020-1 Wyo. Code R. § 1-25
(a) For Class 1, 2 and 3 waters, pollution attributable to the activities of man shall not change ambient water temperatures to levels which result in harmful acute or chronic effects to aquatic life, or which would not fully support existing and designated uses.
(b) When ambient temperatures are above 60 degrees Fahrenheit (15.6 degrees Celsius) in all Class 1, 2AB and 2B waters which are cold water fisheries, pollution attributable to the activities of man shall not result in an increase of more than 2 degrees Fahrenheit (1.1 degree Celsius) in existing temperatures.
(c) When ambient temperatures are above 60 degrees Fahrenheit (15.6 degrees Celsius) in all Class 1, 2AB, 2B and 2C waters which are warm water fisheries, pollution attributable to the activities of man shall not result in an increase of more than 4 degrees Fahrenheit (2.2 degrees Celsius) in existing temperatures.
(d) Except on Class 2D, 3 and 4 waters, the maximum allowable stream temperature will be the maximum natural daily stream temperature plus the allowable change, provided that this temperature is not lethal to existing fish life and under no circumstance shall pollution attributable to the activities of man result in a temperature that exceeds 68 degrees Fahrenheit (20 degrees Celsius) in the case of cold water fisheries and 86 degrees Fahrenheit (30 degrees Celsius) in the case of warm water fisheries.
(e) With the exception of the provisions of Sections 9 and 11 of these regulations and other natural conditions, temperature standards shall apply at all times and at all depths of the receiving water and may not be violated at any time or at any depth.
(f) The various requirements of this section may be waived only under the provisions of Section 316(a) of the Clean Water Act.
020-1 Wyo. Code R. § 1-25
Amended, Eff. 4/24/2018.