Administrative Rules of Montana › Department 17 - ENVIRONMENTAL QUALITY › Chapter 17.30 - WATER QUALITY › Subchapter 17.30.6 - Surface Water Quality Standards and Procedures › Rule 17.30.622 - A-1 CLASSIFICATION STANDARDS

Current through Register Vol. 13, July 5, 2024
(1) Waters
				classified A-1 are to be maintained suitable for drinking, culinary and food
				processing purposes after conventional treatment for removal of naturally
				present impurities.
(2) Water
				quality must be maintained suitable for bathing, swimming, and recreation;
				growth and propagation of salmonid fishes and associated aquatic life,
				waterfowl and furbearers; and agricultural and industrial water
				supply.
(3) No person may violate
				the following specific water quality standards for waters classified A-1:
(a) The geometric mean number of Escherichia
				coli bacteria may not exceed 32 colony forming units per 100 milliliters and 10
				percent of the samples may not exceed 64 colony forming units per 100
				milliliters during any 30-day period if resulting from domestic sewage. Water
				quality criteria for Escherichia coli are expressed in colony forming units per
				100 milliliters of water or as most probable number, which is a statistical
				representation of the number of organisms in a sample, as incorporated by
				reference in 40 CFR
				136.3(b).
(b) Dissolved oxygen concentration must not
				be reduced below the applicable standards given in department Circular
				DEQ-7.
(c) Induced variation of
				hydrogen ion concentration (pH) within the range of 6.5 to 8.5 must be less
				than 0.5 pH unit. Natural pH outside this range must be maintained without
				change. Natural pH above 7.0 must be maintained above 7.0.
(d) No increase above naturally occurring
				turbidity or suspended sediment is allowed except as permitted in
				75-5-318, MCA.
(e) A 1ºF maximum increase above
				naturally occurring water temperature is allowed within the range of 32ºF
				to 66ºF; within the naturally occurring range of 66ºF to 66.5ºF,
				no discharge is allowed which will cause the water temperature to exceed
				67ºF; and where the naturally occurring water temperature is 66.5ºF
				or greater, the maximum allowable increase in water temperature is 0.5ºF.
				A 2ºF-per-hour maximum decrease below naturally occurring water
				temperature is allowed when the water temperature is above 55ºF. A
				2ºF maximum decrease below naturally occurring water temperature is
				allowed within the range of 55ºF to 32ºF.
(f) No increases are allowed above naturally
				occurring concentrations of sediment or suspended sediment (except as permitted
				in 75-5-318, MCA), settleable solids,
				oils, or floating solids, which will or are likely to create a nuisance or
				render the waters harmful, detrimental, or injurious to public health,
				recreation, safety, welfare, livestock, wild animals, birds, fish, or other
				wildlife.
(g) True color must not
				be increased more than two color units above naturally occurring
				color.
(h) Concentrations of
				carcinogenic, bioconcentrating, toxic, radioactive, nutrient, or harmful
				parameters may not exceed the applicable standards set forth in Department
				Circular DEQ-7 and, unless a nutrient standards variance has been granted,
				Department Circular DEQ-12A.
(i)
				Dischargers issued permits under ARM Title 17, chapter 30, subchapter 13, shall
				conform with ARM Title 17, chapter 30, subchapter 7, the nondegradation rules,
				and may not cause receiving water concentrations to exceed the applicable
				standards contained in Department Circular DEQ-7 and, unless a nutrient
				standards variance has been granted, Department Circular DEQ-12A when stream
				flows equal or exceed the design flows specified in ARM
				17.30.635(2).
(j) If site-specific criteria for
				aquatic life are adopted using the procedures given in
				75-5-310, MCA, the criteria shall
				be used as water quality standards for the affected waters and as the basis for
				permit limits instead of the applicable standards in Department Circular
				DEQ-7.
(k) In accordance with
				75-5-306(1), MCA,
				it is not necessary that wastes be treated to a purer condition than the
				natural condition of the receiving water as long as the minimum treatment
				requirements, adopted pursuant to
				75-5-305, MCA, are met.