17.30.621 A-CLOSED CLASSIFICATION STANDARDS
(1) Waters classified A-Closed are to be maintained suitable for drinking, culinary, and food processing purposes after simple disinfection. Water quality is to be maintained suitable for swimming, recreation, growth, and propagation of fishes and associated aquatic life, although access restrictions to protect public health may limit actual use of A-Closed waters for these uses.
(2) Public access and activities such as livestock grazing and timber harvest are to be controlled by the utility owner under conditions prescribed and orders issued by the department.
(3) No person may violate the following specific water quality standards for waters classified A-Closed:
(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. 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) No change from naturally occurring dissolved oxygen levels is allowed.
(c) No change from natural pH is allowed.
(d) No increase above naturally occurring turbidity is allowed except as permitted in 75-5-318, MCA.
(e) No increase above naturally occurring water temperature is allowed.
(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) No increase in true color is allowed.
(h) No increases of carcinogenic, bioconcentrating, toxic or harmful parameters, pesticides, and organic and inorganic materials, including heavy metals, above naturally occurring concentrations, are allowed.
(i) No increase in radioactivity above natural background levels is allowed.
History: 75-5-201, 75-5-301, MCA; IMP, 75-5-301, MCA; Eff. 12/31/72; AMD, Eff. 11/4/73; AMD, Eff. 9/5/74; AMD, 1980 MAR p. 2252, Eff. 8/1/80; AMD, 1988 MAR p. 1191, Eff. 6/10/88; AMD, 1994 MAR p. 2136, Eff. 8/12/94; TRANS, from DHES, and AMD, 1996 MAR p. 1499, Eff. 6/7/96; AMD, 2002 MAR p. 387, Eff. 2/15/02; AMD, 2006 MAR p. 528, Eff. 2/24/06; AMD, 2017 MAR p. 602, Eff. 5/13/17.