwater plume is generally centered on-site beneath the dry cleaner facility. Therefore, excavation was not a viable option.

Date implemented:
May 2011

Final remediation design:
FY2011: in-sito bio-augmentation follwed by MNA. 300 gallons of facultative bacteria and nutrients mixed with clean water were injected under pressure into the shallow GWBU. The bioremediation product used was Cl-Out. The injections were performed through 25 temporary injection points placed around the periphery of the facility in the areas of highest concentrations. The injection points were advanced using direct push methods on a grid of approximately 20 feet.

FY2012: Additiional in-situ bio-augmentation events were completed. Cl-Out was injected int o the shallow GWBU through temporary injection points advanced by a direct push rig.

Results to date:
Reductions of 30 to 90 percent PCE concentrations have occured. Analytical results of the current groundwater monitoring and sampling show decreasing concentrations of COCs across the source area within the first GWBU. The decreasing trends can be attributed to a combination of in-situ bio-augmentation events completed at the site in FYs 2011 and 2012 and the on-going natural attentuation response actions.
As a result of the degradation of PCE, concentrations of the daughter products (TCE and cis-1,2-DCE) have increased in some of the monitoring wells. Concentrations of VC remain below the laboratory detection limits in first GWBU monitoring wells indicationg that complete dechlorination of the COCs are occuring.
Monitoring wells in the second GWBU indicate that present COC levels do not exceed the class 3 groundwater ingestion pathway PCLS. Therefore, a response action is not required at this time.

Next Steps:
Continued response action with an emphasis on maintaining dissolved oxygen level above 1.0 mg/L. The increase in biological activity in the plume source area has decreased dissolved oxygen to concentrations generally less than 1.0 mg/L, which indicate anaerobic conditions. As the groundwater becomes anaerobic, the CI-Out bacteria will begin to die as the naturally occuring bacteria begin to dominate, resulting in an incomplete degredation pathway and the accumulation of PCE daughter products.

Cost to Design and Implement:
$102,758.52

Why the technology was selected:
In-situ bio-augmentation followed by monitored natural attenuation was chosen because it provided for the degradation of the COCs through cometabolism with minimal disruption to on-going site activities. The groundwater plume is generally centered on-site beneath the dry cleaner facility. Therefore, excavation was not a viable option.

Date implemented:
May 2011

Final remediation design:
FY2011: in-sito bio-augmentation follwed by MNA. 300 gallons of facultative bacteria and nutrients mixed with clean water were injected under pressure into the shallow GWBU. The bioremediation product used was Cl-Out. The injections were performed through 25 temporary injection points placed around the periphery of the facility in the areas of highest concentrations. The injection points were advanced using direct push methods on a grid of approximately 20 feet.

FY2012: Additiional in-situ bio-augmentation events were completed. Cl-Out was injected int o the shallow GWBU through temporary injection points advanced by a direct push rig.

Results to date:
Reductions of 30 to 90 percent PCE concentrations have occured. Analytical results of the current groundwater monitoring and sampling show decreasing concentrations of COCs across the source area within the first GWBU. The decreasing trends can be attributed to a combination of in-situ bio-augmentation events completed at the site in FYs 2011 and 2012 and the on-going natural attentuation response actions.
As a result of the degradation of PCE, concentrations of the daughter products (TCE and cis-1,2-DCE) have increased in some of the monitoring wells. Concentrations of VC remain below the laboratory detection limits in first GWBU monitoring wells indicationg that complete dechlorination of the COCs are occuring.
Monitoring wells in the second GWBU indicate that present COC levels do not exceed the class 3 groundwater ingestion pathway PCLS. Therefore, a response action is not required at this time.

Next Steps:
Continued response action with an emphasis on maintaining dissolved oxygen level above 1.0 mg/L. The increase in biological activity in the plume source area has decreased dissolved oxygen to concentrations generally less than 1.0 mg/L, which indicate anaerobic conditions. As the groundwater becomes anaerobic, the CI-Out bacteria will begin to die as the naturally occuring bacteria begin to dominate, resulting in an incomplete degredation pathway and the accumulation of PCE daughter products.

Cost to Design and Implement:
$102,758.52