Water Quality Standards Regulations: Montana
Presented are water quality standards in effect for Clean Water Act (CWA) purposes for this state.
EPA is posting these standards as a convenience to users and has made a reasonable effort to assure their accuracy. For each document listed under "State Standards in Effect for CWA Purposes", EPA has made a reasonable effort to identify parts of the standards that are disapproved or are otherwise not in effect for CWA purposes. Additionally, please note the documents may also contain provisions that EPA does not have the authority and duty to act on under the Clean Water Act because the provisions are not water quality standards.
State Standards in Effect for CWA Purposes
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Water Quality Standards Provisions in Montana's Water Quality Act, Title 75 - Environmental Protection, Chapter 5 - Water Quality (75.5.101–75.5.327) (pdf)
These are the water quality standards enacted by Montana State legislature. -
Mixing Zones in Surface and Ground Water - Sub-chapter 5 (17.30.501–17.30.518) (pdf)
This subchapter contains rules governing the granting of mixing zones. -
Surface Water Quality Standards and Procedures - Sub-chapter 6 (17.30.601–17.30.670) (pdf)
This subchapter contains water use classifications for waters of the state. -
Nondegradation of Water Quality - Sub-chapter 7 (17.30.701–17.30.717) (pdf)
This subchapter contains the implementation procedures for implementing the nondegradation policy contained in 75-5-303 of Montana's Water Quality Act. -
Circular DEQ-7, Montana Numeric Water Quality Standards (pdf)
This document contains numeric water quality criteria for Montana surface and ground waters. -
Circular DEQ-12A, Montana Base Numeric Nutrient Standards (pdf)
This document contains information pertaining to the base numeric nutrients standards and their implementation. This information includes the standards’ concentration limits, where the standards apply, and their period of application. -
Circular DEQ-12B, Montana Nutrient Standards Variances (pdf)
This document contains information about variances from the base numeric nutrient standards. This information includes details on effluent treatment requirements associated with general nutrient standards variances, as well as effluent treatment requirements for individual nutrient standards variances and to whom they apply.- Please refer to EPA's recent action: EPA Action in Response to Court Order in Upper Missouri Waterkeeper v. EPA (D. Mont. No. 4:16-cv-00052-BMM) dated 2/24/20 (pdf)
Montana's water quality standards are applicable to "waters of the State". In some limited instances, the definition adopted by Montana for "waters of the State" as part of its water quality standards may result in water quality standards that are more comprehensive than required under section 303(c) of the Clean Water Act and the implementing federal regulations. Specifically, Montana has adopted additional provisions related to groundwater that are outside the scope of the Clean Water Act and implementing federal regulations. EPA has included the State's water quality standards in their entirety here for context and as supplementary information for the reader.
Montana water quality standards apply to all waters within the State of Montana, with the exception of those waters that are within Indian Country, as defined in 18 U.S.C. Section 1151. EPA's approval of Montana's water quality standards was not intended as an action to approve or disapprove water quality standards applying to waters within Indian Country. EPA, or eligible Indian Tribes, as appropriate, will retain responsibilities for water quality standards within Indian Country.
Federally Proposed or Promulgated Standards
- None at this time.