A $1.7 million grant to the Nicollet County Soil and Water Conservation District early this year is helping boost some big projects in the Seven Mile Creek Watershed.

A field day last month showed off some of the work that has been happening in the watershed, including tiling projects and the installation of a woodchip bioreactor.

Minnesota Rep. Clark Johnson (DFL-North Mankato) spoke briefly during the field day, praising the work that’s happening in the Seven Mile Creek Watershed.

“Here, producers are taking the lead on water quality,” Johnson said.

Seven Mile Creek runs from west to east south of St. Peter into the Minnesota River. Karen Galles is Seven Mile Creek Watershed coordinator. While much of her work to this point has been on stabilizing ravines in the area, she has enjoyed the opportunity the grant funding has given to look at bigger projects.

Grant-funded projects in the watershed are just getting started. Funding from the grant runs through 2019.

“If you’ve got an idea, I bet I can find a way to make it work with our grant,” Galles told attendees at the field day, while also reminding producers of the importance of projects that aren’t grant cycle-reliant.

Farmer Chuck Peters shared his experience of adding four control structures to his tiling system. The structures can help keep some water on the land and reduce the amount of nitrates that leave the land as well. Peters can then control the subsurface water level.

“It gives us an opportunity to manage our situation in August when it’s dry,” Peters said.

Controlled drainage like Peters’s is a win-win situation, Galles said.

“It gets at a root cause of water quality issues,” Galles said.

Bioreactors

Mark Dittrich is the senior planner for conservation drainage with the Minnesota Department of Agriculture. Bioreactors are one of his areas of expertise.

A woodchip bioreactor is basically a trench with a small grade decline along its bottom that is filled with hardwood wood chips, has a control structure at each end and is covered over with soil. Tile lines lead to and from the bioreactor. As it works, naturally-occurring bacteria in the bioreactor eat the available oxygen and then the available nitrogen and even phosphorous, cleaning the water as they go. They can also help reduce some chemicals in the water, such as atrizine, Dittrich said.

“(Woodchip bioreactors) use plumbing and biology to convert nitrogen to gas,” Dittrich explained. “One of the biggest challenges is getting over the design hump.”

Paul Sweeney, director of conservation planning with Ecosystem Services Exchange, said bioreactors can be added into tile retrofits, but are easiest to install into new tiling systems. There is also a fair amount of financial assistance available for those installing reactors.

Bioreactors can reduce the volume of nutrients in tile water by 15 to 60 percent, though it can only manage a portion of the total tile flow, Dittrich said.

The bioreactor being installed during the field day was along a shared tile line leading to a ditch. It was still in the relatively early stages, with control structures being installed at the ends of the pit. Plastic had been laid over the pit to help prevent groundwater from seeping into the reactor from below and a swale will be constructed to route most groundwater from above around the area where the bioreactor is.

The University of Minnesota helped design the bioreactor. When finished, the reactor will be 115 feet long, 25 feet wide and 5 feet deep. It’s graded so there’s a half-foot fall from the inlet to the outlet. Two to three feet of soil will go on top of the finished bioreactor. At peak flow, it will treat 15 to 25 percent of the water going through the tile line. The bioreactor will be able to retain water for five to six hours and reduce 60 to 85 percent of the nitrogen in the water that will flow through it. The cost for constructing the bioreactor is $49,700.

Bioreactor install

Bioreactor install

Excerpt of article by Lisa Young for AgriNews, Oct 9, 2015.

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