July 17, 2008
Lower Minnesota Poses Challenge for Storage of Dredge Material
By Tim Krohn, The Free Press, Mankato, Minn.
Jul. 17--CHASKA -- The final 15 miles of the Minnesota River are dramatically different than the other 300 miles. The lower Minnesota winds through 15 communities in four metropolitan counties, running next to the Twin Cities International Airport and Mall of America and filled with barges carrying Midwest grain to world markets.
The area is under the jurisdiction of the Lower Minnesota River Watershed District, which works closely with the U. S. Army Corps of Engineers to keep the river navigable for commerce.
" The barges have a 9- foot draft, so we have to maintain a 9- foot channel," said Terry Scwalbe, district administrator of the watershed.
The channel was built from 1966 to 1968 under authorization by Congress.
With a river that carries a lot of sediment, there is usually dredging going on somewhere on the channel.
Finding a place to put more than 10,000 yards of dredge material each year had become a major problem for the Corps and watershed district since 1970.
The U. S. Fish and Wildlife Service and Department of Natural Resources hold most of the riverside land on the lower Minnesota as part of a major wildlife refuge, leaving few places for putting the dredge material.
" Over the years we'd get easements to some lands, but with changes in the Wetland Act, we couldn't use them," Scwalbe said.
The agency just recently bought an 18- acre site from Cargill to store the dredge material. But the nutrientheavy sediment won't just pile up.
" We plant to market it and recycle it. It'll probably be mixed with mulch for topsoil. It's very rich," he said.
While the district deals with the commercial aspect of the river, the agency's focus has continued to shift more toward environmental protection and restoration along the lower Minnesota.
" We have a lot of unique areas, the Savage Fen, Seminary Fen, Camp Coldwater Spring and a boiling springs," Schwalbe said.
The boiling springs is the only naturally producing trout stream in the Twin Cities metropolitan area. Water boils up out of the ground about 2 feet near Savage, creating a pristine stream that goes to the Minnesota.
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