What's the Impact of Dumping Dredged Waste in Long Island Sound? | Connecticut Public Radio

What's the Impact of Dumping Dredged Waste in Long Island Sound?

Jan 27, 2016

Millions of tons of sediment and sand could be dumped into the open waters of Long Island Sound in the coming decades. That’s according to a recently-unveiled federal plan outlining what to do with materials dredged from the bottoms of coastal ports and harbors.

Why do our port bottoms keep filling up with stuff like sand and glacial sediment? Put simply: if nature sees a hole -- it’s going to fill it.

"Dredging is done because many harbors are naturally quite shallow," said George Wisker, an environmental analyst with the state Department of Energy and Environmental Protection.

In the old colonial days, Wisker said, shallow draft boats could navigate state waterways with little problem, "but as ships got bigger and bigger, there became a need to create channels for them to get into the harbors and get out again," he said.

Thus, dredging -- a fancy word for cleaning up harbor beds, which need to be free and clear of debris for boats to get through.

For decades, it's been a crucial part of the mission of the U.S. Army Corps of Engineers, which is involved in lots of coastal dredging projects on Long Island Sound. Last month, the group released its plan for how to manage an estimated 50 million cubic yards of material. It plans to dredge from marine bottoms over the next 30 years and its plan is generating some controversy among environmentalists.

A schooner in front of Radel Oyster Co., South Norwalk, early 1900s.
Credit Mystic Seaport / Connecticut History Illustrated

Rain, Currents, And Lots of Moving Sediment

Before we talk about that controversy, how does all that sediment get there to begin with? "It’s really difficult to say, 'A-ha!' Definitively, this amount is coming from this source and this amount is coming from another,'" Wisker said.

But scientists have ideas. One answer, Wisker said, lies in erosion. Upstream sediment gets knocked loose during a heavy storm and flows into a river like the Connecticut, making its way downstream until it reaches Long Island Sound. "And when the current stops the sediments will settle out," Wisker said. "Depending on the size of the harbor, the amount of tides, do we have any big storms -- you can get significant amounts of sediment."

Nothing illustrates this process better than a 2011 NASA satellite photo taken after Hurricane Irene. That heavy rainfall kicked up lots of upstream sediment -- and viewed from space, it looks like silky chocolate milk spewing into Long Island Sound from the mouth of the Connecticut river.

Nearly a week after heavy rainfalls from Hurricane Irene in 2011, the Connecticut River spewed muddy sediment into Long Island Sound.
Credit NASA Earth Observatory

"That was incredible," said Wisker. "It was a great example showing how much Mother Nature can really move this stuff around."

Long Island Sound currents can push sediment into harbors as well. James Tait, a professor of marine and environmental sciences at Southern Connecticut State University, said to picture a room with a ray of sun shining through the window. And the sediment is like dust floating in the air. "They're like dust motes," Tait said. "You know how they just float and float and float?"

Like dust, sediment needs to find a quiet environment in order to deposit itself -- and harbors are ideal. "If you were in a room and you were looking at dust motes," Tait explained, "you'd probably leave the room, close the door and seal the door and wait for a week or something like that." 

Coastal marshland can act the same way, so when the Army Corps of engineers dredges all this stuff up -- you can probably anticipate the next question: Where does it go? That’s where some environmentalists get riled up.

Credit slack12 / Creative Commons

Once Dredged, To Recycle Or Dump?

"Hey, we’re not against dredging. We totally understand and want dredging to continue in both New York and Connecticut," said Adrienne Esposito, executive director of Citizens Campaign for the Environment, an advocacy group in New York and Connecticut. "It’s very important for access to the waterways, for navigating our waterways -- we get it," she said. "Simply, what we are saying is let’s begin a new way of dealing with these dredged materials that’s safer, cleaner, and more environmentally responsible."

