Seminary Fen Ravine C-2 Restoration

Seminary Fen, a 600-acre complex in Carver County, supports one of only 500 calcareous fens in the world and is one of the highest quality calcareous fens in southern Minnesota. Given this fact, and the fact that it supports dozens of rare, threatened, and special concern plant and animal species, it has been characterized as one of the most significant natural areas in the Twin Cities Metropolitan Area and is part of the Minnesota Department of Natural Resources Scientific and Natural Areas program. The fen feeds Assumption Creek, one of the metro area's last known trout streams that supports naturally-reproducing native brook trout. Assumption Creek discharges to the nearby Minnesota River. The fen's unique hydrology, soils, plants, and habitats are highly sensitive to water quality and sedimentation stress.

The City of Chaska completed the C-1 Ravine Stabilization Project in 2016 with funding partners including the Board of Water and Soil Resources, Carver County Watershed Management Organization, Department of Natural Resources, and Lower Minnesota Watershed District (Figure 2). The C-1 Ravine project was estimated to reduce yearly sediment loads by 1,680 tons per year to Seminary Fen. The C-2 Ravine is the 2nd most severely eroded ravine along Seminary Fen, and the proposed improvements to C-2 are estimated to reduce sediment loads by 322 tons per year and phosphorus loads by 370 pounds per year. The sediment plume from C-2 is estimated to have expanded into 2.0 acres of Seminary Fen at the end of the ravine with depths between 2 feet and 5 feet.