One rain garden and two stormwater pond renovations were completed in November to treat stormwater before it reaches Martin and Coon Lakes. The projects will collectively treat 39 acres of residential development that previously were draining to the lakes with little or no treatment. They will keep 2,100 pounds of sediment and 5 pounds of phosphorus from reaching the lakes each year.
These waterbodies were priorities because both lakes are surrounded by homes and heavily used for recreation. Martin Lake is nearing the criteria for being removed from the State's list of impaired waters. Coon Lake has good water quality but is under pressure.
The rain garden was constructed in cooperation with a residential landowner along Hupp Street. Their property is a key location where drainage from 8 acres converged and entered a catch basin that piped stormwater to Coon Lake. Curb cuts on each side of the catch basin now intercept that water, allowing it to soak into the ground within the rain garden. Pollutant removal is estimated to increase by 52% compared to the pre-project condition. Mulching and planting of the gardens will be delayed until spring 2021 due to cold temperatures early in fall 2020. The property owners will maintain the garden.
The stormwater pond projects are redesigns and renovations of older ponds. Both ponds are on Martin Lakeshore within township-owned property. Both basins had filled with sediment over time and were providing little water quality treatment. Now, the basins are even larger than originally constructed to maximize pollutant removal. Pollutant removal is estimated to increase by 84% and 104%, respectively, at the two ponds. Linwood Township will own and maintain the basins.
These projects are part of a State Clean Water, Land and Legacy grant to the Sunrise River Watershed Management Organization. The Anoka Conservation District is managing the projects. Additional funds remain and will be used for similar projects in 2021.
Collaborators on these projects included the ACD, SRWMO, Martin Lakers Association, Linwood Township, and the City of East Bethel.