Aboard a Mississippi River paddleboat, federal officials talked about dredging a new navigation channel in Spring Lake.
The Mississippi River's underwater channel through Spring Lake north of Hastings could be re-routed at a cost of millions, potentially making navigation easier for barges and creating a new island that could improve conditions for wildlife and anglers.
The 9-foot-deep, 200-foot-wide channel makes a troublesome turn of nearly 90 degrees in the lake between Cottage Grove and Nininger Township. The new channel would eliminate most of the sharp turn that is often clogged with enough silt to cause large, towboat-propelled barge convoys to run aground.
And the sand and muck dredged from the riverbed could be put to good use, said Laura Jester, a Dakota County soil and water district manager and coordinator of the Mississippi Makeover project.
"Building an island in Pool 2 [in Spring Lake] is our No. 1 priority," Jester said. "An island would go a long way to reducing the wind, which hurts river quality and vegetation."
The wide-open expanse on Spring Lake increases wind speed, which creates more wave action. That stirs up sediment, which refills the channel. The veil of sediment also reduces water quality which, in turn, impairs habitat for aquatic plants, fish and wading birds, and hinders recreational use, officials said.
The meandering navigation channel is maintained at 9 feet deep by the U.S. Army Corps of Engineers. The corps has been analyzing the cost-effectiveness of two channel improvement options and meeting with local groups for input for more than a year. The corps' interest is partly prompted by the almost doubling of dredged material removed annually since 2006 from the 3-mile big bend in Spring Lake, said Paul Machajewski, channel maintenance coordinator for the corps' St. Paul district.
He said the project would cost more than $5 million. Machajewski spoke at a floating workshop for about 160 city, county and watershed officials and residents aboard the two-deck Anson Northrup paddleboat this month.
He said a less expensive option is to improve and add riprap and wing dams -- the wood-and-rock structures built out from banks to direct river flow into the channel. The corps built about 300 wing dams between Hastings and St. Paul in 1925, before the Hastings lock and dam was built in 1930. Some of those wing dams have disappeared.
St. Paul District Engineer Col. Michael Price will decide this summer which option to pursue. Then the corps will develop design plans, do an environmental impact study, and seek state permits and local endorsements by year's end, Machajewski said. He said the corps has money in its 2013 budget for dredging a new channel, which would take about three months next summer.
A straighter channel would reduce recurrent dredging costs by about a third, he said.
An improved channel is sorely needed by the barge towing industry and its customers, said Greg Genz, vice president of the Upper Mississippi Waterway Association. He said the normal tow load is 15 barges, but that is only possible in Spring Lake for a few weeks after dredging. During one month last year only a six-barge tow could get through the right-angle channel off the Nininger Township peninsula, he said.
Although many local groups like the island idea, and hope to obtain state Legacy Amendment or lottery-funded water quality grants, the corps has no money allotted to create an island, Machajewski said.
The corps study assumes the dredged material would be deposited on nearby Grey Cloud Island, as in the past. Officials said that dredge-based islands built on the river farther south have significantly reduced water turbidity.
However, a new Spring Lake island's impact on the upstream floodplain may be a bigger obstacle than cost, Machajewski said.
"I realize that is a hurdle," Jester said. "That is something we have to work through in the engineering study."
Jim Adams • 952-746-3283