The following definitions, in addition to those in 75-5-103, MCA, and ARM Title 17, chapter 30, subchapters 6 and 7, apply throughout this subchapter:

1. (1) "Acute toxicity" means a condition in which ambient water concentrations exceed the applicable acute aquatic life standards given in department Circular DEQ-7.
2. (2) "Chronic toxicity" means a condition in which ambient water concentrations exceed the applicable chronic aquatic life standards given in department Circular DEQ-7.
3. (3) "Constructed wetland" means a wetland intentionally designed, constructed and operated for the primary purpose of wastewater or stormwater treatment or environmental remediation.
4. (4) "Currently available data" means data that is readily available to the department at the time a decision is made. It does not mean new data to be obtained as a result of departmental efforts or required of the applicant.
5. (5) "Human health standard" means the parameters listed as human health standards in department Circular DEQ-7.
6. (6) "Mixing zone" is defined in 75-5-103 , MCA, and also means a limited area of a surface water body or a portion of an aquifer, where initial dilution of a discharge takes place and where water quality changes may occur and where certain water quality standards may be exceeded.
7. (7) "Nearly instantaneous mixing zone" means an area where dilution of a discharge to water by the receiving water occurs at a nearly instantaneous rate, with the result that its boundaries are either at the point of discharge or are within two stream widths downstream of the point of discharge.
8. (8) "Narrative standards" means those parameters listed as narrative standards in department Circular DEQ-7.
9. (9) "Numeric acute standards" means the parameters listed as acute aquatic life standards in department Circular DEQ-7.
10. (10) "Numeric chronic standards" means the parameters listed as chronic aquatic life standards in department Circular DEQ-7.
11. (11) "Standard mixing zone" means a mixing zone that meets the requirements of ARM 17.30.516 and 17.30.517 and involves less data collection and demonstration than required for a source specific mixing zone.
12. (12) "Wetlands" means those areas that are inundated or saturated by surface or ground water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions.
13. (13) "Zone of influence" means the area under which a well can be expected to remove water.
14. (14) The department adopts and incorporates by reference Department Circular DEQ-7, entitled "Montana Numeric Water Quality Standards" (June 2019 edition), which establishes numeric water quality standards for toxic, carcinogenic, bioconcentrating, nutrient, radioactive, and harmful parameters. Copies of Department Circular DEQ-7 are available from the Department of Environmental Quality, P.O. Box 200901, Helena, MT 59620-0901.

Authorizing statute(s): 75-5-301, MCA

Implementing statute(s): 75-5-301, MCA

History: NEW, 1994 MAR p. 2136, Eff. 8/12/94; AMD, 1995 MAR p. 1798, Eff. 9/15/95; AMD, 1996 MAR p. 555, Eff. 2/23/96; TRANS, from DHES, 1996 MAR p. 1499; AMD, 1998 MAR p. 2487, Eff. 9/11/98; AMD, 2002 MAR p. 387, Eff. 2/15/02; AMD, 2003 MAR p. 217, Eff. 2/14/03; AMD, 2004 MAR p. 725, Eff. 4/9/04; AMD, 2006 MAR p. 528, Eff. 2/24/06; AMD, 2008 MAR p. 946, Eff. 5/9/08; AMD, 2010 MAR p. 1796, Eff. 8/13/10; AMD, 2012 MAR p. 2060, Eff. 10/12/12; AMD, 2017 MAR p. 602, Eff. 5/13/17; AMD, 2019 MAR p. 826, Eff. 6/22/19; AMD, 2024 MAR p. 257, Eff. 2/10/24.