A year ago, Gov. Larry Hogan put out a call for private industry to suggest how Maryland should address the pollution that was quickly piling up behind the Conowingo Dam — a staggeringly expensive problem that many policymakers thought could wait.
For nearly a century, the dam had stopped silt and polluting muck in the Susquehanna River from spilling into the Chesapeake Bay. There was wide agreement the reservoir behind the dam would eventually reach its capacity, and stop holding back the pollution.
But scientists now agree the dam is not stopping anything at all.
"I wouldn't so much say it's worse than we thought," said Robert M. Hirsch, a research hydrologist with the U.S. Geological Survey. "It's come upon us sooner than we thought it would."
When Hogan requested proposals last August, the U.S. Army Corps of Engineers' most recent estimate to dredge the reservoir of 25 million cubic yards of silt stood at $3 billion. That was way too high for the state to undertake the job alone and, some argued, more money than should be spent on a problem that scientists say isn't the largest source of pollution flowing to the bay.
It also didn't address the roughly 3 million additional cubic yards of silt that flow down the river every year, mostly from Pennsylvania and New York.
Now, the scientific consensus that the dam is not holding back any pollution has given Hogan ammunition to forge ahead.
The Republican governor says he's about to announce a plan to make "some real progress" at the dam, based on some of the proposals the state received.
He says he will seek a contractor next month to deal with the sediment and dissolved phosphorous and nitrogen pollution that weakens the bay's health. And he'll convene a summit to discuss what he wants to do.
Hogan promised to address the dam during the 2014 campaign.
"Most people didn't seem to agree that it was a problem," he said. "Now everyone seems to agree that it's a problem."
A dozen companies responded to Hogan's call for innovative ideas to save money on the project, according to a review of public records obtained by The Baltimore Sun.
Arcadis, based in the Netherlands, suggested buying 2,400 acres of low-quality agricultural land, smearing it with the nutrient-laden sediment and selling it for a higher price. Immix, a Colorado firm, pitched a physics process advertised as using earthquake-strength forces to compress the sediment into pavers and countertops that could be resold at a profit.
Brinjac Engineering, headquartered in Pennsylvania, suggested a two-mile long "biological dredging" operation that would use microbes on the river bottom to chew through sediment, cleaning the water and reducing how much needed to be dredged in the first place.
The firm estimated it would cost about $23 million and take five years to deal with just 1.5 million cubic tons of material, but said it could generate pollution credits Maryland could sell to other states that haven't done their share in cleaning up the bay.
Donge Flushing Yard, also based in the Netherlands, offered to build Maryland a custom dredging boat for 18 million euro — about $20.6 million — to pull up muck 24 hours a day and then dump it in the ocean. Once the state owned the boat, the operation would cost $52,000 a week just to bring the material ashore.
The boat could be resold, the firm said, for about 70 percent of its initial price.
Harbor Rock, headquartered in New Jersey, said that for $100 million a year, it would dredge up the gunk and build a processing plant to feed it through 2,000-degree kilns, which would turn it into a material that can be used to make concrete.
The firm said it would need about three years to get the operation moving, could deal with 2 million cubic yards per year, and would keep the profits.
Cold Harbor, another Colorado company, offered a mobile sediment processing system that could quickly set up in an existing parking lot. It said sand from smaller projects has been used to make boat slips in South Carolina, agricultural topsoil in Indiana and berms at a Florida gun range.
Hirsch, the hydrologist, wrote some of the first papers suggesting the problem couldn't wait another 15 years. But he qualified the urgency.
Although the Susquehanna River is a major contributor of nutrient pollution, he said, much of it flows into deep areas of the bay that aren't as ecologically sensitive. Lower amounts of pollution in shallower and more fragile areas can have a bigger overall impact on bay health.
While there's wide consensus the Conowingo reservoir is now full, Hirsch said, not everyone agrees on how quickly there needs to be a solution, nor what it should be.
"There's consensus about the nature of the problem," Hirsch said. "There needs to be a lot more analysis of these alternatives."
Hogan said he also plans to lean on the federal Environmental Protection Agency and use his chairmanship of the Chesapeake Executive Council to make states upstream of the Conowingo — Pennsylvania and New York — take more responsibility for pollution that's now cascading over the dam.
Sediment scours the waterways. But the bigger problem, scientists say, is the release of nitrogen and phosphorus it brings with it. An abundance of those nutrients kicks off a cycle that harms the bay: the nutrients feed algae blooms that block light and kill underwater plants, which in turn depletes oxygen in the water, choking fish and other wildlife that help keep the bay clean.
While the administration declined to offer details on the request for proposals the governor will issue, Environment Secretary Ben Grumbles pointed to a road map the state released this year on beneficial ways to use sediment dredged out of the waterways.
That plan, Grumbles said, helps make dredging projects more affordable. Sediment brought up from the Chesapeake can be reused to build roads, restore eroding shorelines, or cap landfills — aftermarket uses that make the sediment a valuable commodity, rather than just expensive waste.
"We're gaining momentum on the Conowingo challenge," Grumbles said.
He also said it was "short-sighted" to view dredging as the entire solution to the problem. He touted the benefits of creating a marketplace to sell and trade pollution credits, an initiative the administration pitched unsuccessfully to the General Assembly this year.
Grumbles said the state also plans to use any regulatory leverage it has to force others to help cut pollution before it gets into the watershed and pay to remove it from the reservoir dam. Among those tools: Hogan's ability to effectively veto Exelon energy's bid to renew its license to operate the hydroelectric dam.
Under federal laws, the governor has the authority to halt relicensing of the dam if he does not believe it adequately meets the state's clean water standards.
Hogan said the company has "got to be part of the solution, but it would be crazy to expect them to do the whole thing."
A spokeswoman for Exelon said the company already is working with the government and others.
"Exelon Generation believes protecting the vitality of the Bay is a multi-stakeholder, multi-state issue," spokeswoman Deena O'Brien said in a statement, "and we continue to work with all parties, including Gov. Hogan and his administration, to ensure the Lower Susquehanna River retains its important environmental and recreational benefits."