Unless corrective action is initiated in accordance with §§334.76 - 334.81 of this title (relating to Initial Response to Releases; Initial Abatement Measures and Site Check; Site Assessment; Removal of Non-Aqueous Phase Liquids (NAPLs); Investigation for Soil and Groundwater Cleanup; and Corrective Action Plan), owners or operators must immediately investigate and confirm all suspected releases of regulated substances requiring reporting under §334.72 of this title (relating to Reporting of Suspected Releases) within 30 days, using either the following steps or another procedure and schedule approved or required by the agency.
  (1) System test. Owners or operators must conduct tests according to the requirements for tightness testing in §334.50 of this title (relating to Release Detection) and secondary containment testing described in §334.48(e) of this title (relating to General Operating and Management Requirements), as appropriate.
    (A) The test must determine whether:
      (i) a leak exists in the portion of the tank that routinely contains product or the attached delivery piping; or
      (ii) a breach of either wall of the secondary containment has occurred.
    (B) If the system test confirms a leak into the interstice or a release, owners and operators must repair, replace, or close the aboveground storage tank (AST) or underground storage tank (UST) system, and begin corrective action in accordance with §§334.76 - 334.81 of this title if the test results for the system, tank, or delivery piping indicate that a leak exists.
    (C) Further investigation is not required if the test results for the system, tank, and delivery piping do not indicate that a leak exists and if environmental contamination is not the basis for suspecting a release.
    (D) Owners and operators must conduct a site check as described in paragraph (2) of this section if the test results for the system, tank, and delivery piping do not indicate that a leak exists but environmental contamination is the basis for suspecting a release.
  (2) Site check. Owners and operators must measure for the presence of a release where contamination is most likely to be present at the AST or UST site. In selecting sample types, sample locations, and measurement methods, owners and operators must consider the nature of the stored substance, the type of initial alarm or cause for suspicion, the type of backfill, the depth to groundwater, and other factors appropriate for identifying the presence and source of the release.
    (A) If the test results from an excavated area, or other area(s) of the AST or the UST site indicate that a release has occurred, owners and operators must begin corrective action in accordance with §§334.76 - 334.81 of this title.
    (B) If the test results from an excavated area, or other area(s) of the AST or UST site do not indicate that a release has occurred, further investigation is not required.
  (3) In the event there is no evidence of a release after performing the tests required in paragraphs (1) and (2) of this section, the owner or operator must file a report which contains a detailed description of the investigative procedures followed in addressing the requirements of this section and which includes the results of all tests or monitoring performed. This report must be filed with the agency not later than 45 days after the first observation of the suspected release or another schedule approved or required by the agency. The owner or operator shall include with this report a statement which has been signed by the owner or operator certifying that the requirements of this section have been met.

Source Note: The provisions of this §334.74 adopted to be effective September 29, 1989, 14 TexReg 4714; amended to be effective November 23, 2000, 25 TexReg 11442; amended to be effective May 31, 2018, 43 TexReg 3390