30 Tex. Admin. Code § 335.158
The owner or operator must comply with conditions specified in the facility permit that are designed to ensure that hazardous constituents under § 335.159 of this title (relating to Hazardous Constituents) which have been detected in the groundwater from a regulated unit do not exceed the concentration limits under § 335.160 of this title (relating to Concentration Limits) in the uppermost aquifer underlying the waste management area beyond the point of compliance during the compliance period under § 335.162 of this title (relating to Compliance Period). The commission will establish this groundwater protection standard in the compliance plan when hazardous constituents have been detected in the groundwater from a regulated unit.
30 Tex. Admin. Code § 335.158