Amendments to Water Quality Standards: Use classifications 3 and 4

The Clean Water Act requires a regular review of state water quality standards, and one important aspect of that review is the updating of designated use classifications. In this rulemaking, the MPCA proposes to amend the existing rules governing water quality standards for industrial consumption (Class 3) and agricultural and wildlife usage (Class 4). Please note that this rulemaking will not address the Class 4A wild rice sulfate standard, which is the subject of a separate rulemaking effort.

Summary of changes

  • replace numeric standards for existing subclasses 3A–3D with a single narrative standard, condensing the subclasses into a single industrial consumption use class;
  • replace numeric Class 4A standards for bicarbonate, boron, pH, specific conductance, total dissolved salts and sodium with a narrative standard and include a process to translate the narrative standard into a numeric effluent limit or limits for permitted dischargers;
  • update numeric standards for Class 4B to reflect current science;
  • remove the Class 4C designated use (protection of wetlands for agriculture and wildlife) and designate wetlands as Classes 4A and 4B instead of 4C;
  • move wetland standards for chloride and settleable solids from Classes 3D and 4C to Class 2D, and move the narrative Class 4C standard to 7050.0186, to more appropriately reflect the uses being protected; and
  • maintain applicability of Class 3, 4A, and 4B uses on all waters of the state.

Learn more: PDF icon Making changes to Class 3 and 4 standards will protect state waters while lowering regulatory hurdles (wq-rule4-17e)

Rulemaking and technical support documents

2019 Request for comments

2016 Request for comments

2010 Evaluation from the University of Minnesota’s Department of Bioproducts and Biosystems Engineering.

Draft rule language

Not yet available.

You can register at GovDelivery to be notified when draft rule language is published.

Schedule/public participation opportunities

Register at GovDelivery to receive notice of upcoming Use Class 3 and 4 rulemaking activities.

First request for comments Published February 8, 2016; comment period ended April 8, 2016
Second request for comments Published March 11, 2019; comment period ended April 22, 2019
Public comment period/Notice of hearing See docket: PDF icon Public Rulemaking Docket (mm-rule1-00)
Post–comment period/Administrative Law Judge review To be determined
Adoption of rules See docket: PDF icon Public Rulemaking Docket (mm-rule1-00)
U.S. Environmental Protection Agency review and approval To be determined


Contact information

For questions about the status of the rulemaking or how to submit comments:
Yolanda Letnes:, 651-757-2527

For technical questions about these use classifications and the proposed changes:
Scott Kyser:, 651-757-2665