35 Ill. Adm. Code 302.502
Dissolved Oxygen
Section 302
Section 302.502Â Dissolved
Oxygen
Dissolved oxygen must not be
less than 90% of saturation, except due to natural causes, in the Open Waters
of Lake Michigan as defined at Section 302.501. The other waters of the Lake
Michigan Basin must not be less than 6.0 mg/L during at least 16 hours of any
24 hour period, nor less than 5.0 mg/L at any time.