(a) Any owner or operator who intends to change the status of an underground storage tank (UST) system from regulated to exempt or excluded status must determine whether the tank(s) size (if applicable) and the current and anticipated use of the UST system will allow reclassification to either exempt status as specified in §334.3 of this title (relating to Exemptions for Underground Storage Tanks (USTs) and UST Systems), or to excluded status as specified in §334.4 of this title (relating to Exclusions for Underground Storage Tanks (USTs) and UST Systems).     
      (b) As part of the required procedure for the change in status of any UST system from regulated to exempt or excluded status, the owner or operator shall determine whether or not any prior release of a stored regulated substance has occurred from the system.      
        (1) This determination shall be made by visual inspection of the area in and immediately surrounding the excavation zone for any above-ground releases and for any exposed below-ground releases, and by using one or both of the following methods or procedures:                  (A) the continual operation (through the time that the stored regulated substances are removed from the UST system) of one or more of the external release monitoring and detection methods operated in accordance with §334.50(d)(5) - (8) of this title (relating to Release Detection); or                   (B) the performance of a comprehensive site assessment in accordance with the requirements of subsection (c) of this section.         
        (2) Any methods or procedures used to make this determination shall be capable of detecting any prior release of stored regulated substances from any portion of the UST system. Upon completion of this determination, the owner or operator shall:                  (A) report any confirmed or suspected releases to the agency and comply with all applicable release investigation and corrective action requirements, as prescribed in Subchapter D of this chapter (relating to Release Reporting and Corrective Action);                   (B) prepare or assemble the detailed written records of this determination, which shall include the methods, procedures, results, names, addresses, and telephone numbers of the persons involved in conducting this determination. These records shall be maintained in accordance with the applicable provisions in subsection (d) of this section, and a copy of these records shall be filed with the agency in conjunction with the applicable tank registration requirements of §334.7 of this title (relating to Registration for Underground Storage Tanks (USTs) and UST Systems).         
      (c) Site assessment.      
        (1) A comprehensive site assessment meeting the requirements of this subsection shall be performed by the owner or operator of a UST system in the following situations to determine whether or not a release has occurred:                  (A) when the site assessment is selected as the method to achieve compliance with the release determination requirements of subsection (b) of this section for a UST which is changed from regulated to exempt or excluded status on or after the effective date of this subchapter;                   (B) when the agency determines that a comprehensive site assessment is necessary at any site or facility where a release or suspected release may pose a current or potential threat to human health or safety or the environment.         
        (2) The site assessment shall be conducted by qualified personnel possessing the appropriate skills, experience, and competence to perform the assessment in accordance with recognized industry practices and the provisions of this section and shall be supervised by a person who is currently licensed by the Texas Commission on Environmental Quality (TCEQ) as a UST installer or on-site supervisor or currently registered with the TCEQ as a corrective action project manager.       
        (3) Any procedures used for the site assessment must be capable of measuring for the presence of a release from any part of the UST system and, at a minimum, must include measurements for releases at locations where contamination is most likely to be present at the site.       
        (4) The owner or operator shall assure that in selecting the sampling or measurement methods, the sample types, and the sampling or measurement locations, the persons conducting the assessment shall take into consideration the following factors to ensure that the presence of any released regulated substances is detected and quantified:                  (A) the nature and composition of the stored regulated substance;                   (B) the type and characteristics of the backfill material and surrounding soils;                   (C) the presence of groundwater, and its depth with relation to the UST system and the surface of the ground; and                   (D) any other factors that may affect the reliability or effectiveness of the site assessment procedures or techniques.         
        (5) One or more of the following methods may be used for conducting the site assessment and release determination required under this section, provided that such methods are in compliance with the performance standards in paragraphs (2) - (4) of this subsection:                  (A) collection and analysis of soil samples secured from unsaturated sections of the UST system excavation zone and surrounding soils, where such samples shall be analyzed for major constituents and/or indicator parameters of the stored regulated substance(s);                   (B) collection and analysis of groundwater samples secured from the UST system excavation zone and surrounding area, where such samples shall be analyzed for all major constituents or indicator parameters of the stored regulated substance(s); and/or                   (C) any other site assessment or release determination method or procedure which has been reviewed and determined by the agency to detect prior releases of the stored regulated substance(s) in a manner that is no less protective of human health and the environment than the methods described in subparagraphs (A) and (B) of this paragraph, as provided under §334.43 of this title (relating to Variances and Alternative Procedures).                   (D) The owner or operator must report any suspected or confirmed releases indicated by the site assessment to the agency and comply with all applicable release investigation and corrective action requirements, as prescribed in Subchapter D of this chapter.         
      (d) Records for change to exempt or excluded status.      
        (1) Owners and operators shall maintain records adequate to demonstrate compliance with the requirements of this section, in accordance with §334.10(b) of this title (relating to Reporting and Recordkeeping).       
        (2) At minimum, records of the release determination or site assessment, in accordance with the requirements in subsection (b)(2)(A)(ii) of this section shall be maintained for as long as any UST remains in service at the facility, or for five years after the UST system is changed from regulated to exempt or excluded status, whichever is longer.       
     Source Note:        The provisions of this §334.56 adopted to be effective November 23, 2000, 25 TexReg 11442; amended to be effective November 18, 2004, 29 TexReg 10532