Section 303.341  Mississippi River North Central Temperature

Instead of the standards of 35 Ill. Adm. Code 302.211(e), the water temperature at representative locations in the main river of the Mississippi River in the indicated locations must not exceed the maximum limits in the following tables during more than 1% of the hours in the 12-month period ending with any month.  The water temperature at these locations must not at any time exceed the maximum limits in the following table by more than 1.7 ºC (3 ºF).

a)         In the Mississippi River from the Rock River to the Iowa/Missouri border:

b)         In the Mississippi River from the Iowa/Missouri border to the Illinois River:

(Source:  Amended at 47 Ill. Reg. 4575, effective March 23, 2023)