Remediation Status: Site closed

Why the technology was selected:
In-situ bioremediation was selected because aquifer conditions are anaerobic (dissolved oxygen concentrations in groundwater ranged from 0.3 to 0.7 mg/L) and reductive dechlorination was occurring (TCE and cis 1,2-DCE were present in groundwater).

Date implemented:
Potassium Lactate Injection: August 2004

Final remediation design:
In-Situ Bioremediation: Two one-inch-diameter Schedule 40 PVC injection wells (screened 2-12 ft bgs) were installed using a direct push rig. A total of 500 lbs. of 60% potassium lactate, diluted with approximately 2000 gallons of water, were injected in the wells at 15 PSI, a rate of approximately 0.75 gpm. The injection wells were then flushed with 400 gallons of water, with 6.5 grams of sodium thiosulfate added to flush any residual potassium lactate from the injection wells that could result in biofouling.

Results to date:
The SVE system operated from September 6, 2000 until July 25, 2001. An estimated 3 lbs. of VOCs were recoved. Confirmatory soil sampling did not detect any contaminants in soils in concentrations exceeding cleanup target levels for leachability. Continued groundwater monitoring showed a rebound in contaminant concentrations (PCE and TCE were detected in concentrations as high as 5.8, and 18.6 µg/L, respectively, in two monitor wells located in the contaminant source area. At that time, the decision was made to inject potassium lactate to "polish" contaminated groundwater at the site. The potassium lactate injection resulted in a reduction of contaminant concentrations in groundwater below cleanup target levels.

Next Steps:
The site has met the No Further Action criteria, and a Site Rehabilitation Completion Order will be issued.

Cost to Design and Implement:
$102,400 for all technologies

Why the technology was selected:
SVE was selected because it is an effective technology for removing VOCs from unsaturated permeable sediments (fine to medium-grained sand at this site).

Date implemented:
SVE: September 2000

Final remediation design:
SVE System: A 5-foot lateral vapor extraction well was installed at a depth of 3 ft bgs, just outside the wall opposite the location of the drycleaning machine. The lateral was constructed of 4-inch-diameter Schedule 40 PVC with 0.02-inch slot. The system was powered by a 3-HP rotary lobe blower. A 55-gallon moisture separtor was utilized, and vapors were treated with two 175-lb. G.A.C. units.

Results to date:
The SVE system operated from September 6, 2000 until July 25, 2001. An estimated 3 lbs. of VOCs were recoved. Confirmatory soil sampling did not detect any contaminants in soils in concentrations exceeding cleanup target levels for leachability. Continued groundwater monitoring showed a rebound in contaminant concentrations (PCE and TCE were detected in concentrations as high as 5.8, and 18.6 µg/L, respectively, in two monitor wells located in the contaminant source area. At that time, the decision was made to inject potassium lactate to "polish" contaminated groundwater at the site. The potassium lactate injection resulted in a reduction of contaminant concentrations in groundwater below cleanup target levels.

Next Steps:
The site has met the No Further Action criteria, and a Site Rehabilitation Completion Order will be issued.

Cost to Design and Implement:
$102,400 for all technologies

Date implemented:
SVE: September 2000

Final remediation design:
SVE System: A 5-foot lateral vapor extraction well was installed at a depth of 3 ft bgs, just outside the wall opposite the location of the drycleaning machine. The lateral was constructed of 4-inch-diameter Schedule 40 PVC with 0.02-inch slot. The system was powered by a 3-HP rotary lobe blower. A 55-gallon moisture separtor was utilized, and vapors were treated with two 175-lb. G.A.C. units.

Next Steps:
The site has met the No Further Action criteria, and a Site Rehabilitation Completion Order will be issued.

Cost to Design and Implement:
$102,400 for all technologies