Administrative Rules of Montana › Department 17 - ENVIRONMENTAL QUALITY › Chapter 17.30 - WATER QUALITY › Subchapter 17.30.5 - Mixing Zones in Surface and Ground Water › Rule 17.30.502 - DEFINITIONS

Current through Register Vol. 13, July 5, 2024
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) "Acute toxicity" means a condition in
				which ambient water concentrations exceed the applicable acute aquatic life
				standards given in department Circular DEQ-7.
(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) "Constructed wetland" means a wetland
				intentionally designed, constructed and operated for the primary purpose of
				wastewater or stormwater treatment or environmental remediation.
(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)
				"Human health standard" means the parameters listed as human health standards
				in department Circular DEQ-7.
(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) "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) "Narrative
				standards" means those parameters listed as narrative standards in department
				Circular DEQ-7.
(9) "Numeric acute
				standards" means the parameters listed as acute aquatic life standards in
				department Circular DEQ-7.
(10)
				"Numeric chronic standards" means the parameters listed as chronic aquatic life
				standards in department Circular DEQ-7.
(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)
				"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) "Zone of influence" means the area under
				which a well can be expected to remove water.
(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.
AUTH:
					 75-5-301, MCA; IMP:
					 75-5-301,
					 MCA