A leaky rock dam behind nearly 50 years of headaches will finally be replaced with a more fish-friendly option.
Construction is expected to begin next week on the dam regulating water flow between the Pine River and Big Pine Lake in Crosslake, backed in part by a $1.2 million grant from the state’s Outdoor Heritage Fund. Built in 1970 and owned by the county, the rock dam set for replacement has required a large number of repairs over the years and is in fragile condition, nearing the end of its useful life. Work is scheduled for January due to the low flow of the river this time of year, County Engineer Tim Bray said.
In requesting funding from the Lessard-Sams Outdoor Heritage Council, which makes funding recommendations to the state Legislature to distribute dollars from the Legacy Amendment-funded Outdoor Heritage Fund, the Crow Wing Soil and Water Conservation District noted its concern the seeping rock dam could fail.
“The effects would be devastating, draining over 400 acres of Big Pine Lake and impacting acres of high quality vegetation and aquatic habitat. The low water levels would also affect fisheries, loon nesting, and recreational use of boats, canoes and kayaks,” Beth Hippert of the SWCD wrote.
The dam is a threat to the health and diversity of aquatic organisms and migratory fish in the river, lake and upstream waters, according to the SWCD. Among the fish species affected by the dam are three considered at risk by the Minnesota Department of Natural Resources: the greater redhorse, pugnose shiner and least darter.
The greater redhorse is a sucker — sometimes mistaken for a carp — that can grow up to 2 feet and features a red tail and rows of dark spots. Pugnose shiners are small minnows with large eyes and an almost vertical mouth, giving it its namesake pugnose appearance. The least darter rarely grows more than 1.2 inches in length and is the smallest fish in Minnesota, according to the University of Minnesota, and has a small black band on its head and mottled fins. A survey of the area showed none of these species were present upstream of the dam, while they were spotted downstream.
“Reconnecting this downstream stretch with upstream habitat in Big Pine Lake will open up spawning habitat for this species, as well as associated aquatic organisms and fish dependent on diverse aquatic plant communities,” the SWCD stated in its grant application.
Replacing the aging rock dam will be a series of five rock weirs, coaxing the water to flow on a gradual downward slope toward the narrowing banks of the tributary and creating deep pools. The weir arrangement is called an arch riffle structure and uses various sizes of boulders, fabric and sediment to minimize water seepage.
“This project will permanently open a 20-mile aquatic corridor, plus tributaries in the watershed between the confluence of the Mississippi and the Crosslake Dam,” the grant application stated. “More than a mile of public land that flanks the project area will be leveraged to enhance benefits, and it is also linked to 4,000 acres of woodlands, open prairies, and wetland complexes.”
On Tuesday, Dec. 31, Bray asked the county board to approve a lease agreement with the DNR for state-owned land, allowing access for construction equipment and any future maintenance. The Crow Wing County Highway Department will maintain the new dam once it’s complete. The board approved the lease, which amounted to less than $2,000 for 10 years. A groundbreaking ceremony is scheduled for Friday, Jan. 3.
This project will be monitored by Crow Wing SWCD to ensure it is functioning as designed and is stable and effective. Significant long-term maintenance costs are not expected because it follows natural channel design principles, which create self-sustaining habitat conditions.
Any maintenance costs will be covered by the Big Pine Lake Subordinate Services District fund administered by the county. Nearly 100 riparian landowners on Big Pine Lake are assessed $200 annually per property.