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Water: State, Tribal & Territorial Standards

Repository of Documents: Montana

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Water Quality Standards Provisions in Montana's Water Quality Act, Title 75 - Environmental Protection, Chapter 5 - Water Quality (PDF) (58 pp, 193K)
(Effective August 17, 2004) 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) (14 pp, 46K)
(Effective August 17, 2004) This subchapter contains rules governing the granting of mixing zones.
Surface Water Quality Standards and Procedures - Sub-chapter 6 (17.30.601–17.30.646) (PDF) (50 pp, 175K)
(Effective September 4, 2008) 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) (24 pp, 76K)
(Effective August 17, 2004) 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) (76 pp, 702K)
(Effective May 11, 2015) This document contains numeric water quality criteria for Montana surface and ground waters.
Circular DEQ-12A, Montana Base Numeric Nutrient Standards (PDF) (11 pp, 211K)
(Effective February 26, 2015) 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) (9 pp, 190K)
(Effective February 26, 2015) 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.

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.

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