Tons of dirt was carried into Knowlton Creek, flowing downstream until it settled in the backwaters of the St. Louis River behind Tallas Island and choked off what had been prime fish habitat.This month, crews are vacuuming up 75,000 cubic yards of that mud and restoring an open-water channel around the entire island for boaters, anglers and fish.They’re pumping the mud through a two-mile tube and spraying it out at the Stryker Bay Superfund site. They hope the muck — filled with seeds, bugs and invertebrates — will jump-start a new, healthy wetland ecosystem in what was one of Minnesota’s most polluted Superfund sites.

“It’s a win-win situation at both ends,” said Susan Johnson, project manager for the Minnesota Pollution Control Agency. “We are getting all this great media that has all the critters and seeds already in it to start a healthy wetland in the bay. ... And it’s re-opening what had been an open-water channel until it filled in with erosion.”

The muck will be sprayed about 6 inches deep across much of the Superfund area. It’s the fifth and final year of major work to dredge and cap massive contamination left by a century of industrial waste.The Tallas Island area, a bastion of wild surrounded by development, is home to herons, beaver, deer and bears. The new channel will include some deep holes for fish habitat. Old-timers report being able to boat around the island before the mouth of Knowlton Creek became choked with sediment.“They’ll be in there as soon as we take the (sediment) curtains down — both the fish and the fishermen,” joked Tom McGann, project manager for aetherdbs, the contractor heading the cleanup project.

The hydraulic pumping system, operated by Duluth-based Marine Tech, has been used in the harbor to dredge shipping channels. The tube is suspended by buoys, and booster pumps are on barges along the line.Some of the Tallas muck was dredged last winter and trucked to the Superfund site, and those areas already have turned a lush green.

So far, wildlife experts say the mix of cattails and grasses looks good and is mostly free from invasive species.“Part of the project requirements included re-seeding in all those areas,” the PCA’s Johnson said. “But it might not be needed. There apparently were a lot of seeds in that media and it’s already green.”Work nearly completeThe cost of cleaning up Stryker Bay Slips 6-7, one of the four largest Superfund projects in Minnesota history, will surpass $62 million by year’s end. Nearly 1 trillion pounds of sand have been used.

Much of the contaminated material has been dredged out of most of Stryker Bay and entombed in nearby Slip 6 under 180,000 cubic yards of sand. But on about one-third of Stryker Bay, cleanup crews tried a new process called “surcharging,” where tons of sand was hauled in to press the contamination down out of the water and into dry soil below.Much of the sand was removed from the Stryker site, with a little left behind topped with a carbon filter mat. Organic mud is being pumped on top to re-create the kind of wetland that might have been here before the St. Louis River estuary was industrialized.When the work is done later this year, the public and the few homeowners directly on Stryker Bay will regain their water access to the St. Louis River and harbor.

The residents also have new sand beaches along their waterfront and new docks, courtesy of XIK Corp., the company liable for and leading the cleanup.Ann Lammi, who lives across the street from the bay, said she looks forward to having the waterfront trail along the bay reopened.“I’ll be glad when it’s all over,” she said. “There’s been a lot of truck traffic and noise at times.”Slip 6 has been filled in and mostly sealed off from the river, entombing the contaminated sediment.Slip 7 has been partially capped, and a natural stream still flows through the site.

A man-made sand beach is being planted with dune grass in hopes of attracting rare shorebirds. Some of Slip 7 has been left deep enough for industrial barge use.Around much of the site, a buffer zone of trees, grass and shrubs will be left and hiking trails are expected to be built, though that’s not part of the cleanup.XIK Corp. will continue to pay for monitoring of the site, essentially in perpetuity, “to make sure what was done here is still intact and working,” Johnson said. Results will be reviewed every five years to see if additional work or changes are needed.Meanwhile, negotiations continue over the fish and wildlife portion of the Superfund case, with state, federal and tribal natural resource agencies haggling with XIK Corp. and others over the value of lost habitat and damages from the pollution.It’s possible that the responsible parties will have to pay fines or foot the bill for major fish and wildlife rehabilitation projects along the lower St. Louis River estuary.