Impaired Water - Nemadji River (Lower Nemadji River)
Douglas County, Wisconsin
LS01, LS02
0.00 - 38.20
Water is impaired due to one or more pollutants and associated quality impacts.
The Koppers site, which is undergoing RCRA corrective action, is a source of pollutants to the Nemadji River watershed.
This water was assessed during the 2014 listing cycle; total phosphorus and biological (macroinvertebrate or fish Index of Biotic Integrity (IBI) scores) sample data were clearly below 2014 WisCALM listing thresholds for the Fish and Aquatic Life use.

This water was assessed during the 2018 listing cycle; new total phosphorus sample data may meet 2018 WisCALM listing criteria for the Fish and Aquatic Life use; however, available biological data did not indicate impairment (i.e. no macroinvertebrate or fish Index of Biotic Integrity (IBI) scored in the "poor" condition category).
Listing Details
Sediment/Total Suspended Solids
Listed For
Fish and Aquatic Life
Degraded Habitat
Current Use
WWSF - Warmwater Sport Fishery
Listing Status
303d Listed
Attainable Use
WWSF - Warmwater Sport Fishery
Designated Use
WWSF - Warmwater Sport Fishery
303(d) ID
Listing Date
Impaired Water Notes
The Nemadji River flows through Minnesota and into Wisconsin. The Nemadji River watershed soils are composed of highly erodible sands and clays. The Nemadji River has the highest total suspended solids (TSS) concentrations of those measured in the Duluth-Superior Harbor, which is part of the St. Louis River AOC. On average, the Nemadji contributes a large load (~33,000 tons annually) to Superior Bay. Data were collected in 2007-2009 by WDNR and 8 out of 14 turbidity samples exceeded 25 NTU (nephelometric turbidity unit, which is the threshold used by the state of Minnesota for listing a water body as impaired) Further, the mean TSS concentration measured was 110 mg/L (median 15.5 mg/L).

Wisconsin currently does not have numeric water quality criteria for sediment that can be used to compare against the data described above to determine if a water body is impaired. However, excessive sediment in a can lead to degraded habitat impairments such as: a) covering benthic organisms that are important to the food chain; b) unsuitable substrate for fish spawning; and c) creating elevated oxygen demand in the sediment layer that prevents macro-invertebrates or early life states of fish from surviving. As a result, WDNR has chosen to apply what is know as the narrative standard for the protection of fish and other aquatic life found in s. NR 102.04 (Wis. Adm. Code):

NR 102.04 (a) Substances that will cause objectionable deposits on the shore or in the bed of a body of water, shall not be present in such amounts as to interfere with public rights in waters of the state.

The fishery that currently exists in the Nemadji River could be more robust and diverse with clearer water and better habitat. The state of Minnesota concurs and has already begun developing a TMDL to address turbidity. Including the Nemadji River on Wisconsin’s Impaired Waters List will allow the two states to work together to develop a comprehensive TMDL that will benefit the entire system.