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Remedy for the Riggs Park Community
(Updated February 10, 2009)
History of Contamination in Riggs Park
- In October 1989, there was a reported release of an unknown amount of gasoline from an underground storage tank in a Chevron Service Station located at 5801 Riggs Road in Chillum, Maryland. The release was initially addressed by the Maryland Dept. of the Environment (MDE). MDE required Chevron to install a pump and treat system to remove the gasoline from the ground water. The system has been in operation since 1990.
- In April, 2001, the gasoline plume was reported to have migrated into the District of Columbia, underlying a residential area known as the Lamond-Riggs Park community. The community is just south of the boundary between the District and Maryland.
- In October 2001, then-Councilmember Adrian Fenty asked EPA to assume responsibility for the gasoline release investigation. Through a series of orders, EPA has required that Chevron investigate the extent of groundwater and vapor contamination, expand the operation of the existing pump and treat system, and install vapor mitigation systems in certain homes.
- EPA separately investigated Perchloroethylene (PCE), but concluded that levels were low, and/or not attributable to contaminated groundwater.
- In addition to the testing performed by Chevron pursuant to the EPA Orders, there have been additional studies, including additional vapor contamination testing by the District. Most recently, in January, 2008, SS Papadopoulos performed an exhaustive study of more than 100 homes, taking in-home air samples, outdoor ambient air samples, sub-slab vapor samples and sub-surface samples. These tests were completed in September, 2008.
- Based upon its review of the 2008 data and an administrative record, DDOE has developed this Remedy for the Riggs Park site.
Summary of the District’s 2008 Study
- Approximately 20% of Riggs Park homes were tested in 2008, and NO homes had gasoline constituents present at concentrations that exceed the 1 x 10-5 cancer risk level.
- By contrast, solvents, including Perchloroethylene (“PCE”), its degradation products, and other non-gasoline contaminants were present in 42 homes at concentrations exceeding the 1 x 10-5 cancer risk level, and in some instances, at concentrations exceeding the 1 x 10-4 level.
- The extent of PCE contamination is unknown.
- The number of additional homes impacted by PCE is unknown.
Remedy
- Install VMS in 45 homes which Papadopulos data show have unacceptable risk, and/or have gasoline constituents present that are attributable to groundwater contamination.
- Confirm during design that the contaminants at the 45 homes are attributable to groundwater
contamination.
- Impose deed restrictions and obtain covenants at 45 homes.
- Perform health survey to determine if additional homes require VMS because of the presence of children and other sensitive subpopulations.
- Provide new PCE data to EPA for review; determine whether any additional homes require VMS based on potential for PCE vapor intrusion.
For information on implementation of the remedy, please contact Victoria North, DDOE, at (202) 535-1909 or Victoria.North@dc.gov
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