Minnesota Pollution Control Agency (MPCA) is currently working to revise the Minnesota Water Quality Standards to incorporate a tiered aquatic life use framework for rivers and streams in the state. The Tiered Aquatic Life Use (TALU) framework represents a significant revision to the Water Quality Standards of the State’s aquatic life use classification.
MPCA conducted several public meetings to discuss the approach in January 2009, and is currently following up with smaller focused stakeholder groups. Rulemaking to incorporate TALU into State Water Quality Standards would not occur until 2010-2011.
The TALU approach utilizes biological assessments of water bodies to identify “stressed” aquatic communities. This assessment would be separate from, and in addition to, traditional current chemical monitoring of lakes and streams to determine if they meet State Water Quality Standards. TALU also provides a mechanism to determine impairments of “modified or limited water resources”, which may include channelized streams and agricultural ditches.
The biological monitoring program in Minnesota relies establishes a reference condition to set expectations for water bodies. This approach identifies water bodies that are the least stressed and uses them to establish the “reference condition.” This reference condition can then be used to evaluate other water bodies. If the condition of the water body is lower than that of the reference condition, it would be considered impacted or stressed.
TALU presents a few issues related to integration into existing regulatory programs and requirements, including:
- How will assessments made using TALU relate to determination of impairment, and the State list of Impaired Waters (“303d List”)?
- If listed on 303d List, how would a TMDL be implemented?
- How would permitted discharges be controlled if discharging to a “stressed” water body?
- How would it be determined that a discharge “causes or contributes to” an impairment if discharging to a “stressed” water body?
- How would TALU be used for “development and modification of water quality standards to produce improved standards”?
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