(ANNAPOLIS, MD)—The Chesapeake Bay Foundation (CBF) today insisted in formal comments that any new license for the operation of the Conowingo Dam on the Susquehanna River require the dam's owner to reduce the risk of sediment and nutrient pollution releases, and to improve passage for migratory fish.
"Sediment is building up behind the Conowingo Dam, and large storms will most certainly scour large volumes of this dirt, and associated nutrient pollution, resulting in effects on water quality downstream in the Chesapeake Bay," said CBF Senior Scientist Dr. Beth McGee.
Since its construction, the Conowingo dam has been trapping sediment and sediment-associated phosphorus in the Conowingo reservoir. As such, the dam has acted like a giant pollution filter, safeguarding the Bay from large amounts of dirt and phosphorus pollution flowing down the Susquehanna from farms, city and suburban streets, and other sources.
However, researchers estimate the reservoir is almost completely filled and, as a result, has lost much of its capacity to trap and store sediment and phosphorus. Furthermore, large storms will scour sediments from behind the dam. Nitrogen, phosphorus and sediment will spill through the dam to the Chesapeake Bay.
In September 2011, U.S. Army Corps of Engineers, Maryland Department of Natural Resources, Maryland Department of the Environment, the Susquehanna River Basin Commission, and The Nature Conservancy announced the launch of a three-year feasibility study to devise solutions to the sediment management problem. The study is scheduled to be finalized by fall, 2014, with preliminary findings possibly released earlier. It will offer cost estimates as well as possible solutions.
In its comment letter, CBF requested that the Federal Energy Regulatory Commission use the results of this study to develop the new license for Exelon Corporation, the owner and operator of the dam.
CBF also insisted in its formal comments that fish passage be improved at the dam. CBF is concerned with the restoration of migratory fish to the Susquehanna, specifically American shad, hickory shad, American eel, Atlantic sturgeon, shortnose sturgeon, alewife and blueback herring. Improving upstream and downstream passage for these migratory fish is essential to their recovery from current historic low levels. These migratory species once supported valuable fisheries in the Chesapeake Bay and its tributaries, but, with the exception of American eel, all are currently prohibited from harvest in the watershed.
CBF recommended a number of structural and operational changes at the dam to improve fish passage sufficient to meet restoration goals for these species. Both existing fish lifts should be upgraded, a new passageway for eels must be built, and water flow must be better managed to provide suitable aquatic habitat downstream. Eventually, CBF recommended, the efficiency of the dam to pass shad and herring as they move upstream to spawn in the spring must increase to 85% from the roughly 20% currently being achieved. 95% of juvenile shad moving downstream in the fall must pass the dam successfully.
"The public can rest assured we have our eyes on this process, as do many other watchdogs. Given that the life of the new permit will be 46 years, it is imperative we get the best deal possible for the environment," McGee said.