Dredged sediment can have a lot of uses. It can be recycled as sand or sediment to re-build beaches or coastal marshes battered by climate change. It can be de-watered and put in a landfill, or it can get deposited into the open ocean. But the kind of heavy metals and chemicals found in that dredged material worries Esposito, which means before a harbor floor gets dredged, scientists need to ask a really basic question: is it polluted?

"The public has to hold the Corps’ feet to the fire to make sure they do not violate any of the criteria associated with disposal in Long Island Sound," said Larry Swanson, an oceanographer at Stony Brook University who studies marine pollution. 

A representative from the Environmental Protection Agency said most dredged material isn't contaminated. But some is, thanks in part, to our state's industrial past, back when Connecticut companies made products using chemicals with environmental impacts not fully understood at the time.

Hats in the various stages of manufacture from the “raw material” to the finished product. Mercury was often used in hats produced in Danbury.
Credit J. Moss Ives, 1901 / Connecticut History

"When Connecticut was largely involved in the jewelry industry, in the hat industry, and other industries," Swanson said.

That history left behind a chemical legacy of heavy metals embedded in some coastal bottom sediment. George Wisker from the state DEEP said it also left industrial waste, "which are known as PAHs and PCBs, and also pesticides," he said.

For that reason, the U.S. Army Corps of Engineers said any dredged material proposed for open-water disposal will have to pass "stringent testing requirements."

As Wisker explained it, before dredging even begins, that means taking core samples. "The federal projects also have to automatically undergo biological testing," he said, "where they're put into aquaria with certain very sensitive minnows."

That's to see if harbor-sediment kills the fish. If it doesn't, Wisker said, the core samples are then put into other tanks for "bioaccumulation tests."

"Where they sit for about a month and then the survivors in there are analyzed for if they uptake any of the materials, the bad constituents," he said, "and if they did, to what level."

If the sediment is contaminated, Wisker said options are limited. The harbor either won't get dredged or its materials will be dug up, buried deeper in the harbor, and capped with clean sediment. Kind of like an underwater landfill.

If it's clean -- the Corps said the dredged material is fair game for open water disposal. But even if it's relatively pure, could dumping tons of sediment on Long Island Sound ocean bottoms still have long-term ecological impacts?

A map of active dredged materials open water disposal sites in New England.
Credit U.S. Army Corps of Engineers

Scientists like Wisker and Stony Brook’s Larry Swanson don't think so. Neither does James O’Donnell, a professor of marine sciences at UConn. "It’s pretty settled, as far as I can see, that’s there’s really no adverse impact that’s been documented from the disposal of reasonably uncontaminated sediments in Long Island Sound or anywhere else," he said.

But environmental groups still say they’re frustrated by the Corps lack of vision in dealing with disposed materials. "Dredged materials should be looked at as a resource and not a waste material," said Adrienne Esposito from Citizens Campaign for the Environment. She and other groups like Save the Sound want to see a greater push for re-use of dredged materials in habitat restoration and coastal resiliency projects.

Esposito said she’s also worried about how ocean currents could move sediment when placed in open water. "It’s all different sized sediment and it’s all different sized grains. It’s all different constituents," she said, "it doesn’t go straight down."

Credit m01229 / Creative Commons

While some drift is unavoidable, DEEP’s George Wisker said scientists have identified specific Long Island Sound drop zones -- and that sediment is dropped on different areas of those zones at different times using GPS.

Much like a farmer cycles his fields season-to-season to let soil rest, Wisker said rotating the drops lets ocean-floor life re-develop.

Larry Swanson at Stony Brook said when you look out at Long Island Sound in 30 years, you’re not going to see anything different because of dredging. "Sea level rise is going to be a much bigger problem for us in the next 30 years in Long Island Sound than anything that we’re putting in from this dredged materials disposal plan," he said.

The EPA now has until later this year to rule on whether it will re-authorize the use of certain disposal sites in Long Island Sound.

Gabrielle Fonrouge from member station WSHU contributed reporting.