1. a) 35 Ill. Adm. Code 307 includes three types of prohibitions and pretreatment standards:

   1. 1) Prohibitions, including prohibitions adopted by USEPA at 40 CFR 403.5 and more stringent prohibitions adopted by the Board (e.g., 35 Ill. Adm. Code 307.1101);
   2. 2) National pretreatment standards adopted by USEPA at 40 CFR 405 et seq., and incorporated by reference by the Board (e.g., Subparts F through CT of 35 Ill. Adm. Code 307); and
   3. 3) More stringent concentration-based standards adopted by the Board (e.g., 35 Ill. Adm. Code 307.1102 and 307.1103).

2. b) For subcategories for which there are both categorical pretreatment standards and concentration-based standards adopted by the Board for a pollutant, the Control Authority must apply the standard that is more stringent as applied to the particular discharge.

   BOARD NOTE: Derived from 40 CFR 403.4 (2003).

(Source: Amended at 47 Ill. Reg. 5083, effective March 23, 2023)