1. a) During the months May through October, based on a minimum of five samples taken over not more than a 30-day period, fecal coliform must not exceed a geometric mean of 200 per 100 milliliters (ml), nor must more than 10% of the samples during any 30-day period exceed 400 per 100 ml in protected waters. Protected waters are defined as waters that, due to natural characteristics, aesthetic value, or environmental significance, deserve protection from pathogenic organisms. Protected waters will meet one or both of the following conditions:

   1. 1) presently support or have the physical characteristics to support primary contact;
   2. 2) flow through or adjacent to parks or residential areas.
2. b) Waters unsuited to support primary contact uses because of physical, hydrologic, or geographic configuration and that are located in areas unlikely to be frequented by the public on a routine basis as determined by the Agency at 35 Ill. Adm. Code 309.Subpart A are exempt from this standard.
3. c) The Agency must apply this rule as required by 35 Ill. Adm. Code 304.121.

(Source: Amended at 47 Ill. Reg. 4437, effective March 23, 2023)