Pepco's Response to the Mineral Oil Spill at Potomac River Power Station Investigation and Cleanup Complete, Monitoring and Assessments Continue

Pepco has been working diligently to clean up a spill of nontoxic mineral oil on January 23, 2011, at the Pepco substation on the west side of the Potomac River Power Station. The mineral oil leaked from a high-voltage transformer at our substation. The leak occurred in the early hours when a pipe separated from the transformer. The leak was quickly stopped; the majority of the mineral oil remained in the emergency containment reservoir or in the transformer itself, but an estimated 4,500 gallons escaped.

Some of that mineral oil reached the Potomac River to the east of the Pepco substation. As soon as Pepco discovered that the mineral oil had reached the river, we deployed absorbent booms to contain it. We then engaged trained spill-response contractors for cleanup and recovery on both land and water.

PHASE I: Containment & Recovery

In the days immediately after the leak, Pepco's contractors and employees worked around the clock to recover and properly dispose of all the collectible deposits of mineral oil from land and water.

PHASE II: Complete Cleanup

The next phase of the cleanup involved clearing caches of refuse that had collected along the shoreline; some of that material had contact with the leaked mineral oil. In many cases, dead trees and branches obscured the trash. Our contractors removed these slightly oiled materials for proper disposal. No live trees or shrubs were cut during the cleanup. Following advice from environmental, structural and mechanical engineering specialists, Pepco installed new equipment and improved maintenance and monitoring procedures — all designed to reduce the likelihood of a future spill. We also are following the recommendations in our comprehensive review of equipment and procedures at all Pepco substations to ensure they meet the same high standards

We continue to cooperate with local, state and federal officials, including representatives of the City of Alexandria Fire Department and Office of Environmental Quality; the District of Columbia Department of the Environment (DDOE); the Virginia Department of Environmental Quality (VADEQ); the EPA; the U.S. Coast Guard; the U.S. Fish & Wildlife Service; and the National Park Service. During the active cleanup and recovery phase, we met daily with their representatives.

PHASE III: Shoreline Monitoring and Assessment

Pepco has done voluntary monitoring and continues to meet DDOE and VADEQ monitoring requirements.

Pepco collected and analyzed representative samples of the mineral oil from the affected transformer and from the spill area. Analyses confirmed that the spilled material consisted entirely of mineral oil. The manufacturer of the mineral oil has identified the product as practically nontoxic. Pepco retained certified bird and wildfowl protection contractors to monitor the avian population on the river to make sure that the bird population had not been adversely affected by the escaped mineral oil.
Pepco prepared a Shoreline Assessment Plan to collect sediment and water samples along the shore of the Potomac River in the vicinity of the spill. This plan is designed to tell us if there is any residual oil in the river that needs further cleanup. Pepco also has submitted Ecological Risk Assessment (ERA) and Natural Resource Damage Assessment (NRDA) Work Plans to DDOE to determine potential impacts of any residual oil on the river ecology.
Soon after DDOE’s approval of the Shoreline Assessment Plan in November 2011, Pepco’s environmental contractors collected samples of river sediment and water at several locations up and down the Potomac River shoreline that were impacted by the spill. The sampling results indicated the presence of petroleum hydrocarbons, metals, and low concentrations of PCBs in the samples, although no strong matches to the mineral oil were identified. One year later, there is only limited evidence of oil impact to the River.
The ERA was conducted using chemical data from the sediment and water samples and biological data (benthic macro invertebrate samples) collected from the shoreline. ERA suggested a limited evidence of benthic ecology impacts with unknown attribution, probably related to historical spills and regional contributions from other sources,
The NRDA was conducted using data from the wildlife surveys, data on lost use of Mount Vernon trail provided by NPS, a conservative fate and transport computer model, and the ERA findings. The NRDA identified only limited natural resource injuries. Pepco is working with DDOE and the Natural Resource Trustees to identify appropriate mitigation measures.
Pepco’s environmental contractor is completing the draft reports of assessment results for submitting to DDOE.
Pepco staff continues to monitor the cleanup site.

The reports of assessment results will be made available to the public in the near future.

Questions?

If you have a specific question or concern that has not been addressed here, please call the Pepco Potomac River Cleanup Hotline: 202-872-2337.

Our goals are to thoroughly and completely clean up the spill and return the affected area at least to its pre-spill condition. Thank you for your patience while the cleanup is completed.