Twin Ports harbor project aims to restore habitat for wildlife with dredged material

For decades, the U.S. Army Corps of Engineers has dredged sand and muck from the Twin Ports harbor to keep shipping channels open. Now, it plans to put some of that material back.

The Corps is seeking comments on a plan to use 300,000 cubic yards of dredged materials to convert the 21st Avenue West Channel Embayment into a wetland. The project would have the twin benefits of restoring habitat for wildlife while eliminating the need for on-shore disposal of the dredged material.

“We think it fits really well with a long-range plan to reuse material dredged from the channels for habitat restoration,” St. Louis River Alliance executive director Julene Boe said. “It is a good thing.”

The alliance is one of several groups working to improve the environmental health of the Lower St. Louis River. Their goal is to have the area delisted as a federal Area of Concern.

“The 40th Avenue West complex is another area (where) restoration folks are looking at how we can plan for habitat restoration,” Boe said.

In October 2011, the federal Great Lakes Interagency Task Force committed to accelerate cleanups of contaminated rivers and harbors to delist Areas of Concern. Late last week, the U.S. Environmental Protection Agency announced that Presque Isle Bay, on the Pennsylvania shore of Lake Erie, has been removed from the list. Presque Isle Bay’s delisting reduces the number of Areas of Concerns to 29 contaminated sites wholly in the U.S. or shared with Canada.

The planned 21st Avenue West pilot project would place 300,000 cubic yards of material into 18 to 20 acres of the 21st Avenue West Channel Embayment over three years. Water depths in the area range from 3 to 24 feet. The goal is to reduce those to 1 to 10 feet, allowing both submerged and emergent plants to take root — creating valuable habitat for a variety of plant, fish and wildlife species.

“The lower reaches of the St. Louis River are lacking vibrant submergent and emergent wetlands, which are important to the overall biological and ecological diversity of the St. Louis River estuary,” the Corp’s environmental assessment said.

The Minnesota Pollution Control Agency and the Corps will monitor the pilot project’s success to help determine whether it can be used at other sites.

“We are looking at how this material will create vegetation,” said Terry Long, chief of the Corps’ district plan formulation branch.”

“We look at this as baby steps, because long-term there are a large number of sites called areas of concerns,” he said. “If our dredged material will create vegetation, we can look at using the same material at other sites.”

In addition to creating valuable wildlife habitat, placing dredged materials in unused channels and other areas would solve the problem of how to dispose of it.

“This is really a win-win project for the economy and environment,” Corps operation project manager Mollie Mahoney said.

The Corps dredges 100,000 cubic yards a year from the harbor to keep channels sufficiently deep for shipping. The bulk is brought to the 80-acre Erie Pier site, which is owned by the Duluth Seaway Port Authority and operated by the Corps. At Erie Pier, the material is separated into sand and “fines,” which contain clay and organic material. The materials are routinely tested to ensure they’re safe.

The Port Authority has little problem finding markets for the 20,000 to 50,000 yards of sand dredged annually. But there are about 2 million yards of fines stockpiled at Erie now. Finding uses for the material — both what is stockpiled and what comes in each year — is vital to keeping Erie Pier in operation. The alternatives would be to build a new facility elsewhere or to increase Erie’s capacity by increasing the height of its dikes.

To avoid the costs of expansion, the Port Authority is working to develop markets for fines. It’s very excited about the idea of using dredged material to create wildlife habitat, said facilities manager James D. Sharrow. He sees great potential for using the stockpiled fines for restoring aquatic habitats.

“With about 2,000 acres of near-shore shallow bays that could be restored, it has the potential to basically empty Erie Pier,” he said. “Fines have very good properties for growing vegetation that is needed in a flourishing habitat.”

For this pilot project, the Corps will use unsorted material. The Corps plans to award a contract in May for the first year’s work, which would begin in June and continue until September or October. The work is expected to cost between $1 million and $5 million.

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