HAMILTON TOWNSHIP, NJ
On this page:
- What Has Been Done to Clean Up the Site?
- What Is the Current Site Status?
- Sampling and Monitoring
On related pages:
The D'Imperio Property site is located in a triangle formed by the intersections of U.S. Route 322 (Black Horse Pike), U.S. Route 40 and Cologne Road in Hamilton Township, New Jersey. The D'Imperio Property site is a 15-acre parcel of undeveloped real estate, of which an acre was used as an unauthorized dump in the mid-1970's. The disposal area consisted mainly of partially buried and ruptured metal drums. Many of the drums contained metals and various volatile organic compounds (VOCs), including solvents. The groundwater is contaminated, and the contaminant plume has been detected in two aquifers. The site was originally located in a semi-rural area that has subsequently undergone significant development. Approximately 6,000 people within 3 miles of the site use groundwater for drinking. Twenty private wells are located within 1 mile, with the closest well 300 feet upgradient of the site. The site is within the New Jersey Pineland Reserve. The Babcock Swamp wetlands, which are drained by Babcock Creek, are approximately 2000 feet to the southwest. This site is being addressed through federal and responsible party actions.
By securing the site with a fence, removing contaminated soil and drums, and putting in groundwater treatment and soil vapor extraction systems, EPA believes the potential for exposure to contaminated materials and groundwater at the site has been significantly reduced.
What Has Been Done to Clean Up the Site?
In 1987, EPA removed 82 buried drums and 3,900 cubic yards (6,240 tons) of contaminated soil and disposed of it at an approved off-site facility. In August 1993, EPA issued a Unilateral Administrative Order (UAO) to 14 potentially responsible parties (PRPs) requiring them to perform a groundwater investigation to define the extent of the contaminated groundwater, and construct and operate a groundwater pump and treatment system. The PRPs completed the groundwater investigation in November 1994 and the construction of the groundwater pump and treatment system in August 1996. The site’s groundwater treatment system has been fully operational since August 1997. The groundwater extraction and reinjection system was expanded in April 1999 to include the contaminated Lower Cohansey Sand Aquifer.
After conducting a soil study of the former disposal area and determining that contaminated subsurface soils remained, EPA issued a modification to the 1993 UAO that required the PRPs to perform additional soil sampling of the former disposal area. The results of the soil study are summarized in the October 2002 soils evaluation report. The findings were used to issue the 2003 ROD Amendment which changed the final component of the remedy selected in the ROD from a cap over the former disposal area to soil vapor extraction, or SVE. EPA issued a UAO for the SVE remedial design/remedial action, or RD/RA in November 2003. The design build and construction activities were completed in July 2004 and operations began in August 2004.
With the SVE system operational, the site remedy is construction complete. EPA issued a preliminary close–out report, or PCOR in September 2004 and approved the PRPs interim remedial action report in December 2004. Currently, 13 SVE wells operate to reduce contaminated vapors within the subsurface soils, with monthly performance maintenance and biannual air monitoring of the system.
As part of our on-going effort to ensure the effectiveness of the groundwater treatment system, EPA required the PRPs to initiate a supplemental groundwater investigation (SGI) in 2003 for the purpose of evaluating the current conditions and quality of the groundwater, and to update the groundwater flow model. The investigation found that conditions in the contaminated portion of the Lower Cohansey Aquifer had changed, making it necessary to perform additional remedial activities. An SGI report and Lower Cohansey groundwater system enhancement, or LCGWES, scope of work was submitted by the PRPs in June 2004. Additional investigation activities were conducted between June 2004 and May 2005. These activities resulted in the Lower Cohansey groundwater delineation report and revised LCGWES approved by EPA in July 2005. The PRPs conducted the LCGWES construction activities from July to December 2005 and the new system was integrated into the ongoing groundwater treatment system in February 2006. The March 2007 operation and maintenance plan addendum and May 2007 revised long-term groundwater monitoring plan were approved by EPA in October 2007, and the April 2006 LCGWSE certification report for construction activities was approved by EPA in January 2008.
