CD62 Multipurpose Drainage BMPs Put to Work

Faribault County Ditch 62 is a 658 acre, all tile, public drainage system which outlets to an unnamed tributary of the Blue Earth River. The landowner at the outlet wanted to do something to treat the water from the public drainage system. This included installing a water quality unit, three large denitrifying bioreactors, and 5 alternative (conservation based) surface inlets within the watershed.  Surface inlets are vertical tile brought up to the surface to drain standing water in depressions in the landscape. Alternative surface inlets are designed to drain the standing water in a way that reduces debris and sediment to the tile line. The water quality unit is essentially an underground storage tank with weir plates to slow flow and allow pollutants, suspended solids, and debris to settle out.

The work of the woodchip bioreactors takes place underground, in the case of CD62 below a grass swale so no land was taken out of production. Woodchips were placed in three underground trenches, and tile water was diverted through the bioreactors to remove nitrates from the subsurface drainage water. Water exiting the bioreactors was routed back into the underground tile with lower nitrogen concentration. The bioreactors and water quality unit are completely off line from the drainage system main and are considered part of the legal drainage system.

Bioreactors serve as part of a ‘treatment train’ approach to improve water quality and can be paired with other conservation practices, including alternative inlets to reduce the amount of pollutants reaching downstream surface waters. This project is the first application of a water quality unit in an agricultural setting and the largest treated watershed by bioreactors known in MN.

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 Faribault County Ag Center • 415 S Grove Street, Suite 8 Blue Earth MN 56013 • Phone 507-526-2388 • Fax 507-526-2508 • M-F 7:00AM-4:30PM Site Designed by BEVCOMM