30 Tex. Admin. Code § 334.606
Owners and operators of underground storage tank facilities (except unmanned facilities) must maintain required training certification documentation as described in § 334.603(b) of this title (relating to Acceptable Operator Training and Certification Processes) on-site and must provide it upon request to a Texas Commission on Environmental Quality (TCEQ) or TCEQ-authorized investigator. Documentation may be maintained electronically off-site if that facility has the capability of producing a clear printed copy which can be provided to a TCEQ or TCEQ-authorized investigator within 72 hours of the time of the investigation. Owners and operators of unmanned facilities must provide documentation as requested by a TCEQ investigator or TCEQ-authorized investigator.
30 Tex. Admin. Code § 334.606