Tex. Nat. Res. Code § 91.1012
Members and employees of the commission, on proper identification, may enter public or private property to inspect and investigate conditions relating to the quality of water in the state, to inspect and investigate conditions relating to development of rules, orders, or permits issuable under Section 91.101 of this code, to monitor compliance with a rule, permit, or other order of the commission, or to examine and copy, during reasonable working hours, those records or memoranda of the business being investigated. Members or employees acting under the authority of this section who enter an establishment on public or private property shall observe the establishment's safety, internal security, and fire protection rules.
Tex. Nat. Res. Code § 91.1012