a) This Part applies to proceedings before the Board in which:

1. 1) Any person seeks, under the Environmental Protection Act [415 ILCS 5] or the Groundwater Protection Act [415 ILCS 55], to require another person to perform, or to recover the costs of, a response that results from a release or substantial threat of a release of regulated substances or pesticides on, in, under or from a site; or
2. 2) Two or more persons seek to allocate among themselves 100 percent of the performance or costs of a response that results from a release or substantial threat of a release of regulated substances or pesticides on, in, under or from a site.

d) Subpart B of this Part applies when a complaint is filed with the Board that seeks, under the Environmental Protection Act or the Groundwater Protection Act:

1. 1) To require any person to perform a response that results from a release or substantial threat of a release of regulated substances or pesticides; or
2. 2) To recover the costs of a response that results from a release or substantial threat of a release of regulated substances or pesticides.

f) This Part does not apply to:

1. 1) Any cost recovery action brought by the State under Section 22.2 of the Act to recover costs incurred by the State prior to July 1, 1996 (Section 58.9(f) of the Act);
2. 2) Sites on the National Priorities List (Appendix B of 40 CFR 300);
3. 3) Sites where a federal court order or a United States Environmental Protection Agency order requires an investigation or response;

4. 4) The owner or operator of a treatment, storage or disposal site:

   1. A) For which a current permit has been issued or is required under federal or State solid or hazardous waste laws; or
   2. B) That is subject to closure or corrective action requirements under federal or State solid or hazardous waste laws;
5. 5) The owner or operator of an underground storage tank system subject to federal or State underground storage tank laws.