Mid-Atlantic Superfund

EPA Region 3 (Mid-Atlantic)

Delaware
Kent County
Dover

EPA ID# DED980693550

1st Congressional District

Last Update: January 2009

Other Names

None

Current Site Status

EPA has continued to work with the potentially responsible parties via a consent decree to remediate the site. On August 19, 2002, EPA conducted the final on-site inspection of the finished parking lot. This parking lot was built as part of the site cleanup, and the lot will function as a cap to contain the contaminated soils. The site and its perimeter were graded and seeded.

Early last year, First Energy (formerly General Public Utilities Corporation) completed a groundwater investigation to define the extent of the perchloroethylene contamination. EPA formally accepted the results of this study in December 2005 and is using it to plan a site-wide supplementary groundwater investigation, intended to fill any remaining data gaps. EPA completed groundwater sampling for the first phase of this investigation in April 2006 and just recently completed the second phase of groundwater sampling in January 2008. EPA also conducted an initial round of vapor intrusion testing at several locations in Dover in April 2008 and completed that effort in July 2008. EPA is currently planning to continue the groundwater investigation during the Summer of 2009 to complete the characterization of groundwater contamination beneath the City of Dover. A Five- Year Review is planned for the Site later this year.

Site Description

The one-acre Dover Gas Light Co. site originally operated as a coal gasification plant. From 1859 to 1948 it produced gas from coal. This gas was used for street lamps and other purposes. When the plant was closed in 1948, all of the structures except a brick garage were demolished. Much of the plant was removed, but sections of the tanks and other process equipment were buried on site. These underground structures contained coal oil and/or coal tar. In 1984, remains of the coal gasification plant were found.

For several years the site was used as an unpaved parking lot for a museum next door. That parking lot area is now paved. A cemetery and historic church are located on the same block. Approximately 10,000 people are within one mile of the site and an estimated 45,000 people are served by public and private wells within three miles of the site. Seven of Dover's 14 municipal supply wells are located within one mile of the site; however, the Dover municipal system draws water from a lower, uncontaminated aquifer. The municipal wells were sampled in 1988 and 1991 and did not show signs of contamination. These wells were sampled again during the supplementary groundwater investigation currently underway.

Site Responsibility

Cleanup of this site is the responsibility of federal and state governments, and parties potentially responsible for site contamination.

NPL Listing History

This site was proposed to the National Priorities List of the most serious uncontrolled or abandoned hazardous waste sites requiring long-term cleanup action on January 22, 1987. The site was formally added to the list on October 4, 1989, making it eligible for federal cleanup funds.

Threats and Contaminants

Specific contaminants detected in the groundwater and soil include volatile organic compounds (VOCs) such as benzene, toluene, ethylbenzene, and xylenes, and polynuclear aromatic hydrocarbons or creosote-type compounds from former site activities. Releases of perchloroethylene (a dry cleaning solvent) from a nearby dry cleaner have also contributed to the groundwater contamination at this site.

Contaminant descriptions and risk factors are available from the Agency for Toxic Substances and Disease Registry, an arm of the CDC.

Cleanup Progress

EPA's decisions on how to address site contamination are formally outlined in legal documents known as Records of Decision. The first Record of Decision (ROD) for this site was issued on August 16, 1994. In it, EPA called for the excavation of contaminated soils and off-site treatment. Also, EPA selected a combination of containment and natural attenuation for the groundwater.

In May 1995, EPA sent legal paperwork to Chesapeake Utilities Corporation and to General Public Utilities Corporation, ordering them to implement the ROD. Only Chesapeake Utilities Corporation complied with this May 1995 order.

In December 1997, EPA modified the soil cleanup requirements. Contaminated soil would be excavated from within the three underground brick structures used for holding gas. Remaining soil contamination would be addressed by using soil vapor extraction (SVE) technology and capping the one-acre lot with an asphalt parking lot.
In 1998, Chesapeake finished excavating soils from inside the gas holders. In 2000, the SVE system finished removing soil contamination from the remaining soil. This work included: non-aqueous phase liquid (NAPL) monitoring and recovery, soil vapor extraction and gas holder remediation and involved constructing a parking lot. On April 25, 2002, Chesapeake Utilities Corporation (CUC) began the parking lot construction. The parking lot construction, among other things, restricts exposure to soils and limits stormwater infiltration in soils. CUC completed soil cleanup work in September 2002.

In 2000, design for the groundwater containment system was stopped to further reconsider the releases of perchloroethylene from a nearby dry cleaner. First Energy (formerly General Public Utilities Corporation) completed a groundwater investigation to define the extent of the perchloroethylene contamination. EPA formally accepted the results of this study in December 2005.

EPA used the 2005 ground water investigation completed by First Energy to plan a site-wide supplementary groundwater investigation, intended to fill any remaining data gaps. EPA completed groundwater sampling for the first phase of this investigation in April 2006 and completed the Phase 2 of the groundwater investigation, including sampling sediments and groundwater in the vicinity of the St. Jones River, east of the former Dover Gas Light Company facility and installing several new monitoring wells in January 2008. EPA also conducted an initial round of vapor intrusion testing in July 2008 to evaluate the potential for vapors from VOCs in the contaminated groundwater to enter and/or accumulate in ground-surface structures above. EPA is currently planning to continue the groundwater investigation during the Summer of 2009 to complete the characterization of groundwater contamination beneath the City of Dover. A Five- Year Review is planned for the Site later this year.

Contacts

Site Contacts

Administrative Record Locations