Natural Resources Research Institute Technical Report

Executive Summary to the Beneficial Use Impairment Actions Associated with Investigations of Paleolimnology and Historic and Current Water Quality Condition in the St. Louis River Area of ConcernThe St. Louis River Watershed which drains to the St. Louis River and its associated estuary near Lake Superior has more than 150 years of human development history since Euro‐Americans first settled there, resulting in critical water quality impacts. In 1987, the U.S. Environmental Protection Agency designated the St. Louis River as an Area of Concern primarily due to that history which entailed inappropriate discharge of untreated wastewater and debris from poor industrial and community practices. The organic matter loading from inadequate treatment of sewage and paper mill products along with the dumping of woody debris from sawmills contributed to low oxygen levels in the river. The result included devastating impacts to the entire food web from the bacteria to vegetation to invertebrates to fish. Concurrently, poorly managed stormwater runoff from this post‐logged, barren landscape contributed excessive loading of suspended sediments resulting in increased turbidity and nutrient concentrations (e.g., phosphorus, nitrogen) to the river. Since then, government and private entities have taken action to restore the water quality in the St. Louis River Estuary, and to eventually remove the eight remaining SLRAOC BUIs. This summary focuses on the research documenting water quality changes over time associated with the excessive loading of sediment and nutrients BUI.Center for Water and the Environment, Natural Resources Research Institute, University of Minnesota Duluth, 5013 Miller Trunk Hwy, Duluth, MN 55731. This report was produced by the Natural Resources Research Institute under contract to the Minnesota Pollution Control Agency and funded by the Minnesota Clean Water, Land and Legacy Amendment Clean Water Fund. The project was partially funded by the Minnesota Sea Grant College Program, NOAA, Department of Commerce under grant number NA14OAR4170080