9 Va. Admin. Code § 25-260-70
The maximum hourly temperature change shall not exceed 2°C, except in the case of Class VI waters (natural trout waters) where it shall not exceed 0.5°C. These criteria shall apply beyond the boundaries of mixing zones and are in addition to temperature changes caused by natural conditions.
§ 62.1-44.15(3a) of the Code of Virginia.
Derived from VR680-21-01.7, eff. May 20, 1992; amended, Virginia Register Volume 14, Issue 4, eff. December 10, 1997.