Northwater was retained to complete all technical aspects of the Waverly Lake Total Maximum Daily Load (TMDL) and Watershed Implementation Plan, funded by the Illinois EPA and City of Waverly. Waverly Lake is located in Morgan County, Illinois, and is a public water supply for the city and surrounding communities. The 107-acre reservoir is a local recreation resource and is impaired for total phosphorus and siltation.
Technical roles included TMDL modeling, a detailed watershed characterization and advanced GIS spatial analysis and mapping, identifying site-specific watershed Best Management Practices, landowner outreach, public participation, and a custom map-based watershed pollution load model (SWAMM).
The model was built to quantify and locate sediment, nitrogen, and phosphorus loading to the lake. It included development of a GIS landuse layer, soils, and precipitation, and was used to calibrate a BATHTUB model used in generating the phosphorus TMDL. Modeling resulted in spatially explicit loading by land/parcel unit and was used to quantify load reductions from watershed treatment practices and identify “critical areas.”
Additional activities included: a direct assessment and mapping of streambank and lake bank erosion, a gully erosion inventory, mapping of field-specific tillage practices, a riparian buffer quality analysis, landowner coordination, and the submission of a $550,000 grant application to fund plan recommendations. The TMDL and Watershed Plan was completed one year ahead of schedule.
The grant was awarded in 2017 and work is scheduled to be completed in 2019. Northwater was hired to manage all aspects of project including landowner coordination, reporting, permitting, and the survey and design of over 100 individual practices focused on reducing phosphorus and sediment loading within and to the lake.
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