(a) Applicability. An underground storage tank (UST) system shall be considered to be temporarily out of service, regardless of whether or not regulated substances remain in the UST system, when the following conditions apply.      
        (1) The normal operation and use of the UST system is deliberately, but temporarily, discontinued for any reason.       
        (2) The infrequent use of the UST system cannot be adequately justified as part of its purpose.       
        (3) The operation, maintenance, and/or release detection procedures are determined to be inadequate or otherwise inconsistent with the monitoring procedures normally associated with in-service systems of similar type and purpose.       
      (b) All UST systems. Regardless of whether or not regulated substances remain in the UST system, the owner or operator shall assure that the UST system is maintained in compliance with the following requirements for the balance of time that the UST system remains temporarily out of service.      
        (1) All vent lines shall be kept open and functioning.       
        (2) All other piping, pumps, manways, tank access points (e.g., fill risers, automatic tank gauging risers, Stage I vapor recovery risers) and ancillary equipment shall be capped, plugged, locked, and/or otherwise secured to prevent access, tampering, or vandalism by unauthorized persons.       
        (3) The UST system shall be adequately protected from corrosion in accordance with the applicable requirements of §334.49 of this title (relating to Corrosion Protection).       
        (4) Testing and inspections. Spill and overfill operation and maintenance testing and walkthrough inspections (as listed in §334.48(g) and (h) of this title (relating to General Operating and Management Requirements)) are not required on temporarily out of service UST systems.       
      (c) Protected and monitored systems. Any UST system may remain out of service indefinitely so long as the following requirements are met during the period that the UST system remains temporarily out of service.      
        (1) Unless the UST system has been emptied of all regulated substances (as described under subsection (d) of this section) at the time it is temporarily removed from service, the UST system shall be monitored for releases in accordance with the applicable requirements of §334.50 of this title (relating to Release Detection).       
        (2) Returning UST system to service.                  (A) When a protected and empty UST system that has been temporarily out of service for longer than six months is placed back into service, the owner or operator shall ensure the integrity of the system by the performance of tank tightness and piping tightness tests that meet the requirements of §334.50(d)(1)(A) of this title, and as applicable, §334.50(b)(2)(A)(ii)(I) or (B)(i)(I) of this title, prior to bringing the system back into operation;                   (B) When either a protected and monitored or a protected and empty UST system is placed back into service, the owner or operator shall also ensure that the UST system either is in compliance or is brought into compliance with all applicable release detection, and spill and overfill prevention requirements of §334.50 of this title and §334.51 of this title (relating to Spill and Overfill Prevention and Control); and                   (C) Before any UST system is returned to service under this subsection, the owner or operator must first submit a construction notification form as specified in §334.6(b) of this title (relating to Construction Notification for Underground Storage Tanks (USTs) and UST Systems).         
      (d) Empty system.      
        (1) For the purposes of this section only, and specifically for the purpose of exempting certain UST systems (when temporarily out of service) the following requirements shall not apply as long as a UST system is empty:                  (A) release detection (as listed in §334.50 of this title); and                   (B) release detection operation and maintenance testing and inspections (as listed in §334.48(e)(1) of this title).         
        (2) A UST system shall be considered empty when all of the following provisions have been met:                  (A) all regulated substances have been removed as completely as possible by the use of commonly-employed and accepted industry procedures;                   (B) any residue from stored regulated substances which remains in the system (after the completion of the substance removal procedures under subparagraph (A) of this paragraph) shall not exceed a depth of 2.5 centimeters at the deepest point and shall not exceed 0.3% by weight of the system at full capacity; and                   (C) the volume or concentration of regulated substances remaining in the system would not pose an unreasonable risk to human health and safety or to the environment if a release occurs during the period when the system is temporarily out of service.         
      (e) Other requirements.      
        (1) Releases. If a release of a regulated substance is suspected or confirmed, the owner or operator of a UST system which is temporarily out of service shall comply with all release reporting, investigation, and corrective action requirements in Subchapter D of this chapter (relating to Release Reporting and Corrective Action).       
        (2) Registration. At the time a UST system is temporarily taken out of service and at the time a UST system is brought back into service, the owner shall comply with the applicable tank registration requirements in §334.7 of this title (relating to Registration for Underground Storage Tanks (USTs) and UST Systems).       
        (3) Fees. A UST which is temporarily out of service in accordance with this section shall remain subject to the agency's UST fees in Subchapter B of this chapter (relating to Underground Storage Tank Fees).       
        (4) Recordkeeping for temporary removal from service.                  (A) Owners and operators shall maintain records adequate to demonstrate compliance with the requirements in this section, in accordance with §334.10(b) of this title (relating to Reporting and Recordkeeping).                   (B) At a minimum, the following records shall be maintained for at least five years after the UST system is temporarily removed from service:                      (i) date that the UST system was temporarily removed from service;                       (ii) name, address, and telephone number of the person who prepared the UST system for the period of non-use;                       (iii) documentation of the procedures used to prepare and empty the UST system;                       (iv) copies of all documentation relative to any requests and approvals of extensions of time;                       (v) name, address, and telephone number of the person who conducted the tank and piping tightness tests, prior to returning the UST system to service;                       (vi) results of any tank and piping tightness tests; and                       (vii) date that the UST system was returned to service.           
        (5) Financial assurance requirements for tanks temporarily removed from service. Note that §37.885 of this title (relating to Release from the Requirements) addresses release from financial assurance requirements. To be considered properly temporarily removed from service for release from financial assurance requirements in §37.885 of this title, owners and operators shall:                  (A) empty the UST system in accordance with subsection (d) of this section; and                   (B) perform a site check and any necessary corrective actions in accordance with the requirements of §334.74 of this title (relating to Release Investigation and Confirmation Steps).         
     Source Note:        The provisions of this §334.54 adopted to be effective September 29, 1989, 14 TexReg 4714; amended to be effective November 23, 2000, 25 TexReg 11442; amended to be effective July 12, 2001, 26 TexReg 5031; amended to be effective April 2, 2002, 27 TexReg 2522; amended to be effective October 30, 2008, 33 TexReg 8790; amended to be effective May 31, 2018, 43 TexReg 3390