Surficial geology consists of a glacial and marine till. The till thickens from less than 25 ft. to the west (upgradient) to about 80 ft. in the vicinity of Quiggle Brook to the east. The hydraulic conductivity of of the till is estimated to be 1x10-5 cm/s; the ground-water velocity under non-pumping conditions is approximately 15 ft/yr. A schist/gneiss bedrock containing granitic intrusions underlies the till. The upper 10 ft of the bedrock is weathered and has an estimated hydraulic of 8x10-5 cm/s. Seepage velocity through the bedrock fractures is approximately 300 ft/day.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
From 1967 to 1984, Union Chemical used the 12 acre site to manufacture solvents and recover petrochemical-based so0lvents. Spills from an onsite boiler, disposal of wastewater into an adjacent stream and wetlands, and leakage from storage containers contributed to extensive contamination of the area's soil and ground water. Contaminants were found in both the till and the weathered bedrock.
As of 2004 the shallow bedrock plume was approximately 480 feet long and 360 feet wide at its widest point.
Major Contaminants and Maximum Concentrations:
- 1,1,1-Trichloroethane (73,000 µg/L)
- Trichloroethene (84,000 µg/L)
- 1,1-Dichloroethene (2,700 µg/L)
- 1,1-Dichloroethane (12,000 µg/L)
- 1,2-Dichloroethene (19,000 µg/L)
- Ethylbenzene (2,700 µg/L)
- Tetrachloroethene (150 µg/L)
- Vinyl chloride (8 µg/L)
- Pumping Tests
- Other (Bromide tracer)
- Chemical Oxidation (In Situ)
- Permanganate
- Hydrogen Peroxide
- Pump and Treat
- Soil Vapor Extraction
- In Unconsolidated Overburden
- Bioremediation (In Situ)
- Reductive Dechlorination (In Situ Bioremediation)
- Other (hot air injection)
Comments:
In 1996, an SVE system augmented with hot air injection was implemented to enhance contaminant volatilization in the soil. The system consisted of 91 hot air injection wells over an area of 1.5 acres. Monitoring confirmed that by late 1998, two years after SVE treatment had begun, the soil had met the cleanup goal of 0.1 mg/kg.
A ground water extraction system operated from 1996 through 1999. Following a leveling of contaminant removal in 1997, an ISCO system began operating in 1998. Treatment involved the injection of a solution containing potassium permanganate (2%) and sodium permanganate (20% - 40%). Injections were performed in both monitoring and extraction wells screened throughout the till and bedrock. Over three summers, approximately 36,000 pounds of potassium permanganate and 7,300 pounds of sodium permanganate were injected. An application rate of 10 times the minimum amount estimated to oxidize the contaminants was used at each injection point.
Initial post-application data indicated VOC reductions of 30-99% in individual wells. Average concentrations of VOCs in the weathered bedrock decreased from 55-725 ug/l to 6-420 ug/l. Ethene contaminants generally responded to the permanganate more readily than ethane compounds, although some rebounding of TCE and DCE concentrations has occurred.
In August 2001, with DCE as the remaining contaminant, the system was converted to an anaerobic environment in order to increase the rate of reductive dechlorination. Food-grade molasses and sodium lactate were injected as carbon sources. In August 2002, sodium lactate was applied again, this time in all areas with elevated DCE concentrations. While post-application monitoring of water quality parameters indicated reductive conditions remained throughout the fall and winter, the April 2003 data were mixed. No significant DCA decrease could be attributed to the sodium lactate application, but a gradual increase of chloroethane (a daughter product of DCA) was observed.
Cleanup goals have not been met. Active treatment has ceased, however, monitoring will continue through spring and fall of 2004.
In the fall of 2004, EPA and the state of Maine are considering a TI waiver.
Drinking water MCLs
Approximately 475 pounds of VPCs remain in the subsurface. More than 10,000 pounds have been removed using this multiple approach. Currently, the till's low permeability is recognized as the limiting factor in complete removal. Contaminant data indicate that the plume footprints in the till and the weathered bedrock have reached equalibrium and are not anticipated to migrate beyound the site boundries. The installation of additional bedrock wells is underway to confirm these conditions.
Total capitol costs for the pump and treat and SVE systems were $9,500,000. The average annual operation and maintenance costs were $600,000. The cost of the ISCO system was $150,000.
As of September 2006, Regulators were monitoring the results of another oxidation injection .
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