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Plan would use dredged sand to build islands near Lake Pepin

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A towboat moves a line of barges on Lake Pepin
A towboat moves a line of barges on Lake Pepin as seen from near Lake City, Minn., on May 23, 2018.
Andrew Krueger | MPR News

A plan to use sand and sediment removed from the Mississippi River to build several islands near the head of Lake Pepin is moving forward.

The pilot project proposed by the U.S. Army Corps of Engineers aims to restore backwater fish and wildlife habitat. It would also provide a use for some of the material the Corps of Engineers dredges from the river every year to allow barges to move freely.

The idea has been in the works for a few years, since the nonprofit Lake Pepin Legacy Alliance pitched it to the Corps of Engineers' St. Paul district, said Tom Novak, project manager.

"A lot of those folks who live around that area had noticed significant erosion of islands, a lot of sediment, loss of some tree species," Novak said. "So they were requesting to see if the corps could help — along with the other agencies — to restore some of that using dredged materials."

The island project is part of a larger effort to create more depth in Lake Pepin, improve game fish and waterfowl production and restore floodplain forests, said Rylee Main, executive director of the 600-member Lake Pepin Legacy Alliance.

"The communities at the upper end of the lake, where the sediment is really filling in and creating really shallow depths, have been increasingly cut off from the lake," Main said.

U.S. Army Corps of Engineers vessels are seen along the Mississippi River
U.S. Army Corps of Engineers vessels are seen along the Mississippi River just upstream from Wabasha, Minn., in October 2018. They're part of the Corps' dredge fleet for that stretch of the river.
Andrew Krueger | MPR News

The Corps of Engineers dredges the Mississippi every year to keep the navigation channel open. Putting the material back into the river to restore habitat is preferable to hauling it miles away by truck or barge, Novak said.

The Lake Pepin project will use up to 500,000 cubic yards of material already removed from the Mississippi where it's joined by the Chippewa River. It's stockpiled just north of Wabasha.

The Corps of Engineers estimates that the island project would provide an additional three years of storage capacity for dredged material. But it will not entirely solve the corps' need for space, since the agency removes about 250,000 cubic yards annually from Lower Pool 4 near Wabasha.

Novak said the Corps of Engineers has built islands in other parts of the river to restore habitat. Typically, they are a couple of acres in size, built with sand and placed over the remains of an eroded island, he said. Fine sediment is placed over the sand so trees and other vegetation can grow.

The islands help slow wave and wind energy, so the water behind the islands becomes calmer, Novak said. That helps prevent sand and sediment from becoming suspended in the river, keeping sunlight from penetrating and making it difficult for vegetation to grow, he said.

The next step is to finish the final design, which should be done by April, followed by a review period and public meetings. If the proposal is approved, Novak said he expects construction would begin in 2021.

The Wisconsin Department of Natural Resources, local cities and private donations are expected to help pay for the project, which has an estimated price range of $10 million to $20 million.

The project also has been recommended for $750,000 in Legacy funds, although legislative approval is still needed.

Main said the project is a "necessary Band-Aid" that won't fix the problem of sediment filling in Lake Pepin, which requires efforts to address land use and farming practices that cause erosion.

"We know the upstream side is really a long-term fix," she said. "In the meantime, if we don't do anything locally, we're going to lose part of the lake unnecessarily."