1. a) For a unit subject to Subpart E (land treatment units) or Subpart F (surface impoundments), samples must be collected at least quarterly and analyzed for pH, specific conductance, total organic carbon, total organic halogen, and any other parameter that meets the following criteria:

   1. 1) Material containing the parameter is stored, treated, or disposed of at the unit; and
   2. 2) The Board has adopted a groundwater standard for the parameter.

2. b) For a unit subject to Subpart I for the storage and handling of pesticides, samples must be collected at least quarterly, except as provided in subsection (d), and analyzed for the five specific pesticides or five groups of chemically similar pesticides stored or handled at the unit that are the most likely to enter into the groundwater from the unit and that are the most toxic. The owner or operator must choose the five specific pesticides or five groups based upon the following criteria:

   1. 1) The volume of the pesticides stored or handled at the unit;
   2. 2) The leachability characteristics of the pesticides stored or handled at the unit;
   3. 3) The toxicity characteristics of the pesticides stored or handled at the unit;
   4. 4) The history of spillage of the pesticides stored or handled at the unit; and
   5. 5) Any groundwater standards for the pesticides stored or handled at the unit.
3. c) For a unit subject to Subpart J for the storage and handling of fertilizer, samples must be collected at least quarterly, except as provided in subsection (d), and analyzed for pH, total organic carbon, nitrates as nitrogen, ammonia nitrogen, and specific conductance.

4. d) Despite subsections (b) and (c), for a unit subject to Subpart I for the storage and handling of pesticides or a unit subject to Subpart J for the storage and handling of fertilizers, samples must be collected at least semi-annually if all of the following conditions are met:

   1. 1) The unit is in compliance with the containment requirements of 8 Ill. Adm. Code 255; and
   2. 2) There have been no detections within the preceding two years in any of the monitoring wells of any contaminant stored or handled at the facility or any contaminant attributable to the operation of the unit.
5. e) For a unit subject to Subpart K for the storage and handling of road oils or subject to Subpart L for the storage and handling of de-icing agents, samples must be collected annually and analyzed for pH, specific conductance, total organic carbon, and total organic halogen.

Upon completion of the background sampling required under Section 616.207, the owner or operator must sample each monitoring well for the duration of the compliance period and analyze each sample, except as provided in Section 616.209, according to the following program:

(Source: Amended at 47 Ill. Reg. 7631, effective May 16, 2023)