Remediation Status: In active remediation

Why the technology was selected:
Bioremediation using Cl Solution's Cl-Out was chosen for the pilot study as a method to enhance degradation of contaminants in groundwater. Reductive dechlorination is occurring in groundwater.

Date implemented:
Excavation & infiltration:- December 17-19, 2001 Cl-Out injection - January 23, 2002 ABC injection: February 15, 2006 ABC injection: September 14, 2008

Final remediation design:
Following a bench-scale study of Cl-out, a pilot test was designed to be implemented concurrently with the soil excavation. A portion of the building floor slab was removed and approximately 5.4 cubic yards of contaminated soil was hand-excavated to a depth of 6 ft. The pilot test consisted of two injection events, conducted a month apart. The Cl-Out treatment was infiltrated into the source removal excavation in December 2001 and then the CL-Out solution was introduced into the subsurface through injection wells installed inside the facility in January 2002. Number of injection events: 2 3 Injection wells: 2 - 1" diameter PVC wells screened 5-10 ft bgs & 1 one and one-half inch diameter PVC well screened 5-10 ft bgs. Quantity per event: 55 gallons of solution (50 lbs. of dextrose & ~ 109 colony forming units (CFU)/milliliter of bacteria (Pseudomonous sp.) Quantity per well: ~ 20 gallons Injected with variable speed peristaltic pump ~ 1 gallon/minute. Subsequently, there have been two additional bioremedial injection events using ABC (Anaerobic BioChem). ABC is a mixture of potassium lactate, soybean oil and a phophate buffer. The same three injection wells were utilized as for the CL-Out injections. Each injection event utilized 420 gallons of a 15% by weight ABC solution (140 gallons per well).

Results to date:
Within the first two years after the CL-Out injections, contaminant concentrations in groundwater samples collected from the source area monitor well showed a drop in PCE concentration to 96 ug/l (three orders of magnitude less than the pre-injection concentration). The TCE concentration also dropped (to 27.9 ug/l). There were corresponding increases in the concentrations of Cis 1,2-DCE and vinyl chloride. However, PCE and TCE concentrations rebounded to 1000s of ug/l in 2005 and 2006, indicating that parent contaminant mass still remained in the source area. Following the first ABC injection event, PCE and TCE concentrations increased in the source area monitor well but then decreased after the second ABC injection event. Concentrations of Cis 1,2-DCE showed an initial increase (to 35,600 ug/l) and then declined. Vinyl chloride concentrations have esentially remained flat (3,890 to 4,000 ug/l). No PCE and very little TCE had been detected in groundwater samples collected from downgradient monitor wells during the site assessment. Cis 1,2-DCE concentrations as high as 3,080 ug/l declined to 67 ug/l after the CL-Out injections and then rebounded. After the ABC injections, Cis 1,2-DCE concentrations have dropped well below the MCL. Vinyl chloride concentrations in downgradient montior wells dropped after the Cl-Out injections and then rebounded. After the ABC injections, vinyl chloride concentrations in downgradient monitor wells have dropped and range from non-detect to 18 ug/l.

Next Steps:
When local permits are approved a soil vapor extraction system will be installed to recover VOC contamination in the unsaturated zone not removed by the excavation.

Cost to Design and Implement:
Feasibility study: $4,658 Cl-Out injection: $7,100 Well installation, sampling & reporting: $20,708

Why the technology was selected:
Excavation was chosen as a more practical removal technology for soil contamination than SVE, because the drycleaning machine had been removed and the source area was accessible. Also, there is little room for a remedial system at the site.

Date implemented:
Excavation & infiltration:- December 17-19, 2001 Cl-Out injection - January 23, 2002

Final remediation design:
A portion of the building floor slab was removed and approximately 5.4 cubic yards of contaminated soil was hand-excavated to a depth of 6 ft.

Next Steps:
When local permits are approved a soil vapor extraction system will be installed to recover VOC contamination in the unsaturated zone not removed by the excavation.

Cost to Design and Implement:
Soil excavation & removal: $18,000