Who Should Be Responsible For the Conowingo Dam’s Pollutant Loads?

A Bay Journal article  (2016-12-08) examined the challenging question of addressing the Conowingo Dam as part of the Chesapeake Bay restoration efforts. As previously reported on Conduit Street, research has shown that the Dam’s reservoir is full and no longer trapping sediment or nutrients as it has for decades. Instead, the Dam has reached a state of “dynamic equilibrium” where sediments and nutrients going into the Dam reservoir now pass on into the Bay. As part of the 2017 midpoint assessment of the Bay Total Maximum Daily Load (TMDL) review, federal and state authorities are trying to determine who should be responsible for addressing the Dam’s unanticipated loading. From the article:

“It’s probably the decision that will be the most challenging to the partnership because it is potentially so divisive,” said James Davis-Martin, Bay coordinator with the Virginia Department of Environmental Quality and chair of the Bay Program’s Water Quality Goal Implementation Team. “It can set the us-against-them mentality in place.” …

“The free ride is over,” said Robert Hirsch, a USGS research hydrologist whose work a few years ago was the first to show the dam was starting to leak more nutrients downstream. “What comes in basically goes out under the current situation.”

The article examined the tricky issue of assigning responsibility for the Dam’s additional and unanticipated pollutant load, noting that the United States Corps of Army Engineers has estimated that 9% more nitrogen (2.4 million pounds annually) and 38% more phosphorus (270,000 pounds annually) must be reduced between now and 2025.

In an appendix to the TMDL, the [United States Environmental Protection Agency (EPA)] said that if the Conowingo reservoir did fill prior to 2025, it would consider assigning steeper cuts to areas of Pennsylvania, Maryland and New York upstream of the dam to make up the difference.

But some question whether that is fair, or realistic. Pennsylvania — which would bear the brunt of any additional reductions — is already lagging far behind in its cleanup. It needs to ramp up the pace of nitrogen reductions five-fold beyond recent efforts just to meet current goals. …

“We have collectively reaped the benefits of the reservoir and its trapping capacity, and maybe there is a reasonable expectation that we share the consequence of that trapping capacity being lost,” Davis-Marin said. …

If the dam’s fading benefit had been recognized in 2010, [Chesapeake Bay Foundation Senior Water Quality Scientist Beth] McGee said, those additional nutrients would have been divided across the watershed using [the original nutrient allocation] formula. …

Under that scenario, areas upstream of the dam would still have to undertake the greatest action — because they have the greatest impact — but some of the burden would be spread among other jurisdictions.

The article explained that some have proposed a hybrid approach to addressing the Conowingo’s nutrient loading, where reductions are undertaken in the jurisdictions that can carry them out most cheaply but that financial responsibility for the reductions be shared jointly by all Bay watershed states. However, the article noted that such an approach has its own challenges:

Though enticing in theory, that option is unlikely. Right now, Bay Program officials say the tools do not exist to support such decisions. And even if they did, most are skeptical that politically, states would willingly send their cleanup money elsewhere. All states still have substantial work to meet their own TMDL goals — reductions necessary to not only meet Bay water quality goals, but also those within their own tributaries.

“Would downstream states…really send money to areas that are doing more because it is more cost-effective?” McGee asked. “I don’t think so, especially if it means money going out of the state.”

Some have also proposed addressing the Conowingo offsets after 2025 but the article stated that any extension of the 2025 deadline was a “non-starter” with EPA. The article also noted that climate change and under-estimated phosphorus loading from animal farming may further complicate the problem by requiring additional nutrient reductions similar to those required to the Conowingo. Finally, none of the proposed reductions deal with the Dam’s significant sediment and nutrient discharge problem during severe weather events:

Indeed, other factors will also pose challenges. Preliminary estimates suggest that offsetting the impacts of climate change on Bay water quality by 2025 might require a level of nutrient reductions similar to those needed to offset Conowingo’s lost trapping capacity. Also, additional phosphorus reductions are likely to be needed in parts of the watershed because more of that nutrient is leaking from soils than previously thought in areas with intense animal farming. Population growth and development will produce more nutrient pollution as well. …

The debate among policy makers over how to adjust the cleanup effort for the Conowingo’s lost nutrient trapping capacity does not directly deal with one issue: the potentially devastating impact of extreme weather events. Tropical Storm Lee in 2011, and the even more severe Tropical Storm Agnes in 1972, sent water, nutrients and sediment flooding into the Bay, in the process scouring huge amounts of those pollutants from behind the dam. With the Conowingo reservoir now essentially filled, even more material is available to be flushed into the Bay.

Useful Links

Prior Conduit Street Coverage of the Conowingo Dam