Section 375.402  Conditions for Determination

For any given sewer system, or portion of a sewer system, first flush volume subject to full treatment requirements of 35 Ill. Adm. Code 306.305(a) and associated flow rate shall be determined for the following condition(s):

a)         A storm of 1.2 inch per hour intensity with a duration of 60 minutes, which approximates a one year-one-hour storm for most sections of the state.

b)         There shall be sufficient time between the storm event chosen to determine first flush and any previous event to allow for adequate solids deposition in the sewers and on the streets to demonstrate first flush under this Part.  In general a ten day period should be sufficient.

(Source:  Added at 8 Ill. Reg. 19436, effective September 26, 1984)