State says pilot project to collect, test dredge material from Conowingo Dam will be completed this year

Conowingo Dam
Conowingo Dam (Kim Hairston / Baltimore Sun File)

Maryland officials said Monday they expect a pilot project to test removal of dredge materials from Conowingo Dam to be “substantially complete” later this year.

A buildup of nutrients and sediment behind the dam, washed into the Susquehanna River from across Pennsylvania and upstate New York, is considered a significant threat to progress at cleaning up the Chesapeake Bay. Dredging has long been considered vital to counteract that risk, but also potentially too expensive to be feasible.


Northgate Dutra Joint Venture, a firm with offices in Frederick, was selected in late 2017 to carry out a $3 million pilot project to test sediment in the Conowingo reservoir and dredge a small portion of it to determine a possible reuse and market for the materials. Officials said the project is being paid for through the Maryland Department of the Environment, in conjunction with the Maryland Environmental Service and the Governor’s Bay Cabinet.

The Conowingo Dam stretches across the Susquehanna River between Harford and Cecil counties, and opened in 1928 to generate hydroelectric power. Since then, it has been holding back some sediment, which can cloud water and smother underwater grasses that serve as habitat for aquatic life, and nutrients, which contribute to algae blooms that suck oxygen out of the water.

Roy McGrath, director and CEO of the Maryland Environmental Service, said the pilot project will “aid in identifying and ultimately reducing contaminants in the reservoir behind the hydroelectric dam, preventing those from flowing downstream, and leading to continued improvements in water quality throughout the Chesapeake Bay watershed.”

A state presentation last year suggested the dredge material could be used as landfill cover, fill material or to help stabilize shorelines.

Government officials, dam owner Exelon and environmentalists have sought ways to address the Susquehanna’s sediment pollution as it has become clear it can no longer trap the material. In summer 2017 Gov. Larry Hogan announced the creation of the pilot project to study solutions.

Officials have said in the past that there was about 31 million cubic yards of sediment lodged behind the dam; the pilot project calls on Northgate-Dutra Joint Venture to dredge 25,000 cubic yards of material.

Monday’s announcement of a 2019 completion date came as the Hogan administration touted what it called “significant progress toward solving environmental problems stemming from the Conowingo Dam.”

The state noted that it is working with the U.S. Environmental Protection Agency on a multi-state plan to reduce the amount of nutrients and sediment that wash into the Susquehanna upriver of the Conowingo, but that the dam can no longer trap.

Exelon Corp. is seeking a 50-year federal license renewal for the dam’s operation, and as part of that process, last year the Hogan administration required the company to do more to prevent pollution from passing the dam. Exelon has challenged those requirements in U.S. District Court. MDE has filed a motion to dismiss the complaint.

Baltimore Sun reporters Scott Dance and Pamela Wood contributed to this article.