Remediation Status: In active remediation

Why the technology was selected:
Chemical oxidation using Cool-Ox (calcium oxide +2% hydrogen peroxide) was chosen to remediate the unsaturated zone at the site because most of the contaminated soil was located beneath a building that houses an active drycleaning operation and a shallow water table (less than 3 ft BLS, seasonally) makes operation of a soil vapor extraction system problematic.

Date implemented:
Cool-Ox was injected from November 13-16, 2007.

Final remediation design:
The Cool-Ox was delivered via 132 injection points installed on a 3 foot grid. A total of 34 injection points (3/4-inch boreholes) were installed beneath the facility floor slab in two general areas: 18 points located adjacent to the drycleaning machines and 16 points located inside the southeast corner of the building. The remaining 98 points were installed in the area outside of the southwestern corner of the building. This included the delivery door of the facility and the area near the stormwater drain. A total of 4,224 gallons of reagent was utilized or approximately 32 gallons of reagent per injection point. The Cool-Ox was injected using Hydro Dart at pressures of up to 500 p.s.i. The injection rate ranged from 2 to 2.5 gpm.

Results to date:
Conducted membrane interface probe logging (7 boreholes to 41 ft BLS) at the site June 5-7, 2009 and collected soil samples beneath buiding floor slab. All soil samples had detectable concentrations of PCE, ranging from 140 - 5,200 ug/kg, indicating that the Cool-Ox injection was not effective in remediating contaminated soil beneath the facility floor slab. Based on MIP and groundwater monitoring results, eight addtional monitor wells were installed at the site, including two wells installed beneath the drycleaning facility floor slab (screened across the water table). Highest contaminant concentrations in groundwater continue to be in the area just outside the service door of the facility adjacent to the sumps. Additional confirmatory soil sampling conducted in May 2010, found PCE concentrations ranging from 100 to 8,600 ug/kg in samples collected beneath the facility floor slab.

Next Steps:
Evaluating remedial technologies for the unsaturated zone. Large diameter vapor extraction wells are a possibility. Groundwater remedy will likely be bistimulation.

Cost to Design and Implement:
$131,200