Proposed water quality standards work plan for 2021-2023

The MPCA has reviewed the need for water quality standard (WQS) additions and revisions. This includes reviewing the priorities laid out in the 2017 triennial standards review, the work completed since that time, program needs, and new information on the impacts of pollutants, such as provided through the monitoring of Minnesota’s surface waters by MPCA, MDA, MDH and others, and the national ambient water quality criteria (AWQC) developed by EPA. As a result of this evaluation and a review of resources for developing and implementing WQS, the MPCA has developed a list of projects that are important to move forward over the next three to five years. The list includes those projects that are currently in the rulemaking process and are a priority to complete, and other projects that are not yet ready to proceed into rulemaking but are a priority to continue moving forward.

An overview of the proposed work plan is provided below, followed by a more detailed description of each project and its expected timeline towards rulemaking.

Proposed water quality standards work plan for 2021 to 2023 with estimated development timelines

The MPCA specifically requests the public’s comments on these WQS projects.

Water quality standards: Active development

Group 1: Current and active. MPCA is committed to completing all these WQS projects.

1A: Rulemaking (minimum 18 months in this development stage)

  • Use Classes 3 (industrial) and 4 (agriculture and wildlife)

1B: Pre-rulemaking development (two to three years in this development stage)

  • Use Classes 2A (cold water)/2B (cool and warm water)
  • Use Class 1 (drinking water)

Water quality standards: Initial evaluation and development

Group 2: In technical development. MPCA anticipates making progress on these proposed WQS projects. 

2A: Technical review (one to two years in this development stage)

  • Revisions to Lake Eutrophication WQS
  • Nitrate – aquatic life
  • Ammonia – aquatic life
  • Perfluoro-octanesulfonic acid (PFOS) in fish tissue – human health
  • Aluminum, copper and cadmium – aquatic life

2B: Technical information outstanding (may not move into next phase before 2023)

  • Chloride  – aquatic life
  • Sulfate – aquatic life

Group 3: Tracking and evaluation. MPCA does not expect to make significant progress on these proposed WQS projects.

3. Tracking and evaluation (limited progress expected before 2023)

  • Revisions to Total Suspended Solids (TSS) WQS

Group 1A projects

Group 1A projects are in rulemaking and have an estimated timeline for adoption into state law. In this stage, the MPCA is responding to changes needed due to peer review (when applicable), finalizing the technical support document, and developing the Statement of Need and Reasonableness (SONAR) and final rule language. The need for peer review will affect the rulemaking timeline.

Use Classes 3 (industrial) and Class 4 (agriculture and wildlife)

Revision of the water quality standards and approach for protecting Class 3 (industrial) and Class 4 (agriculture and wildlife) use classes is a long-standing MPCA priority. The use classes are as follows:

  • Class 3 WQS protect waters for general industrial purposes, industrial cooling, and materials transport.
  • Class 4A WQS protect source waters used for irrigation purposes.
  • Class 4B WQS protect waters used for livestock and by wildlife.

These revisions incorporate the latest scientific understanding of how water quality affects its use for industrial and agricultural purposes (i.e., its beneficial uses). The rule revisions also provide clarity around implementation of the revised Class 3 and Class 4 WQS, particularly in terms of how wastewater permit conditions are derived and applied to facilities that discharge wastewater to waters designated with these beneficial uses.

A request for comment on the proposed amendments was published in the State Register on Dec. 14, 2020. A virtual public hearing is scheduled for Feb. 4, 2021; the initial comment period ends on Feb. 24, 2021.

Group 1B projects

For Group 1B projects, the agency has a basic concept of what may be included in the rule language and is preparing supporting documentation. Draft technical support documents for new or revised numeric standards go through an initial public comment period and independent peer review if required. When the technical support document is sufficiently complete, generally in two to three years, these pre-rulemaking projects will move into Group 1A and formal rulemaking.  

Use Classes 2A (cold waters) and 2B (cool and warm waters)

Revisions to Class 2A and 2B waters are needed to update and align these designations with the improved tools now used by MPCA to assess the condition of Minnesota’s waters, including the indices of biotic integrity and other biological criteria. This is the second set of revisions related to implementation of the Tiered Aquatic Life Use (TALU) framework, which added new Class 2 beneficial use tiers for aquatic life. It is anticipated that a request for comment for this rulemaking will be published before mid-year 2021.

Use Class 1 (drinking water)

Minn. R. ch. 7050 addresses drinking water use through the Class 1 Domestic Consumption designation, which applies to all groundwater and some surface waters. MPCA designates Class 1 waters and applies WQS following Minn. R. ch. 7050.0221, which predates inclusion of the federal Safe Drinking Water Act (SDWA) in the Clean Water Act and State Statute 103H (Groundwater Protection Act). Listings of Class 1 surface waters are in Minn. R. 7050.0470.

Class 1 revisions are needed to better define and protect waters used for domestic consumption (drinking water use and food processing), and address the inconsistencies and gaps in Minn. R. chs. 7050 and 7060 (underground waters). Revisions under consideration by MPCA include the following: 

  • Improving and clarifying Class 1 designations;
  • Updating numeric and narrative Class 1 WQS;
  • Adding language to address surface water and groundwater interaction; and
  • Consideration of the addition of Groundwater Contaminant Management Zones (GCMZs) to Minn. R. ch. 7060 to inform the public, state and local regulators, and others about areas of groundwater contamination.

