To evaluate the impact of the oil spill, the trustees conducted multiple studies, which are outlined here. The detailed findings are available in the restoration plan and environmental assessment and appendices. For additional information, contact John Collins.

To expedite restoration of injured resources, the trustees and those responsible for the spilled oil (Potomac Electric Power Company (PEPCO) and ST Services) worked cooperatively to assess injuries and determine restoration needs. After conducting multiple reviews and analyses, the trustees determined that oil affected the following resources:

Marshes

Overall, 76 acres of marsh were lightly, moderately, or heavily oiled. Wetland experts quantified the scope and extent of oiling in the marshes along the Patuxent River and its tributaries by using field observations and aerial photography. Their estimates were correlated with subsequent measures of marsh vegetation health in oiled and unoiled areas.

Benthic Invertebrates

Studies found that 4,976 pounds of benthic invertebrates were lost. Using the Benthic Index of Biotic Integrity (B-IBI) developed for use in the Chesapeake Bay, samples were taken in the Patuxent River, Swanson Creek, and Hunting Creek (the latter as a reference) to determine changes in abundance, biomass, and species diversity.

Diamondback Terrapins

The spill resulted in 122 dead diamondback terrapins. There was a 10 percent reduction in hatchlings in 2000.

Finfish, Shellfish, and Crabs

An estimated 5,432 pounds of finfish, shellfish, and crabs were lost. For all, mortality was estimated using:

• Counts from field surveys and data collected on the number and species of larvae and eggs present at the time of the spill.
• Water column concentrations of petroleum hydrocarbons.
• Levels of hydrocarbons in tissues.
• Results from toxicity tests.

These data were compared to those in the literature.

Birds (Ospreys, Great Blue Herons, Bald Eagles, and Waterfowl such as Ruddy Ducks)

The number of lost birds was 696. Scientists visually monitored nests to document the number of oiled or dead adult, young, and eggs of ospreys, great blue herons, and bald eagles. For ospreys, data gathered after the spill were compared to both historical data from the area and data from nests upstream of the spill area. For great blue herons, these data were compared to a Black Swamp Creek control site and data in the literature. Bald eagle chicks were monitored until they fledged.

Many other species, but especially ruddy ducks, were oiled or killed by the spill. These numbers, as well as qualitative surveys of birds conducted during the spill, were used to estimate total waterfowl species mortality.

Furbearers

An estimated 376 furbearers, primarily muskrats, were lost. The loss of furbearing animals was estimated using oiled wildlife mortality counts maintained by the U.S. Fish and Wildlife Service, data collected by local trappers, historical surveys from other areas, and the literature.

Lost Human Use

The impacts to recreational fishing, boating, and shoreline use (such as swimming, picnicking, and wildlife viewing) were assessed, and it was found that 10 acres of beaches were lightly, moderately, or heavily oiled, and 125,000 river trips were affected. Private losses, such as lost income or damaged fishing gear, were handled through a private claims process.