Conowingo Dam

The Conowingo Dam is owned and operated by Exelon Generation Company, LLC and its current license expired in 2014. Exelon is seeking a new 50-year license from the Federal Energy Regulatory Commission (FERC). Under Section 401 of the Clean Water Act, the State of Maryland must issue a Water Quality Certification, certifying that the project will meet state water quality standards before FERC can grant a new license.

Waterkeepers Chesapeake has been working with Lower Susquehanna Riverkeeper and Earthjustice since 2014 to hold Exelon accountable for its fair share of the dam cleanup.

“This is our only opportunity in the next 50 years to get meaningful pollution reductions at Conowingo Dam – we have to hold Exelon accountable for its fair share of the cleanup,” — Betsy Nicholas, Waterkeepers Chesapeake Executive Director.

The State of Maryland issued its Water Quality Certification on April 27, 2018, and Exelon sued the State on May 25 in federal district court, challenging the state’s authority to require any pollution reduction from upstream sources. On July 20, 2018, Waterkeepers Chesapeake and Lower Susquehanna Riverkeeper, represented by Earthjustice, filed a motion to intervene in a federal court action regarding the relicensing of the Conowingo Dam, supporting the State’s authority under the Clean Water Act. This motion to intervene was denied.

In addition, Waterkeepers Chesapeake and the Lower Susquehanna Riverkeeper Association filed an administrative appeal on June 8, 2018, urging the Maryland Department of the Environment to reconsider its water quality certification for the Conowingo Dam arguing that is incomplete because it is missing several key elements. The State of Maryland must certify that the dam’s operations will not adversely impact water quality under the Clean Water Act. MDE has yet to address the issues in our appeal.

On October 29, 2019, MDE and Exelon announced a settlement agreement made behind closed doors that falls far short of protecting Maryland’s waterways and requires the state to waive its 401 authority to protect local water quality from impacts of dams, without any details on how the agreement will protect water quality. Affected communities and groups, including Waterkeepers Chesapeake and Lower Susquehanna Riverkeeper, were excluded from the discussions. As it is now, virtually all of the substantive portions of the settlement will not be incorporated into the 50 year federal license agreement – which means there is no public input, scrutiny and, more importantly, no ability to enforce these provisions. In addition, the settlement provides grossly insufficient funds to deal with the risks that Conowingo operations pose to the Susquehanna River and Chesapeake Bay — primarily from the next large storm that will scour the millions of tons of sediment, nutrients, and debris currently trapped behind the Dam.

Fact Sheet – Conowingo settlement

FAQs on the MDE-Exelon settlement

Fact sheet – FERC process – Conowingo

About the Conowingo Dam

The Conowingo Dam is located on the Lower Susquehanna River about 10 miles upstream from where it flows into the Chesapeake Bay at Havre De Grace, Maryland. As a hydropower dam, Conowingo has replaced a free-flowing section of the Susquehanna River with a 14-mile-long, 9,000-acre reservoir. This fundamentally alters the river’s ecology.

Ever since the dam was built in 1928, it has changed seasonal river flow; blocked the migration of shad, herring, eel and other fish; destroyed fragile aquatic habitat; devastated the shellfish communities that naturally filtered the Susquehanna’s water; killed millions of fish caught in hydroelectric turbines; and altered the river’s natural ability to transport nutrients and sediment. Nearly 200 million tons of sediment pollution have accumulated behind the dam. During major floods caused by large storms, powerful floodwaters can scoop out or “scour” the stored sediment behind the dam and send that downstream to the Chesapeake Bay. More info at

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