Approval to construct shall become invalid if construction is not commenced within 18 months after receipt of approval, if construction is discontinued for a period of 18 months or more, or if construction is not completed within a reasonable time. The Agency may extend the 18-month period upon a satisfactory showing that an extension is justified. This provision does not apply to the time period between construction of the approved phases of a phased construction project; each phase must commence construction within 18 months after the projected and approved commencement date.
Ill. Admin. Code tit. 35, § 204.830