Development of the revisions is continuing, along with discussions with the Minnesota Department of Health (MDH) and other state agency partners. More information on likely rule changes and supporting rationale will be available as progress is made, likely in mid-2021.

Group 2A projects

Group 2A projects are in technical development and have all the information needed from outside the MPCA to evaluate how the standard will address environmental or programmatic concerns, and to assess the resources needed to promulgate and implement the standard. To move the project into Group 1, the agency must determine if it's able to accommodate the added work of implementing a new WQS in addition to its regular permitting and related work. Group 2A projects are likely to move into Group 1B within one to two years.

Revisions to lake eutrophication WQS

This revision potentially includes several elements needed to update and modernize the eutrophication WQS for lakes.  They include: 1) revising the northern lake eutrophication standards by adding standards for a shallow lake type, 2) reviewing protections for cold water fish species including lake trout, lake whitefish, and cisco and developing standards where needed, 3) review and designation of cold water lakes, 4) adoption of a TALU framework for lakes, and 5) minor corrections and housekeeping revisions. It is anticipated that a request for comment for this rulemaking will be published before the end of 2021.


Development of a Class 2 aquatic life WQS for nitrate is a long-time priority. A draft technical support document for nitrate was developed and made available to the public in 2010. When EPA decided to pursue supplemental nitrate aquatic life toxicity tests, MPCA put further development of the WQS on hold. The EPA-sponsored toxicity studies are now mostly complete, such that MPCA can begin updating the 2010 technical support document and prepare to complete development of this standard. Additional information:    

Ammonia - aquatic life

Revision of the ammonia WQS to protect aquatic life has been a priority since 2013, when EPA issued a revised criteria for this pollutant. MPCA delayed this revision so it can be done in conjunction with development of the WQS for nitrate, which is a related, nitrogen-based pollutant.

HH-WQS for PFOS in fish tissue

Development of a statewide, fish-tissue based HH-WQS for perfluorooctanesulfonic acid (PFOS) is needed to address the large number of Minnesota waters that are impaired for PFOS in fish tissue. PFOS is an industrial pollutant that builds up (bioaccumulates) in fish and other aquatic life; Minnesota has been monitoring the presence of PFOS in fish tissue for several years.  

In 2020 MPCA developed an updated site-specific criteria for PFOS in fish tissue for Lake Elmo and connected waterbodies, Bde Maka Ska and Pool 2 of the Mississippi River. To develop a statewide WQS, additional development of the criteria and the associated fish consumption rate is needed; both will go through formal peer review prior to entering rulemaking.      

Aluminum, copper and cadmium WQS – aquatic life

EPA developed updated criteria for aluminum, copper and cadmium that reflect the latest scientific knowledge regarding the toxicity of these pollutants to aquatic life. The new criteria for aluminum and cadmium incorporate water hardness into the standard; the new criteria for copper is based on the biotic ligand model, which considers the amount of pollutant that is bioavailable and impacts aquatic life.    

These revisions are needed to maintain the scientific currency of Minnesota’s water quality standards.

Group 2B projects

Group 2B projects are in initial technical development, which typically  involves many tasks such as reviewing scientific literature, reviewing Minnesota-specific data, designing and undertaking studies, and(if available),reviewing and refining an EPA criteria document. Group 2B projects lack needed information to complete technical development and move to Group 2A. Because the information needs and technical approaches for developing WQS vary widely, it is difficult to estimate the time needed to advance these projects.

Chloride – aquatic life

The Class 2 aquatic life standard for chloride was selected for review and revision in previous triennial standard reviews because then new scientific information suggested Minnesota’s WQS was based on potentially outdated science. In the last several years, scientific studies have demonstrated that the interactions of ions (e.g., chloride, sulfate, calcium, and other ions) must be considered to accurately account for chloride’s toxicity. Currently, EPA is working to revise a previously developed chloride-sulfate model to incorporate the effects of hardness and potentially other ions on toxicity, based on results from the newest studies. MPCA is tracking EPA’s work on this model as well approaches being taken related to chloride by at least one other state. This project will move forward when there is better scientific agreement concerning a technical approach that accurately reflects chloride toxicity to aquatic life. 

Sulfate – aquatic life

Adding a Class 2 aquatic life standard for sulfate was selected in the last triennial standard review to add general aquatic life protection for sulfate to Minnesota’s WQS. As described above for chloride, scientific studies have demonstrated that the interactions of ions (e.g., chloride, sulfate, calcium, and other ions) must be considered to accurately account for sulfate’s toxicity. Currently, EPA is working to revise a previously developed chloride-sulfate model to incorporate the effects of hardness and potentially other ions on toxicity, based on results from the newest studies. This project will move forward when there is better scientific agreement concerning a technical approach that accurately reflects sulfate toxicity to aquatic life. 

Group 3 projects

The MPCA has not started developing Group 3 projects, because of missing technical information, a lack of capacity, or both. Group 3 projects are likely to proceed to standard development, but they may remain in Group 3 without significant progress towards regulatory development throughout the three year triennial period.

Revisions to river total suspended solids (TSS) WQS – aquatic life

This revision may be needed to account for rivers that have naturally high TSS and also high quality biological communities (e.g. rivers in glacial lake beds where the soil can have high silt and clay content). A thorough review of Minnesota’s TSS and biological monitoring data (fish and invertebrates) must be completed prior to moving forward with this project, to ascertain the basis and likely approach for the revision. This review will be accomplished as staff availability allows.