Unconsolidated overburden and Passaic Formation siltstone, mudstone, and shale underlie the site. Bedding planes within the site strike N65°E and dip approximately 10°NW. Glacial outwash and alluvial sediments, areas of man-made fill, and weathered, clay material comprise the overburden. The overburden ranges from 6 to 16 feet and lies over bedrock.
Ground water occurs within a shallow perched zone and within the bedrock layer. The perched zone is within the overburden, flows in the westerly direction, and occurs at depths of 5 to 10 feet below grade. Ground water within the bedrock occurs at depths of 20 to 30 feet below grade and flows along fractures. While groundwater in the region generally flows in the westerly direction, bedrock ground water at the site flows in an easterly direction due to industrial supply wells on the site.
Targeted Environmental Media:
 Dense Non-aqueous Phase Liquids (DNAPLs) - Fractured Bedrock
Not identified in the reference.
Major Contaminants and Maximum Concentrations:
- Benzene (Not provided)
- Toluene (Not provided)
- Ethylbenzene (Not provided)
- Xylenes (Not provided)
- Tetrachloroethene (Not provided)
- Trichloroethene (Not provided)
- Arsenic (Not provided)
- Fluid Loggings
- Pumping Tests
- Pump and Treat
Comments:
The project site is located in an industrially zoned area in Middlesex County. It consists of an industrial property on which arsenic-based pesticides were formerly manufactured to the east (Site A), a large chemical manufacturing complex (Site B) and a closed industrial landfill to the south (Site D), and an operating ground water treatment plant to the west (Site D). The ground water treatment plant was installed to treat shallow ground water impacts resulting from historic contamination originating from Site A.
Recently, the ground water remedy selected for the site in the early 1980s was re-evaluated and optimized based on current flow system concepts. Beginning in 2005, the responsible party for Site A installed and currently operates a ground water remediation system, collecting up to 50,000 gallons of ground water from the perched zone per day from a network of shallow drains and sumps. The water is treated to remove arsenic and VOCs prior to discharging to the local publicly owned treatment works (POTW). Since 2002, the responsible party for Sites B and C has operated a ground water remediation system to address VOC impacts to bedrock ground water. Ground water is pumped from a series of 36 extraction wells located on both sites, treated for VOC removal, and discharged to the POTW. The 36 extraction wells have operated at a combined flow rate ranging between approximately 4.9 gallons per minute (gpm) (7,000 gallons per day [gpd]) and 12.5 gpm (18,000 gpd).
New Jersey class II-A Groundwater Quality Standards
Additional optimization tests are being performed. Based on on-site contaminant concentrations and receptor proximity, hydraulic control measures will likely be included as a component of the final remedy for the project site.
Additional pumping tests indicated that simply increasing the pumping rate at the existing production well would not suffice to protect receptors or adequately remove contaminant mass. The revised conceptual site model (CSM) included an additional pumping location. This site profile highlights the evolving nature of site investigation and remediation practice, and the importance of employing a representative CSM when designing a remedy for ground water in fractured bedrock. It also highlights the need for conducting periodic reviews of remedy performance in light of new understandings and developments in science and technology.
References:
Peterson, James L. Geology Matters: Updating a Bedrock Ground Water Remedy at a New Jersey Site in the Newark Basin. Presented at the 2007 U.S. EPANGWA Fractured Rock Conference: State of the Science and Measuring Success in Remediation. Portland, ME. September 24-26, 2007.
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