a) Participants that agree to accept 100 percent of liability to perform or pay for 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, whether or not they stipulate to specific shares of such liability, may initiate a voluntary allocation proceeding by filing a petition with the Board if:

1. 1) There is an Agency-approved Remedial Action Plan for the site under 35 Ill. Adm. Code 740; or
2. 2) There is a written agreement with the Agency regarding the performance of a response at the site following the issuance of a notice under Section 4(q) or Section 58.9(b) of the Act.

b) The petition under subsection (a) of this Section must include the following information:

1. 1) The location and identity of the site for which an allocation of proportionate shares is requested;
2. 2) The identity of all participants;
3. 3) The stipulated shares of specific participants, if any;
4. 4) Certification that the participants agree to allocate among themselves 100 percent of the performance or costs of the response under the Remedial Action Plan or written agreement with the Agency; and
5. 5) A statement that the participants choose to engage in either mediation under Sections 741.320 and 741.325 of this Subpart or to proceed with the Board's allocation proceedings under Sections 741.310 and 741.315 of this Subpart.