EPA issued an Explanation of Significant Differences, or ESD on March 2010 to incorporate the CEA requirement into the groundwater remedy selected in the 1985 ROD.
To address a small, detached groundwater plume in the Lower Cohansey Aquifer, or LCDP, the PRPs began activities in April 2011 to expand the extraction system. After several years of conducting investigation activities that included well installation and sampling, the PRPs submitted the LCDP delineation report in August 2014. Subsequently, the PRPs submitted an updated site groundwater flow model and LCDP groundwater optimization strategy in October 2014, and the LCDP Optimization Implementation Work Plan in November 2014 for containing and treating this detached plume. These documents were approved by the EPA in December 2014. Design optimization activities were performed in February and March 2015 and the optimization construction activities to connect three new extraction wells to the existing treatment system were conducted between June and November 2015. The LCDP extraction system has been operational since December 2015.
PRPs submitted a draft revised long-term groundwater monitoring plan (LTGWMP) and quality assurance project plan (QAPP) in June 2018 pursuant to the optimization of the groundwater monitoring program to address the current plume and remediation system operational conditions.EPA approved of the LTGWMP-Revision 3a and revised QAPP on March 13, 2020. which reduced the site groundwater monitoring from quarterly to semi-annual.
Five Year Reviews
An initial five-year review, or FYR report was issued by EPA in July 2009. These reviews ensure that the remedies put in place protect public health and the environment, and function as intended by site decision documents. This initial FYR concluded that response actions at the site are in accordance with the remedy selected by EPA and that the remedy continues to be protective of human health and the environment.
A second FYR was issued on August 1, 2014. The findings from this second review concluded that the soil vapor extraction (SVE) continues to reduce the source of groundwater contamination while the pump and treat system effectively contains the contaminated groundwater plumes. The established performance criteria are being met and performance monitoring will continue to evaluate the soil and groundwater cleanup processes.
A third FYR was issued on August 30, 2019. The results of the review shows that the SVE system continues to reduce the source of the groundwater contamination while the pump, treatment and reinjection system effectively contains the contaminated groundwater plumes. However, the mass removed per month by the SVE system is diminishing which may require optimization to enhance the final stage of the remediation process. The groundwater pump treatment and reinection system continues to contain the contaminated groundwater plumes. Both systems are meeting the established performance criteria and performance monitoring will continue to evaluate the soil and groundwater cleanups.
What Is the Current Site Status?
The site is being addressed in two stages: an immediate action and a long-term remedial phase focused on cleanup of the entire site.
Immediate Action: In 1982, EPA put in a fence to prevent people from entering the site and coming into contact with hazardous substances.
Long-term Cleanup: EPA selected the remedy in the site’s 1985 Record of Decision, or ROD. It included: (1) digging up and transporting about 3,900 cubic yards of contaminated waste, soil and drums to an approved off-site facility; (2) placing a cover or cap over the former disposal area; and (3) pumping and treating the groundwater to remove the contaminants and then discharging the clean water back into the aquifers. EPA modified the remedy in the 2003 ROD Amendment to include soil vapor extraction (SVE) for remaining contaminated subsurface soils instead of placing a cap over the former disposal area. EPA again modified the ROD in the 2010 Explanation of Significant Differences , or ESD to include the State’s Classification Exception Area (CEA) requirement as part of the groundwater remedy.
Monthly sampling and operation and maintenance activities of the soil and groundwater treatment systems will continue while site soil vapor and groundwater quality will be monitored semi-annually. The PRPs are expected to submit a final revised CEA for the State’s approval.
Sampling and Monitoring
During the operation and maintenance phase, site soil and groundwater monitoring wells are sampled semi-annually while the treatment systems are monitored monthly, This information is documented in monthly and semi-annually reports.