A Baltimore Sun article (2017-07-16) reported that in light of research questioning whether the Conowingo Dam is trapping any nutrients or sediment flowing into the Chesapeake Bay through the Susquehanna River, Maryland Governor Lawrence “Larry” Hogan has redoubled his search for a private contractor to address the problem and will convene a summit to discuss next steps. As previously reported on Conduit Street, Hogan requested proposals for addressing the sediment build-up behind the dam last year. According to the article, Hogan has received a dozen responses:
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. …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. …
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. …
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. …
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.
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.
Useful Links
Conduit Street Article on Recent Conowingo Dam Research
Conduit Street Article on Hogan’s Original Conowingo Announcement
