Ill. Admin. Code tit. 62, § 245.620
b) Unless rebutted by a defense established in subsection (c), it shall be presumed that any person conducting or who has conducted high volume horizontal hydraulic fracturing operations shall be liable for pollution or diminution of a water supply if (Section 1-85(b) of the Act):
c) To rebut the presumption established under this Section, a person presumed responsible must affirmatively prove by clear and convincing evidence any of the following (Section 1-85(c) of the Act):