To protect Mississippi River dam, Army Corps may build an island near Hastings

Decades of ice and wind blowing uninterrupted for miles along the Mississippi River have eaten away at the embankment of the lock and dam in Hastings.

But rather than reinforce the gravel and dirt that have held up the structure since the 1930s, only to see it wash away again, the Army Corps of Engineers wants to try something new: Build an island.

The 40-acre island would be built just upstream of the dam with the sand and mud the corps dredges out of the lock to keep it open for navigation. It would act as a windbreak, taking the worst the river can throw at it while leaving calmer waters and more gentle ice downstream, said Nick Castellane, project manager for the corps.

"This island is an interesting idea because the wind fetch at the site is up to 3 miles — that's 3 miles of picking speed," Castellane said.

The island would be shaped like a horseshoe and planted with willows and native grasses. The center would likely remain marshy, as a sort of wetland, providing habitat for shorebirds and migrating waterfowl. The corps would dig an 8-foot-deep trench in the river bottom just downstream of the island to provide an overwintering and spawning spot for fish. The island's shoreline could help native and endangered mussel populations get a foothold to start rebounding in the area.

"We'd like to design the beach for a variety of shorebirds, then put in grasses and a wetland habitat where we're hoping we'll get different species of turtles nesting," Castellane said.

The project is expected to cost $3 million to $6 million. That's in the same range as the cost to reinforce the embankment by just adding rock and sand, Castellane said.

While the lock and dam isn't in danger of failing anytime soon, its embankment is eroding and will need work to ensure it lasts.

"So the question is, do we waste millions to throw more rock on it or do we try to find something that is a little more beneficial?" he said.

The corps will accept public comment on the project over the next several weeks. Funding would ultimately be decided by Congress. If approved, work could begin as soon as next year and would take about two years to complete.

The corps has been looking for ways in recent years to use the sand and muck it dredges out of its navigation channels. In Duluth harbor, the corps will use dredged material to double the size of an island that's become home to one of the last nesting sites of common terns in Minnesota. It's also using those dredgings to reinforce the beaches along Minnesota Point, a project that has reignited a 40-year-old legal fight over releasing dredge material into Lake Superior.

There's been a push in recent years to restore islands or build new ones along the Mississippi River to re-establish lost mussel colonies and habitat for fish to spawn.

The Minneapolis Park Board has reconstructed islands and is planning to restore the shoreline above the now-closed lock and dam at Upper St. Anthony falls in the hopes of bringing back a more natural fishery.

Just upstream from the Hastings lock and dam, Lake Rebecca is a popular fishing spot. The island, Castellane said, may help extend some of that good fishing downstream.

"I go to Lake Rebecca all the time with my kids and I think a lot of people who do are going to love to canoe and kayak around the island," he said.

Greg Stanley • 612-673-4882