415 ILCS 160/20
A person who operates an underground natural gas storage facility shall file with the Department a plan for inspection and maintenance of the downhole portion of each underground natural gas storage facility owned or operated by the person, as well as any changes in the plan, in accordance with rules prescribed by the Department. The Department may, by rule, also require the person to file the plan for approval. If the Department finds, at any time, that the plan is inadequate to achieve safe operation, the Department shall, after notice and opportunity for a hearing, require the plan to be revised. The plan required by the Department under this Section must be practicable and designed to meet the need for the safety of underground natural gas storage facilities. In determining the adequacy of a plan, the Department shall consider: (i) relevant available underground natural gas storage facility safety data; (ii) whether the plan is appropriate for the particular type of facility; (iii) the reasonableness of the plan; and (iv) the extent to which the plan will contribute to public safety.
415 ILCS 160/20