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In recent years, the river banks at a bend in the Crow River on the east side of St. Michael have slowly been eroding, sending tons of soil down the river and on into the Mississippi -- and the erosion was worsening, threatening to wipe out a city stormwater pond. The traditional approach to the problem would entail armoring the riverbank with massive amounts of large rocks or rip-rap, an approach that’s biologically sterile and would cost millions of dollars – a high price tag for cash-strapped local units of government.
That’s when staff with the Crow River Organization of Water (CROW) contacted Nick Proulx, a DNR clean water specialist. Proulx began looking into a much cheaper method of controlling stream bank erosion that had been used successfully on the Le Sueur River in southern Minnesota and elsewhere.
Toe-wood stream bank stabilization, as it’s called, involves burying logs, some with root wads still attached, along the outside bend of the river, some poking up from the stream channel. Then they’re covered with soil and plantings of woody vegetation such as alder and willow, as well as grasses and sedges. The approach tries to work with a river’s flow and forces, rather than locking it in place, Proulx explained. It results in a more natural channel and creates floodplain, a stabilized stream bank, less erosion and sediment in the water, and better habitat for aquatic organisms.
“It’s a fairly new approach that’s gaining steam,” Proulx said. “We’re trying to demonstrate that this is a valid alternative to rip-rap, a valid approach to infrastructure protection at a much cheaper cost.”
And when Proulx said the toe-wood stabilization is “much cheaper,” that may be an understatement. A similar stream bank stabilization project using rip-rap in Delano cost $2.4 million. Price tag for the St. Michael toe-wood stabilization work: $183,000 – less than one-tenth of the traditional approach. About $64,000 of that came from a Clean Water Legacy grant awarded to the Wright County Soil and Water Conservation District; the grant was funded by a sales tax increase approved by voters five years ago last November. The rest was paid for by CROW and the city of St. Michael. Proulx, who helped design the project and oversaw its construction, also is paid with Clean Water Legacy funds.
“Imagine 30 dump trucks backing up to the Crow River and dumping a load of dirt into it each year,” Proulx said. “That’s how much erosion was going on before this project. That’s a pretty significant reduction in pollution, and a big improvement in water quality.”
Find more information about the DNR’s Legacy Amendment funded projects at www.mndnr.gov/legacy.
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