Michael Helfrich stands near a wall of weather-beaten concrete 10 stories tall and nearly a mile long that holds back the force of the Susquehanna River – the largest source of fresh water in the Chesapeake Bay.
Helfrich, the Lower Susquehanna Riverkeeper, explains that the Conowingo hydroelectric dam, built in 1929, has been both a curse and a blessing to the nation’s largest estuary. It blocks the passage of migratory fish upstream. But until recently, it has also been blocking about half of the soil, fertilizer and other heavy pollutants washed by rain from Pennsylvania farms and towns down into the Bay.
"The dam has accumulated about 185 million tons of sediment and pollution that otherwise would have entered the bay," Helfrich said.
Suddenly, as he spoke, a siren sounded beside the dam. "Luckily, we’re not down by the river, because there’s the alarm saying that they are going to open some more turbines and the water is going to come up," he said, as a frothing surge of water boiled and grew near the base of the dam. “That siren is the warning."
Alarms have been going off all over Maryland because of the Conowingo Dam. Some have called it a pollution "time bomb" that could rattle bay cleanup plans because the Conowingo Reservoir, behind the dam, is now just about full with sediment. The dam's days as a pollution filter are done. And so now major storms scour millions of tons of sediment – loaded with phosphorus fertilizer, as well as more exotic chemicals-- and flush them over the dam down into the bay.
The dam’s owner, the Exelon power company, has applied to the federal government to renew its operating license for another 50 years. And as part of this re-licensing process, Maryland officials have an opportunity to demand that the company make changes to better control the pollution – for example, by dredging out the sediment from behind the dam.
The amount of sediment is massive – enough to fill 243,800 rail cars, which would stretch in a line stretching 3,680 miles. More ecologically dangerous, however, is the phosphorus in the sediment, which can spur the growth of algal blooms and low-oxygen "dead zones."
It’s a significant issue – although one that some experts say is being somewhat overblown. However, whether it’s a big problem or a medium-sized one, legislation passed in December by the U.S. House, and now being debated in a conference committee with the senate, could upend the discussion. House Resolution 8 would strip away state power to impose environmental requirements on the Federal Energy Regulatory Commission (FERC), which licenses hydroelectric dams. The bill would reduce regulations for all kinds of energy producers – from gas drillers to electric utilities. Sponsor Fred Upton, Republican of Michigan, argues it’s a good idea to cut red tape for energy companies and "reduce the amount of time and money wasted in navigating unnecessary administrative obstacles." Upton added: "This bipartisan legislation has great promise for increased hydropower development, including here in Michigan."
But Maryland Governor Larry Hogan’s administration and environmentalists strongly oppose the bill, in part because it could cripple the state’s ability to solve the problem at the Conowingo Dam.
"House Bill 8 is a horrible bill that removes all of that (the states’ roles in protecting the environment around dams) and basically says the five member FERC commission will decide completely on what the relicensing will look like," said Helfrich. "It’s letting folks who were appointed out of the energy sector determine now what the energy companies are required to do to offset their environmental impacts."
Maryland’s Environmental Secretary, Ben Grumbles, said that the state is looking at a variety of possible solutions to the Conowingo sediment buildup, including the possibility of making Exelon and states upstream from the dam contribute to a cleanup.
"We will absolutely be putting some pressure on Exelon and others involved and work with our colleagues up in Pennsylvania and New York," Grumbles said.In a written statement, Exelon said it favors "regional solutions"-- suggesting it doesn’t want the finger pointed only at it.
"The resolution of the sediment issue is a basin wide issue and must be addressed as such," Deena O’Brien, Mid Atlantic Regional Communications Manager for Exelon, said in an emailed statement. "Exelon is committed to playing a role in the resolution of the issue and has demonstrated this commitment."
A 2015 report by the U.S. Geological Survey found that the dam’s sediment-trapping ability has declined dramatically over the decades. From 1928 to 1940, the dam and two others upstream on the Susquehanna (the Safe Harbor and Holtwood dams) were trapping about 6.3 million tons of sediment per year flowing down the river, which was about 70 to 75 percent off the total heading toward the bay. From 1991 to 2012, that had shrunk to 1.3 million tons of sediment per year trapped, which was only about 45 to 50 percent of the total.
A March 2016 study by the Army Corps of Engineers and Maryland Department of the Environment concluded that it is not sediment that is the biggest problem but phosphorus and nitrogen flowing down the Susquehanna River. Without the dam working as a pollution filter, Pennsylvania (which is already far behind in its bay cleanup goals) would have to reduce an additional 2.4 million pounds of nitrogen and 270,000 pounds of phosphorus pear year to meet EPA pollution limits for 2025, according to estimates in that report.
Michael Roman, director of the Horn Point lab at the University of Maryland Center for Environmental Science, said that all of the talk about Conowingo Dam being an environmental "time bomb" for the bay is exaggerated and "a bit off a distraction." A collection of rural, mostly Republican, Maryland counties has formed a group called the “Clean Chesapeake Coalition” that has been raising its voice about the Conowingo Dam as a reason for why the counties shouldn’t be forced to pay so much to reduce their own local runoff pollution to meet EPA pollution limits for the bay.
"It’s kind of kicking the can down the road, saying, 'It’s not us – it’s the Conowingo Dam," said Roman. "It’s always easiest to point at one particular entity, like that. Even if Exelon cleaned this whole thing up, in my opinion, the effect on these local watersheds where a lot of the counties sit, you would not see an improvement in water quality. Because it is local water pollution" that is harming local streams in most of Maryland.
Researchers with the Army Corps of Engineers and University of Maryland have concluded that simply dredging out the sediment from behind the dam might be both too expensive and have an environmental downside, because it would require the construction of massive new landfills.
"Just to keep up with the sediment that is coming in on an annual basis it would cost between $15 million and $270 million dollars annually for the dredging," said Anna Compton, a biologist and study manager for Army Corps of Engineers office in Baltimore. "Long term, what we were seeing from the cost and logistics …is that the water quality benefits are not there. And there are a lot of feasibility challenges with dredging at that scale, long term."
Jeff Cornwell, another University of Maryland Center for Environmental Science researcher studying the Conowingo Dam, said that moving the sediment could stir up the toxic muck behind the dam and cause more pollution problems downstream, if not handled correctly.
"The key thing is that, in moving this material, you have to deal with all of the accumulated pollutants from almost 100 years that are in the bottom of this reservoir," said Cornwell. "There are mundane things, including metals and some trace organics. There is also a little bit of radionuclide (radioactive material) from Three Mile Island (nuclear plant on the Susquehanna River) and other sources. And in moving it, you’ve got to make sure that you don’t re-suspend the material and cast it downstream."
A more pragmatic solution to a massive dredging project might be to force Exelon to pay for some limited dredging. The sediment could be re-used to manufacture lightweight cinderblocks for sale to the construction industry, so that the material would not have to be landfilled. (This is an idea promoted by the Lower Susquehanna Riverkeeper).
At the same time, as part of the relicensing process, FERC and Maryland could require Exelon and Pennsylvania to contribute money to stop sediment pollution before it ever reaches the dam. For example, the utility and commonwealth could pay farmers to build fences and plant trees along streams to reduce the flow of dirt and fertilizer downstream.
This would make sense, because it is the farmers – especially the many poorly-regulated farms that Pennsylvania has not required to keep their manure away from streams, in compliance with the state’s Clean Streams law – that are the real sources of the dam problem.
