Remediation Status: In groundwater monitoring

Why the technology was selected:
In-situ bioremediation via ethyl lactate injection/groundwater withdrawal and re-injection was chosen, because anaerobic conditions existed in the aquifer and reductive dechlorination was occurring. Ethyl lactate was chosen to stimulate biodegradation, because it is a relatively cheap carbon source. Groundwater withdrawal/injection was chosen to facilitate distibution of the ethyl lactate within the relatively heterogeneous aquifer.

Date implemented:
March 12, 2003

Final remediation design:
Groundwater remedial system: Twenty-two (22) injection wells constructed of 4-inch diameter, schedule-40 PVC were installed outside the south and west walls of the facility (hydraullically upgradient). Fifteen (15)shallow injection wells were screened 10-20 ft bgs with 0.10-inch slot. Seven deep injection wells were screened 30-40 ft bgs with 0.01-inch slot screen. Two recovery wells were installed outside the north (downgradient) side fo the facility. They were constructed of 5-inch diameter, Schedule-40 PVC with 0.020-inch slot screen. One well was completed in the shallow portion of the aquifer (5-20 ft bgs) and one well was completed in the deeper portion of the aquifer (25-40 ft bgs). A 1/3-horsepower Grunfos 10E-5 submersible pump was installed in the shallow recovery well and a 1/2-horsepower Grunfos 16-E submersible pump was installed in the deeper recovery well. The design recovery well pumping rates were 8 and 7 gpm for the shallow and deep wells, respectively. Recovered groundwater is treated in two 1000-lb liquid carbon vessels and then routed to a 300-gallon poly transfer tank where it is aerated to treat for vinyl chloride and then re-injected (into site injection wells) with a 1.5-horsepower Gould pump.

Results to date:
The SVE system operated from March 12, 2003 until September 6, 2005. The system operated at an average of 120 scfm at 13 inches of water column. The calculated radius of influence for each well was over 20 ft. Approximately 22.7 pounds of VOCs (99% PCE) were removed during the system operation. A total of thirteen (13) ethyl lactate injection events between March 2003 and March 2007. A total of 110 gallons of ethyl lactate was injected during each event (55 gallons in the shallow injection well and 55 gallons in the deep injection well) in a 1-2% solution. Ethanol was detected in recovery wells within one week of the initial injection event. Within three weeks of the first injection event, ethanol was not being detected in recovery wells. There was a rapid decrease in PCE concentrations in system influent in the first quarter of system operation coupled with an increase of cis 1,2-DCE in groundwater influent concentrations. Cis 1,2-DCE concentrations in groundwater influent began decreasing late in the first quarter of system operation, and vinyl chloride concentrations increased substantially. Vinyl chloride concentrations began to decrease in the fourth quarter of system operation. The groundwater extraction system was turned off on October 14, 2005. During the 2 ½ years of operation 9,621,700 gallons of groundwater were recovered for an average overall system flow rate of 9.8 gpm. Approximately 31 lbs. of VOCs were recovered during the system operation; the estimated total mass within the groundwater during the remedial action plan was 19.8lbs. System Influent Concentrations (in µg/l): 3/13/03--1,080 PCE, 991 TCE, 318 cis DCE, 8 trans DCE, 22 vinyl chloride. No PCE was detected in groundwater samples collected during the March 18, 2008 sampling event. The highest TCE concentration found was 3 ug/l. No contaminants were found in the contaminant source area in concentrations exceeding an MCL. The highest contaminant concentrations in groundwater were detected in monitor wells located from 120 to over 200 feet hydraulically down gradient of the former facility: 1,000 ug/l Cis 1,2-DCE and 65 ug/l vinyl chloride. The highest contaminant concentration that exceeded an MCL that was detected in a groundwater sample collected from an offsite monitor well was 2 ug/l vinyl chloride.

Next Steps:
Continue natural attenuation monitoring.

Cost to Design and Implement:
all technologies: Design: $32,300 Construction: $107,500

Why the technology was selected:
Natural attenation was chosen as the remedy for the distal portion of the contaminant plume. Since reductive dechlorination is occurring, treatment of high contaminant concentrations in the source area coupled with natural attenuation of the low contaminant concentrations in the distal portion of the plume should remediate the plume.

Next Steps:
Continue natural attenuation monitoring.

Cost to Design and Implement:
all technologies: Design: $32,300 Construction: $107,500

Date implemented:
March 12, 2003

Final remediation design:
SVE - Three 20-ft horizontal SVE wells constructed of 2-inch diameter, schedule-40 PVC were installed (one on each of three sides of the former facility) in a 2-ft-deep trench. The system is powered by a 2-horsepower Rotron EN505 230 blower. Off gas is treated via two 170-lb GAC units. The design flow rate is 90 scfm at 20 inches of water column vacuum. The design radius of influence for each SVE well is 20 ft.

