Ill. Admin. Code tit. 35, pt. 375

Combined Sewer Overflow Exception Criteria and First Flush Determination

AUTHORITY: Implementing and authorized by Sections 4 and 12(a) of the Environmental Protection Act [415 ILCS 5/4 and 5/12.2]. SOURCE: Adopted and Codified at 7 Ill. Reg. 10808, effective August 23, 1983; amended at 8 Ill. Reg. 19436, effective September 26, 1984; amended at 49 Ill. Reg. 16200, effective December 4, 2025.ENVIRONMENTAL PROTECTION AGENCY

375.101Policy 375.102Definitions 375.103Prohibitions 375.201Policy 375.202Phase I – Background Information 375.203Phase II – Preliminary Stream Inspection 375.204Phase III – Detailed Water Quality Evaluation 375.205Special Analysis for Congested Areas 375.206Time Schedule 375.301Water Quality Evaluation 375.302Control Alternatives 375.303Benefits Assessment 375.401Variables in First Flush Determination 375.402Conditions for Determination 375.403Field Studies 375.404Modeling 375.APPENDIX AFirst Flush Graph