Thorpe Sediment Basin Project

thorpe6-11-15 1Cardno JFNew was contracted by the Wawasee Area Conservancy Foundation (WACF) in July 2012 regarding a recently purchased 4.51 acre parcel in Section 27, Township 34 North, Range 7 East, Kosciusko County, Indiana. The parcel is known as the Thorpe property with access from County Road 1000 North, approximately midway between State Road 13 and County Road 800 East. WACF purchased the parcel to develop a Best Management Practice for reducing sediment and controlling stormwater in the Martin drainage. The entire Martin Drain Watershed is approximately 240 acres, while the drainage area that includes the Thorpe property and above is approximately 120 acres. Approximately 80 acres of the drainage above the Thorpe parcel is row crop agriculture. The intermittently flowing Martin Drain empties into a thorpe11-11-14 1manmade channel off Lake Wawasee in Vawter Park Subdivision. That lake channel receives sediment laden water from Martin Drain following any rainfall that generates a discharge.

While there is no defined stream channel above or within the Thorpe parcel, there is an 18-inch diameter clay tile entering the property from the southwest and discharging onto the neighboring property along the north property line. This tile line followed the lowest elevations of the property and the resulting discharge was at a wetland that is in part on WACF property. The wetland is primarily silver maples; however, the portion on the Thorpe parcel is primarily reed canary grass and had been significantly impacted from past erosion of the adjacent slope. A high ridge that was previously cultivated makes up the majority of the parcel. This ridge was dominated by annuals, primarily foxtail, and is bordered to the east by wooded residential lots and on the south and west by a wooded fence row and a large agricultural field. The agricultural field is under a conservation tillage program; however, the field is still occasionally tilled allowing surface erosion of sediment.

Project Details…

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Thorpe Basin Drainage Upgrade

While the Thorpe Basin has done a good job of filtering sediment that would previously have run into Lake Wawasee, it was noted in 2016 that during heavy rain events, there was considerable flooding in the area surrounding the basin. A study funded by WACF determined that the old, existing drainage in the area was inadequate and a new system would be required. The new system will require a substantial investment but was deemed necessary by the WACF board of directors. Construction of the new system will take place in early 2017.

Details of the new system