Conowingo Dam cleanup should require specific measures

Over the weekend, about 800 people took a tour of the dam and adjacent power plant during Exelon Generation's third annual open house. (David Anderson and Dan Griffin, Baltimore Sun Media Group)

When planning for an emergency, you generally plan for the worst-case scenario. Ships need to carry enough life boats for every passenger, not just a few. Fire regulations call for smoke detectors in every bedroom, not just one per floor. Vehicle safety ratings are tested for full-speed collisions, not just fender-benders.

We should expect the same for environmental regulations. Unfortunately, a recent decision by the Maryland Department of the Environment concerning the Conowingo Dam does not follow the same rationale.


The dam, at the mouth of the Susquehanna River near Havre de Grace, is owned and operated by Exelon Corporation. Exelon uses the dam to generate electricity from the river at a profit. The dam was completed in 1928 and has been trapping sediment and nutrient pollution from the Susquehanna and its 27,000-square-mile drainage area ever since.

Challenge of Conowingo sediment hasn't changed much - nor have the misleading claims.

The reservoir behind the dam is now basically at capacity — it cannot trap any more sediment. This is a problem because when it rains, runoff pollution from the largely agricultural area upstream from the dam makes its way into the river and ultimately the Chesapeake Bay. Even more problematic is the potential for "scour," where powerful floodwaters can actually scoop out the stored sediment behind the dam and send that downstream to the bay.


Exelon has requested a new 50-year federal license to operate the dam. In order to receive it, the State of Maryland must certify that the dam's operations will not adversely impact water quality under the Clean Water Act. The state has been deliberating on the certification for several years.

On April 27, the Maryland Department of the Environment announced that it had issued its water quality certification for the Conowingo Dam. The certification acknowledges the impact of the dam on water quality, including the threat posed by the accumulated sediment. And while there are admirable goals, the certification only requires Exelon to adopt a "nutrient corrective action plan" rather than put specific measures in place.

Md. environment secretary: Under Gov. Larry Hogan’s leadership, Maryland is living up to its strong commitment to environmental protection and climate change progress — and to protecting the health of our citizens.

We believe that the Clean Water Act requires the dam's operator to do more than promise to reduce pollution. It requires concrete conditions that will ensure there is no adverse impact to water quality.

And in order to do that, Maryland must understand the full potential of large flooding events, which could cause dramatic harm to the bay. Shockingly, to my knowledge, there has been no modeling or study conducted of how much sediment pollution would be scoured from behind the dam during a "50-year" storm, even though the new license will be nearly that long. Even more surprising is that there hasn't been a study of a 25-year storm, which has an 83 percent chance of occurring during the license period.

Neither do we have an appropriate understanding of how a scouring event will affect critical natural resources like underwater grasses. Recently, the Virginia Institute of Marine Science announced that its annual survey of underwater grasses recorded the highest acreage since the survey began in 1979.

Maryland environmental regulators are requiring the owner of the Conowingo Dam to find a way to limit pollution that flows down the Susquehanna River from reaching the Chesapeake Bay, because the structure is no longer effectively trapping the sediment and nutrients washing down from Pennsylvania.

The uptick in underwater grass is a great indicator that the bay is improving due to the many regulations and best practices that have been enacted in the last several decades. And we certainly don't want to jeopardize that progress by failing to plan for a large scouring event from Conowingo.

Exelon makes a profit by generating electricity using the power of the Susquehanna River, a public resource. Public resources deserve protections. If Maryland wants to position itself as an environmental leader, here is a chance to prove it.

We cannot afford to give Exelon a new, 50-year license without specific, measurable conditions that ensure its operations do no more harm to the Chesapeake Bay. Therefore, the Maryland Department of the Environment should include a requirement to dredge some portion of the accumulated sediment and nutrient pollution stored behind the dam as a condition of its water quality certification for the new license. We also call upon MDE to properly account for the damaging effects of large storm events during the new license period.

To achieve the best results, we must plan for the worst. The Chesapeake Bay deserves a good emergency plan.

Betsy Nicholas (betsy@waterkeeperschesapeake.org) is executive director of Waterkeepers Chesapeake. Ted Evgeniadis is the Lower Susquehanna riverkeeper.

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