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In 2008, Minnesota voters approved the Clean Water, Land and Legacy Amendment which, among other funds, established the Clean Water Fund. The Clean Water Fund has greatly improved water quality monitoring in Minnesota and, as a result, enabled stronger and more nuanced water protections, including aquatic life use designations.

One of the most important beneficial uses protected by Minnesota rule and the Clean Water Act is aquatic life (Class 2 – Aquatic life and recreation).

  1. It protects ecosystems, habitats, and aquatic biota including fish, insects, mollusks, crustaceans, plans, microscopic organisms, and all other aquatic-dependent organisms.
  2. It protects recreational uses such as swimming, fishing, hunting, and boating.
  3. It is assigned to nearly every waterbody in the state.

Use designations are routinely reviewed to ensure that beneficial uses assigned to streams, lakes and wetlands are protective and attainable as defined by the Clean Water Act (CWA) and Minnesota Rule (see Past and ongoing revisions to aquatic life use rules and designations). The process for reviewing use designations is described in more detail in the technical guidance:

The designated use for each water body needs to be appropriate because the designated use affects many water quality protection and restoration efforts including assessments, stressor identification, National Pollutant Discharge Elimination System (NPDES) permitting, and Total Maximum Daily Loads (TMDLs). The specific use designations assigned to Minnesota’s waters are listed under the section.

To account for natural differences between aquatic habitats or differences in the highest or best attainable conditions, Class 2 is divided into subclasses and then into aquatic life use tiers. The hierarchical nature of this beneficial use framework permits the assignment of appropriate and attainable goals for these waterbodies.

Class 2 subclasses

Class 2 is divided into 4 subclasses:

  • Class 2A: Cold water habitat – lakes and streams
  • Class 2B: Warm water habitat – lakes and streams
  • Class 2Bd: Warm water habitat also protected as a source for drinking water – lakes and streams
  • Class 2D: Wetlands

Different standards may apply to aquatic habitat types because background levels of pollutants may not be similar or they may not support the same beneficial uses. For example, a lake may protect swimming as a beneficial use, but this beneficial use may not be protected in a wetland. Furthermore, within the subclasses some standards may be further refined to account for natural differences between habitats and regions. For example, different eutrophication standards may be applied to lakes and streams due to natural differences in background conditions and how additions of nutrients affect these waterbody types.

Tiered aquatic life uses

Aquatic life beneficial uses for streams in Class 2A, 2B, and 2Bd are further refined to account for the highest biological goal that can be attained in a stream. This is called the Tiered aquatic life uses framework (TALU) and it represents a significant revision to the aquatic life use classification in the state's water quality standards. It builds upon existing water quality standards to improve how water quality in streams and rivers is monitored and managed. The TALU framework relies on a combination of biological, physical, and chemical monitoring to measure the attainment of aquatic life goals directly. The TALU framework also produces a systematic process with a monitoring and assessment program that collects the right kinds of data which can be used at the same scale that management is being applied. As a result, monitoring and assessment work in parallel with water quality standards to develop effective standards that result in the protection of designated uses.

The TALU framework moved Minnesota's aquatic life standards from a “one-size-fits-all” approach to one that protects appropriately classified waters based on their biological potential. This means that high quality or Exceptional Use waters are given additional protection to ensure that the condition of these habitats are maintained. The majority of streams and rivers continue to be protected as General Use or good quality waters. Some waters that are impacted by legacy or historical impacts (for example ditches) may be eligible for a lower goal if it is demonstrated that the biology cannot attain at least the General Use. For these streams, a Use Attainability Analysis (UAA) needs to be performed to determine if habitat is limiting the biology and what is the cause of the poor habitat. Biological communities that are limited by habitat that are a result of legal activities (for example ditch maintenance) could be redesignated Modified Use. The scientific underpinnings of the TALU framework are described in detail in the following documents:

Past and ongoing revisions to aquatic life use rules and designations

2018: Minnesota adopted changes to its water quality standards (Minn. Rule Chapters 7050 and 7052) that establish a tiered aquatic life uses (TALU) framework for rivers and streams. These rule amendments affect Class 2 (Aquatic Life) standards. The EPA approved the TALU framework rule in 2018.

2020: The Minnesota Pollution Control Agency (MPCA) adopted amendments to rules governing water quality standards: Class 2 and Class 7 use designations, Minnesota Rules chapter 7050. The rule amendments are effective as of June 8, 2020.

Beneficial use designations for Minnesota waters

See the Incorporations by reference web page for a list of beneficial use designations for stream reaches.