Listing Guideline

When there are persistent water quality problems (e.g. dissolved oxygen depletion of bottom waters, nuisance algal blooms or accumulation, decreased water clarity, etc.) attributed to cultural eutrophication.

Delisting Guideline

When there are no persistent water quality problems (e.g. dissolved oxygen depletion of bottom waters, nuisance algal blooms or accumulation decreased water clarity, etc.) attributed to cultural eutrophication.

Delisting Targets

  • Total phosphorus (TP) concentrations within the AOC rivers, harbors, and nearshore waters meet the criteria recommended for the State of Wisconsin, as established by WDNR.
  • When the results from the total maximum daily load study for phosphorus, total suspended solids, and bacteria are completed for the Menomonee, Kinnickinnic, and Milwaukee Rivers.
  • Measures to meet the Total Maximum Daily Loading Implementation Plan are being completed.
  • No water bodies within the AOC are included on the list of impaired waters due to nutrients or excessive algal growths in the most recent WI Impaired Waters list.
  • Chlorophyll-a concentrations within the AOC lake and impoundment areas do not exceed 4.0 µg/L.
  • There are no beach closures in the AOC due to excessive nuisance algae growth.

Sources of Pollution or Problem

  • Contaminated sediments; spills of chemicals within the watershed; atmospheric deposition
  • Sediment, nutrients, and bacteria as a result of nonpoint, or diffuse, sources of pollution; urban stormwater runoff; sewer overflows; noncontact cooling water
  • Dams, drop structures, concrete-lined channels, and poorly-sized culverts and stream crossings; shoreline alteration, such as sheet piling, that doesn’t provide high-quality habitat
  • Discharges of water with elevated temperatures

Remediation Actions

MMSD received GLRI funding to complete third-party TMDL analyses on the Kinnickinnic, Menomonee, and Milwaukee Rivers and the Milwaukee Estuary. While the project was scheduled to be completed by the end of 2013, delays have pushed back the completion date to 2016, with implementation to follow.

Moving Forward

The results from the TMDL study should be helpful in determining what progress can be made with regard to the issue of phosphorus loading in the estuary, and improving water quality. Once the TMDL has been completed and the implementation plan has been prepared, we will have a better idea if the AOC program will need to do anything further in order to remove this BUI. Support for TMDL implementation will be important, but it is not clear at this time what AOC management actions would be needed.

Nonpoint source pollution is a challenge to making progress on this impairment. Therefore, addressing nonpoint source pollution throughout the watersheds is a priority issue for continuing to make progress in the Estuary. Green infrastructure projects and implementation of other stormwater best management practice projects should be a priority to address this issue.

A complete list of management actions that are necessary to move towards removing this impairment has not been defined. Decisions on management actions can begin when the results of the TMDLs are available.


The physical conditions within the estuary itself have not changed so despite the substantially decreased contributions of organic material from sewer overflows, meeting the designated fish and aquatic uses may still be difficult. Another challenge for addressing this impairment will be the contribution of orthophosphate to total phosphorus levels in waterbodies in the AOC. Some municipal water supplies in the AOC add orthophosphate as an anticorrosive agent. Under Wisconsin state statute and administrative code (Section 283.35, Wis. Stats. and Section NR 205.08, Wis. Adm. Code), this treated water is used in some non-process waters, (e.g., cooling systems) and directly discharged without having the orthophosphate removed. The orthophosphate increases the total phosphorus concentrations in waterbodies and can contribute to further algal growth.

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Photo courtesy of Circle of Blue