Iowa Admin. Code r. 141-5.2
5.2(3) Action on petition. Within 60 days after filing of the petition, or within any longer period agreed to by the petitioner, the agency shall either deny the petition and notify the petitioner of the denial and the grounds for the denial, or grant the petition, notify the petitioner that the petition has been granted, and adopt a rule on the subject of the petition. Petitioner is deemed notified on the date the agency mails or delivers the required notification to the petitioner.