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Mitigating Impacts of Conowingo Dam on Susquehanna River, Chesapeake Bay

Conowingo Dam on Maryland's Susquehanna River.

The Conowingo Dam stores enormous amounts of sediment, phosphorus and other pollutants.

Photo courtesy of Matt Tillet

Case Overview

A coalition of conservation groups petitioned to be included in the Federal Energy Regulatory Commission (FERC) relicensing proceedings for the Conowingo Dam. The groups, Stewards of the Lower Susquehanna, their representative the Lower Susquehanna Riverkeeper, and Waterkeepers Chesapeake, plan to push the commission to require the dam’s owner, Exelon Generation, to take action to address and prevent harm to water quality in the Susquehanna River and Chesapeake Bay.

The Conowingo Dam stores enormous amounts of sediment, phosphorus, and other pollutants. When too much sediment reaches the Chesapeake Bay it clouds the bay’s waters, harming the underwater vegetation there and the animals that rely on it. While the dam has been trapping sediment since it began operation in 1928, scientists estimate that its retention capacity is rapidly diminishing. Already, major storms scour sediment from behind the dam, leading to giant influxes of sediment and other pollutants into the Bay during events like Tropical Storm Lee in 2011, which swept a 100-mile-long plume of sediment—visible from space—from the Susquehanna into the Bay. Although Exelon has asked for a 46-year license to continue operating the dam, the company has no plan for addressing this serious problem.

The dam is also a problem for American eels that historically made up as much as 25 percent of the Susquehanna River’s biomass. Now only relatively few eels exist in the Susquehanna River, and, of those, many cannot survive their attempt to get through the dam’s turbines as they try to return to the Sargasso Sea to spawn. The American eel is important for the ecosystem and water quality in the Susquehanna, because they are the best host for the larva of Eastern elliptio mussels that filter the river’s water, making it cleaner.

The Waterkeeper groups also plan to urge FERC to have Exelon reopen access for recreational users of the dam’s “catwalk,” which was an important part of the local heritage from 1928 to 2001. The catwalk gives access to striper fishing, the prize catch of the lower Susquehanna River. Current fishing access makes it difficult for older and disabled fishermen to reach the areas where the stripers are mostly found, over 100 feet from the shoreline fishing areas.

Case ID

2559

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