(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.