The lock and dam on the Mississippi River near Red Wing, Minn., the site of more than 100 barge accidents because of the hazardous current, will undergo $70 million in safety improvements over the next two years under the nation's economic stimulus program, according to the Army Corps of Engineers.

It is one of the Corps' largest projects under the program, although a long-standing conflict with the Wisconsin Department of Natural Resources (DNR) over the lack of a fish passage threatens to block some of the work.

Critics led by the Wisconsin DNR also object to the Corps' plans to cut down trees used by perching bald eagles and to embed concrete blocks along vast stretches of shore and bottom land on the Wisconsin side of the river.

The Corps says the lock has the second-highest risk of failure of any U.S. navigation project, and part of the $70 million in renovations aims to reduce that risk.

The problem is that the lock was built on a marshy bend in the river. The current pushes southbound barges away from the lock on the Minnesota bank, and toward the concrete dam.

In 1993, a barge carrying soybeans crashed into the dam and sank, forcing a shutdown in river traffic. In 2005, two out-of-control barges went through a dam gate.

Corps engineers fear worse -- a barge crash that could block the dam gates and force water toward the Wisconsin embankment, eroding a new channel and draining the pool. That would halt shipping, damage wetlands and expose water intakes for two upstream power plants, forcing them to shut down, according to a 2006 Corps study.

To get the project underway quickly -- and create about 500 jobs -- construction will begin before the design is completed, a process known as design-build, Corps officials said. This method was successfully used to replace the collapsed Interstate 35W bridge, but this is the first time the Corps' St. Paul district has tried it.

In the renovation, the Corps would extend a concrete wall that runs almost in the middle of the river so barges would have a safer approach to the lock. Much of the rest of the work is planned on the Wisconsin side, shoring up dikes, weirs, lake outlets and embankments.

The dikes and weir are unusual features of this lock because they were designed to overflow into two floodplain lakes that are part of a 1,500-acre private preserve.

Almost all of the work would be done in the winter, to avoid the shipping season, said Terry Williams, a Corps project manager. Firms that wish to bid on the design-build project must submit their qualifications by June 30, and those chosen to compete must submit proposals by Aug. 31, she said. The goal is to complete all work by September 2011.

Oops, no fish passage

Upper Mississippi River locks built in the 1930s don't have fish passages, which allow sturgeon, paddlefish and other species to easily get by the dams. When the Corps announced $1.8 billion in projects under the Recovery and Reinvestment Act last month, it said the Lock & Dam No. 3 renovation would include a fish passage.

The announcement was a mistake, the Corps says.

"We had recommended including a fishway feature in the stimulus bill, but somewhere in Washington it was removed," said Daniel Wilcox, a Corps biologist in St. Paul who has studied the project's environmental effects.

The Corps, which once opposed fishways, says it would build one on Lock & Dam No. 3 if it had another $10 million or more.

Wisconsin's DNR says now is the time to add a fish passage, and it has threatened to deny two key permits to the Corps if the project doesn't include one. The agency also objects to other changes proposed below the dam on the Wisconsin shore.

"It is going to look dramatically different than it does now," said David Pericak, the DNR's aquatic habitat coordinator for that region, said of the area downstream of the lock. "It is going to look more like a manicured urban setting with low, grassy vegetation."

Large cottonwoods and maples will be cut down, and 19 acres of wetlands will be lost, he said. Concrete blocks, linked by cables, will be embedded in the ground to strengthen banks and new spillways. One such structure would be more than one-third of a mile long.

DNR biologists also are concerned about mussel beds and the walleye fishery just below the dam.

"If the fishermen knew what was going to change, there would be public outcry," Pericak said.

DNR and Corps officials will meet this week to discuss the lingering issues.

Wilcox, the Corps fisheries biologist, said the agency spent years reevaluating the project after Wisconsin raised concerns in the 1990s.

He said a lot has been done to reduce and mitigate environmental damage, including an agreement to buy 300 acres of river bottomland nearby and restore it to floodplain forest. Some land already has been purchased on the Rush River in Pierce County, Wisconsin.

"We went a long way to try to accommodate their concerns and minimize the construction footprint," Wilcox added.

David Shaffer • 612-673-7090