Section 302.507  Thermal Standards for Existing Sources on January 1, 1971

All sources of heated effluents in existence as of January 1, 1971, must meet the following restrictions outside of a mixing zone that is no greater than a circle with a radius of 305 m (1000 feet) or an equal fixed area of simple form.

a)         There must be no abnormal temperature changes that may affect aquatic life.

b)         The normal daily and seasonal temperature fluctuations that existed before the addition of heat must be maintained.

c)         The maximum temperature rise at any time above natural temperatures must not exceed 1.7 ºC (3 ºF).  In addition, the water temperature must not exceed the maximum limits indicated in the following table:

(Source:  Amended at 47 Ill. Reg. 4437, effective March 23, 2023)