Results to date:
The SVE system operated from March 12, 2003 until September 6, 2005. The system operated at an average of 120 scfm at 13 inches of water column. The calculated radius of influence for each well was over 20 ft. Approximately 22.7 pounds of VOCs (99% PCE) were removed during the system operation.

Next Steps:
Continue natural attenuation monitoring.

Cost to Design and Implement:
all technologies: Design: $32,300 Construction: $107,500

Why the technology was selected:
In-situ bioremediation via ethyl lactate injection/groundwater withdrawal and re-injection was chosen, because anaerobic conditions existed in the aquifer and reductive dechlorination was occurring. Ethyl lactate was chosen to stimulate biodegradation, because it is a relatively cheap carbon source. Groundwater withdrawal/injection was chosen to facilitate distibution of the ethyl lactate within the relatively heterogeneous aquifer.

Date implemented:
March 12, 2003

Final remediation design:
Groundwater remedial system: Twenty-two (22) injection wells constructed of 4-inch diameter, schedule-40 PVC were installed outside the south and west walls of the facility (hydraullically upgradient). Fifteen (15)shallow injection wells were screened 10-20 ft bgs with 0.10-inch slot. Seven deep injection wells were screened 30-40 ft bgs with 0.01-inch slot screen. Two recovery wells were installed outside the north (downgradient) side fo the facility. They were constructed of 5-inch diameter, Schedule-40 PVC with 0.020-inch slot screen. One well was completed in the shallow portion of the aquifer (5-20 ft bgs) and one well was completed in the deeper portion of the aquifer (25-40 ft bgs). A 1/3-horsepower Grunfos 10E-5 submersible pump was installed in the shallow recovery well and a 1/2-horsepower Grunfos 16-E submersible pump was installed in the deeper recovery well. The design recovery well pumping rates were 8 and 7 gpm for the shallow and deep wells, respectively. Recovered groundwater is treated in two 1000-lb liquid carbon vessels and then routed to a 300-gallon poly transfer tank where it is aerated to treat for vinyl chloride and then re-injected (into site injection wells) with a 1.5-horsepower Gould pump.

Results to date:
A total of thirteen (13) ethyl lactate injection events between March 2003 and March 2007. A total of 110 gallons of ethyl lactate was injected during each event (55 gallons in the shallow injection well and 55 gallons in the deep injection well) in a 1-2% solution. Ethanol was detected in recovery wells within one week of the initial injection event. Within three weeks of the first injection event, ethanol was not being detected in recovery wells. There was a rapid decrease in PCE concentrations in system influent in the first quarter of system operation coupled with an increase of cis 1,2-DCE in groundwater influent concentrations. Cis 1,2-DCE concentrations in groundwater influent began decreasing late in the first quarter of system operation, and vinyl chloride concentrations increased substantially. Vinyl chloride concentrations began to decrease in the fourth quarter of system operation. The groundwater extraction system was turned off on October 14, 2005. During the 2 ½ years of operation 9,621,700 gallons of groundwater were recovered for an average overall system flow rate of 9.8 gpm. Approximately 31 lbs. of VOCs were recovered during the system operation; the estimated total mass within the groundwater during the remedial action plan was 19.8lbs. System Influent Concentrations (in µg/l): 3/13/03--1,080 PCE, 991 TCE, 318 cis DCE, 8 trans DCE, 22 vinyl chloride. No PCE was detected in groundwater samples collected during the March 18, 2008 sampling event. The highest TCE concentration found was 3 ug/l. No contaminants were found in the contaminant source area in concentrations exceeding an MCL. The highest contaminant concentrations in groundwater were detected in monitor wells located from 120 to over 200 feet hydraulically down gradient of the former facility: 1,000 ug/l Cis 1,2-DCE and 65 ug/l vinyl chloride. The highest contaminant concentration that exceeded an MCL that was detected in a groundwater sample collected from an offsite monitor well was 2 ug/l vinyl chloride.

Next Steps:
Continue natural attenuation monitoring.

Cost to Design and Implement:
all technologies: Design: $32,300 Construction: $107,500

Why the technology was selected:
SVE is an effective technology for removal of VOCs from permeable unsaturated sediments.

Date implemented:
March 12, 2003

Final remediation design:
SVE - Three 20-ft horizontal SVE wells constructed of 2-inch diameter, schedule-40 PVC were installed (one on each of three sides of the former facility) in a 2-ft-deep trench. The system is powered by a 2-horsepower Rotron EN505 230 blower. Off gas is treated via two 170-lb GAC units. The design flow rate is 90 scfm at 20 inches of water column vacuum. The design radius of influence for each SVE well is 20 ft.

Results to date:
The SVE system operated from March 12, 2003 until September 6, 2005. The system operated at an average of 120 scfm at 13 inches of water column. The calculated radius of influence for each well was over 20 ft. Approximately 22.7 pounds of VOCs (99% PCE) were removed during the system operation.

Next Steps:
Continue natural attenuation monitoring.

Cost to Design and Implement:
all technologies: Design: $32,300 Construction: $107,500