New 50-year Conowingo Dam license gets federal OK, but environmental groups worry it won’t do enough to stop pollution overflows

A new 50-year license for the Conowingo Dam recently received a key federal approval, but environmental groups called the agreement a missed opportunity to compel Exelon, which runs the hyrdoelectric dam, to do more to stop pollutants flowing down the Susquehanna River and into the Chesapeake Bay.

The dam, which spans Harford and Cecil counties and can generate 572 megawatts of electricity, had long trapped pollutants and debris, stopping them from flowing down the river and emptying into the bay near Havre de Grace.


But sediment has filled in much of the reservoir behind the dam, so when storms cause flooding, pollutants can overflow.

In 2018, the Maryland Department of the Environment, through a water quality certification, required Exelon to develop a plan to reduce nitrogen and phosphorus pollution in amounts equal to what had been trapped previously. Or, state regulators said, the power company could pay an annual fee — $17 per pound of nitrogen and $270 per pound of phosphorous — totaling $172 million per year.


But the following year, the state reached a settlement with Exelon that required the dam operator to commit a total of $200 million to projects aimed at cleaning the trash and debris passing through the river, increasing grass and oyster plantings, and studying the sediment issue.

 A new 50-year license for the Conowingo Dam got key federal approval last week, but environmental groups say the agreement is a missed opportunity to compel Exelon, which runs the dam, to do more to stop pollutants flowing down the Susquehanna River and into the Chesapeake Bay. March 23, 2021

Environmental groups are concerned because the dam’s new license, issued March 19 by the Federal Energy Regulatory Commission, cements that settlement, and does not add requirements focused on reducing nutrient overflows — or paying for them.

The federal agency found that dredging the reservoir and relocating the sediment could prove prohibitively costly and be rendered ineffective by the continued flow of sediment from upstream.

The company had argued that the pollutants flowing down the Susquehanna, largely from sources in Pennsylvania, aren’t its responsibility. But studies show the dam changes the timing of when pollutants are released and the characteristics of those pollutants.

For instance, rather than flowing at a steady rate, pollutants are discharged all at once when the floodgates open.

Conservationists worry that a substantial, hurricane-caliber storm could force the dam to dump considerable nutrients and sediment downstream, covering underwater grasses and oyster beds, and contributing to the growth of harmful algae blooms that suck up oxygen and block sunlight.

“It’s kind of like a great big ice cream scoop comes and scoops up the sediment and dumps it downstream,” said Betsy Nicholas, executive director of Waterkeepers Chesapeake. “There’s a really big concern that it could take, you know, decades to recover from that kind of storm.”

Storm debris gathers March 23 at the northwest corner of the Conowingo Dam.

And with climate change, storms are expected to become more intense.


“Knowing about situations like Ellicott City — you know, thousand-year storms two years apart — we should be planning, knowing that we’re probably going to get a big storm in there over the next 50-year license term,” Nicholas said. “And yet, that isn’t taken into account here.”

As part of the settlement between Exelon and the Hogan administration, which was approved by the FERC, Maryland also waived its right to issue a water quality certification for the dam.

For activists, it sets a concerning precedent. The certification would allow Maryland to set a series of requirements for Exelon as it did in 2018.

“When a state issues the water quality certification for a project, it says: ‘You were causing this harm in order to operate, you need to mitigate these things, or you need to operate X, Y and Z ways to not cause harm,’” said Alison Prost, vice president of environmental protection and restoration at the Chesapeake Bay Foundation.

There are, however, favorable aspects of the license approved by FERC, Prost said, such as the programs to promote mussel restoration, fish and eel passage, turtle management and waterfowl nesting. But, she said, in addition to the measures for wildlife, stronger measures focused on water quality were necessary.

“Both were needed, and only one solution was included in the settlement,” Prost said.


The settlement does require Exelon to monitor dissolved oxygen levels about half a mile downstream, and monitor for fish kills that could result. It also compels that the company clean up at least as much trash and debris from the Conowingo Reservoir as it did in 2018, a year of intense rainfall.

The measures in the settlement are “a win for Maryland, the environment, and the economy,” wrote Deena O’Brien, a spokesperson for Exelon, in a statement.

The dam produces enough electricity to power 165,000 homes, according to Exelon.

“These benefits would not have been achieved without a settlement agreement that resolved significant legal challenges to the water quality certificate that MDE issued in 2018,” O’Brien wrote.

Exelon had argued that MDE didn’t have the authority to require the nutrient reductions.

MDE dubbed the licensing “encouraging news for the Susquehanna River and the Chesapeake Bay after almost a decade of gridlock.”


The dam’s old license expired in 2014, and it’s been operating under annual licenses since then.

“We are also committed to taking additional actions, such as the multi-state Conowingo Watershed Implementation Plan, to do even more to prevent upstream pollution and reduce the risks from the lost trapping capacity of the Conowingo Dam,” said Maryland Secretary of the Environment Ben Grumbles in a statement.

But Zack Kelleher, riverkeeper for the Sassafras, a Chesapeake Bay tributary south of Conowingo, called FERC’s particularly disappointing given the number of groups that advocated for stricter provisions.

“We made our voices heard and we had town halls and we had legislation and we met with local towns and communities,” Kelleher said. “And the state still chose ... the profit margins of a corporation over the will of its own citizens.”

Parties can ask that FERC reconsider the license, or take the matter to federal court, said James Pew, an attorney for Earthjustice.

Either way, environmental groups will continue to seek funding for projects to reduce the pollution flowing into the river, Nicholas said, like planting forest buffers along its banks.


“It’s such a huge missed opportunity here that, you know, what I’m really afraid of is that 5-10 years down the road, we’re going to be looking back at this and thinking: What happened?” Nicholas said. “How did we let this go through?”