Thief River Falls Oxbow Restoration and Stormwater Treatment Project
Project Summary
The Thief River Falls Water Quality study examined stormwater runoff throughout the city and identified priority projects for treating stormwater runoff. The Thief River Falls Oxbow Restoration and Stormwater Treatment project will complete one of the priority projects that was identified by that study to protect water quality. The project will restore 3 acres of an oxbow wetland by removing accumulated sediment to restore the wetland habitat, filtration, and retention qualities. The project will also incorporate measures to trap pollutants and trash from future stormwater runoff upstream of the wetland. These measures will reduce concentrations of total suspended solids (TSS) and other pollutants in stormwater runoff that contribute to downstream impairments of the Red Lake River within a priority watershed of the Red Lake River One Watershed One Plan.
Stormwater treatment within the existing wetland will be increased by providing detention via a controlled outlet structure and reconstruction of portions of the wetland. The project will restore the oxbow wetland’s capability to reduce pollution by slowing the rate of run-off(storage) and helping keep run-off clean (filtration). Ponding areas and native wetland vegetation will provide additional treatment. In addition to restoring the functionality of the oxbow wetland by removing approximately 10,000 cubic yards of sediment, this project will construct a pond and install hydrodynamic separator structures to minimize pollutant contributions from a snow disposal site on the east side of Pennington Avenue South. A settling pond will be constructed around the riser pipe that drains the snow dumping area on the eastside of Pennington Avenue. This project will further reduce the pollutants entering the wetland by installing multiple hydrodynamic separator structures to remove trash and sediment. A rock structure will be constructed at the west end of the oxbow wetland to stabilize the outlet, ensure that the pond will continue to hold water, and oxygenate water as it flows out of the pond.
Multiple sources of funding made this project possible. The city of Thief River Falls invested in the engineering work needed to develop a concept for the project. The Red Lake Watershed District successfully applied for funding from the Red River Watershed Management Board ($250,000 total) and a Minnesota Board of Water and Soil Resources Clean Water Fund Grant ($250,000). Financial contributions from the City of Thief River Falls and the Red Lake Watershed District will cover the remaining portion of the project costs.
Construction (excavation of sediment from the oxbow wetland) began in mid-August, 2021.
Project Progress
Much progress has been made on excavation of the sediment that had accumulated in the oxbow wetland. Work has begun on the installation of underground structures that will remove a portion of sediment and trash from stormwater runoff, upstream of the wetland.