Remediation Status: Site closed

Why the technology was selected:
Since PCE degradation products were present in groundwater, HRC was proposed to enhance biodegradation by fueling reductive dechlorination in an offsite source area (50 ft x 70 ft) Exacation was recommended to remove contaminated soils - onsite and offsite.

Date implemented:
Excavation: 1999 HRC Injection: June 2001

Final remediation design:
Approximately 146 cubic yards of contaminated soil were excavated in two areas: beneath the floor slab of the former drycleaning facility (2-3 ft in depth) and at an offsite location in the vicinity of a monitor well. A total of 25 injection points (open-hole) were installed on a 10-ft spacing at an offsite location. A straddle packer was used to isolate the injection zone (limestone). The limestone was fractured by injecting HRC at high pressure in a zone 15-25 ft bgs. Slightly less pressure (40-60 psi) was used to inject HRC at shallower depths (5-15 ft bgs). On average, 136 pounds of HRC was injected per borehole. A total of 3,400 pounds of HRC was injected at the site or an average of 6.7 lb/ft/borehole.

Results to date:
Between June 2001 (injection event) and April 2002 monitoring indicated that groundwater wells located proximate to the injection area had not been significantly influenced by the HRC application. Nearly two years after treatment, PCE concentrations in one monitoring well located in the injeciton zone have increased from 15,000 µg/l to 23,500 µg/l.

Next Steps:
No groundwater monitoring required anymore. Excarvation performed and site eventually closed. A certificate of completion was issued on November 12,2007.