St. Louis River Watershed Total Maximum Daily Load Report

The Clean Water Act, Section 303(d) requires total maximum daily loads (TMDLs) to be produced for surface waters that do not meet applicable water quality standards necessary to support their designated uses. A TMDL determines the maximum amount of a pollutant a receiving water body can assimilate while still achieving water quality standards and assigns load reductions needed to meet water quality standards. This TMDL study addresses the stream and lake impairments in the St. Louis River Watershed in northeastern Minnesota that are tributary to the St. Louis River above the Fond du Lac Dam. Below the Fond du Lac Dam are several smaller streams considered urban streams in and around the urbanized Duluth area. These urban streams are being addressed as part of a separate effort. The causes of impairment in the watershed include high levels of total suspended solids (TSS), Escherichia coli (E. coli), and nutrients, in addition to high temperature and low dissolved oxygen (DO), affecting aquatic life and aquatic recreation designated uses. Fifteen stream TMDLs and two lake TMDLs are provided: eleven E. coli TMDLs, two TSS TMDLs, one phosphorus stream TMDL, two phosphorus lake TMDLs, and one temperature stream TMDL.