Grade Stabilization for Reduction of Sedimentation in the Thief River
The Thief River is the source of drinking water for the City of Thief River Falls. The river's other designated uses also include recreation and aquatic life. Water quality monitoring conducted by local agencies discovered that the Thief River is not meeting state water quality standards for both turbidity (muddiness) and dissolved oxygen. Each year, approximately 12,376 tons of sediment is deposited into the Thief River Falls reservoir by the Thief River. That is the equivalent of over 1,200 dump trucks full of dirt. This excessive amount of sediment increases the potential of harmful byproducts getting into the city's drinking water, increases water treatment cost, and degrades the fish habitat.Marshall County Ditch 20 (CD20) is a drainage system that flows into the Thief River 7.5 miles northeast of Thief River Falls. The deepening of CD20 by erosion has been identified as a major contributor to the sedimentation problems in the Thief River and has exacerbated gully formation in fields along its course. Project partners will collaborate to implement grade stabilization and erosion control strategies along the lower 2.5 miles of CD20. Specifically, a series of rock riffle grade stabilization structures will be used to reduce the head cutting and sloughing along CD20 and side water inlets will be used to halt the gully erosion on adjacent field ditches. This project will help bring the Thief River closer to meeting the turbidity standard by reducing sediment on average by over 400 tons each year. Reducing sediment and nutrients will reduce the amount of water treatment that is need for the City of Thief River Falls and will also improve habitat for aquatic life within the river.
(b) $2,800,000 the first year and $3,124,000 the second year are for grants to watershed districts and watershed management organizations for: (i) structural or vegetative management practices that reduce storm water runoff from developed or disturbed lands to reduce the movement of sediment, nutrients, and pollutants or to leverage federal funds for restoration, protection, or enhancement of water quality in lakes, rivers, and streams and to protect groundwater and drinking water; and (ii) the installation of proven and effective water retention practices including, but not limited to, rain gardens and other vegetated infiltration basins and sediment control basins in order to keep water on the land. The projects must be of long-lasting public benefit, include a local match, and be consistent with TMDL implementation plans or local water management plans. Watershed district and watershed management organization staff and administration may be used for local match. Priority may be given to school projects that can be used to demonstrate water retention practices. Up to five percent may be used for administering the grants. (2011 - Runoff Reduction); (g) $2,330,000 the first year and $1,830,000 the second year are for grants to implement stream bank, stream channel, and shoreline protection, and restoration projects to protect water quality. Of this amount, $330,000 the first year and $330,000 the second year may be used for technical assistance and grants to establish a conservation drainage program in consultation with the Board of Water and Soil Resources and the Drainage Work Group that consists of pilot projects to retrofit existing drainage systems with water quality improvement practices, evaluate outcomes, and provide outreach to landowners, public drainage authorities, drainage engineers and contractors, and others. Of this amount, $500,000 the first year is for a grant to Hennepin County for riparian restoration and stream bank stabilization in the ten primary stream systems in Hennepin County in order to protect, enhance, and help restore the water quality of the streams and downstream receiving waters. The county shall work with watershed districts and water management organizations to identify and prioritize projects. To the extent possible, the county shall employ youth through the Minnesota Conservation Corps and Tree Trust to plant trees and shrubs to reduce erosion and stabilize stream banks. This appropriation must be matched by nonstate sources, including in-kind contributions (2011 - Shoreland Improvement)
This project has yielded an estimated sediment (TSS) reduction of 600 tons/yr.