Section 306.305  Treatment of Overflows and Bypasses

All combined sewer overflows and treatment plant bypasses must be given sufficient treatment to prevent pollution or the violation of applicable water quality standards unless an exception has been granted by the Board.  Sufficient treatment consists of the following:

a)         All dry weather flows, and the first flush of storm flows as determined by the Agency, must meet the applicable effluent standards; and

b)         Additional flows, as determined by the Agency but not less than ten times the average dry weather flow for the design year, must receive a minimum of primary treatment and disinfection with adequate retention time; and

c)         Flows exceeding those described in subsection (b) must be treated, in whole or in part, to the extent necessary to prevent any accumulation of sludge deposits, floating debris, and solids in compliance with 35 Ill. Adm. Code 302.203 and to prevent depression of oxygen levels; or

d)         Compliance with a treatment program authorized by the Board in an exception proceeding.

(Source:  Amended at 47 Ill. Reg. 4641, effective March 23, 2023)