The site was a former commercial laundry/dry cleaning business that operated from 1937 to 1997. Dry-cleaning initially used a non-chlorinated petroleum hydrocarbon-based solvent. In 1960 tetrachloroethene (PCE) replaced the previously used solvent.
The main compounds of concern in soil and groundwater at the site were PCE and other chlorinated volatile organic compounds (CVOCs). The closest surface water is the Contoocook River, which is located about 225 meters from the site. The general northwesterly groundwater flow shifts to a northerly flow off the site. It is possible that it follows a route aligning with the surface water flow of the Contoocook River. It is also worth noting that the stronger hydraulic correlations stop once the groundwater direction turns to the north.
Targeted Environmental Media:
 Fractured Bedrock
Not documented.
Major Contaminants and Maximum Concentrations:
- Tetrachloroethene (var)
- Nonhalogenated VOCs (var)
- Tracer (dye) Test
- Other (background fluorescence analysis (BFA))
Comments:
The fractured bedrock setting of the site made it challenging to evaluate preferential groundwater flow using conventional hydrogeologic investigation tools. A background fluorescence analysis (BFA) study was conducted to outline areas of concern quickly and to evaluate preferential groundwater flow and interconnectivity between the existing monitoring wells. A fluorescent dye-tracing (FDT) test identified hydraulic connections identified through the BFA, assessed groundwater seepage velocities, and helped to evaluate the most effective remediation scenario. In 2010, four different fluorescent dyes were used. Immediately after dye placement, a small artificial hydraulic gradient was created by adding about 25 to 100 liters of spring water into each well to ýpushý the dye into the aquifer. After the dyes were applied in the placement wells, the wells were closed and marked to prevent cross-contamination. Groundwater samples for FDT analysis were collected from 39 sampling locations, using standard operating procedures to identify dye breakthrough.
- Bioremediation (In Situ)
Comments:
Remediation was implemented using an injection of Anaerobic Biochem with a Zero-Valent (ABC+) in a two tiered approach. The first application of the amendment was implemented through a perforated pipe trenching network installed in the release area set on bedrock. The second application was conducted through injections in both the shallow overburden and deep bedrock aquifers.
Not documented.
Full-scale remediation is planned. The site investigation team identified that general northwesterly groundwater flow changes offsite to a northerly flow. It is possible that it follows a route parallel to the surface water flow of the Contoocook River. It is also worth noting that the stronger hydraulic correlations cease to exist once the groundwater direction turns to the north. Through the end of the observation period, none of the fluorescent dyes could be detected in the Contoocook River.
The data collected was crucial in designing the remedial program in accordance with the New Hampshire Department of Environmental Services Remedial Action Plan (RAP) requirements. The RAP proposed the injection of Anaerobic Biochem with a Zero-Valent (ABC+) in a two tiered approach. This remedial approach was one of the first of its kind approved in the State of New Hampshire.
Reference:
Gendron, K.J. "Background Fluorescence Analysis (BFA) and Fluorescent Dye-Tracing (FDT) used in Evaluating the Impacts of a Dry-Cleaning Facility in a Fractured Bedrock Setting". 8th International Conference Remediation of Chlorinated and Recalcitrant Compounds. May 21-24, 2012. Page A2.
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