Fractured crystalline gabbro-diorite
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
The contaminant source in soil was removed in 1999; however, the plume was approximately 180 ft. long, 200 ft. wide and 200 ft. thick.
Major Contaminants and Maximum Concentrations:
- Tetrachloroethene (7,200 µg/L)
- Coring
- Chemical Oxidation (In Situ)
Comments:
In initial pilot tests, it was concluded that recirculation of ground water amended with permanganate was necessary to improve oxident delivery to the PCE source zone. An estimated 900,000 gallons of treated water was amended with 385 gallons of 40% NaMnO4 during five months of recirculation in August 2002. Post-treatment monitoring, while the system was shutdown indicated PCE rebounded to 6,600 ug/L at a source well 8 months after shutdown.
This was a pilot test.
Options are being considered to enhance the connectivity of the bedrock fractures in the contaminant source zone.
This information was reported in the 2004 U.S.EPA/NGWA Fractured Rock Conference, September 13-15, 2004, Portland, ME
Complete oxidation of the PCE source was limited by delivery of insufficient oxidant mass to the source zone relative to the mass of the PCE source. Heterogeneities limited delivery.
|
