Ill. Admin. Code tit. 2, § 3700.400
a) Filing Documents with the Agency
b) For all agency inquiries other than filing of documents as described in subsection (a) or petitions for rulemaking pursuant to Section 3700.300, any interested person may contact the Agency through its website set out in Section 3700.410 or by U.S. mail to:
Illinois Power Agency
Michael A. Bilandic Building
160 N. LaSalle St., Suite C-504
Chicago IL 60601