020-17 Wyo. Code R. § 17-32
(a) UST systems permanently closed after December 22, 1988 and AST systems permanently closed after the date of these regulations, shall comply with the state requirements for closure by either removing the storage tank system from the ground or permanently closing it in place in accordance with Section 31 and 33.
(b) When directed by the administrator, the owner and/or operator of a storage tank system or an owner of a site upon which such a system was located that was permanently closed before the effective date of these regulations shall accomplish a Minimum Site Assessment in accordance with Section 29. When directed by the administrator, abandoned storage tank systems shall be permanently closed in accordance with Sections 31 and 33. The administrator may take action under this section if the department determines that releases from the storage tank system may pose a current or potential threat to human health and/or the environment. Owners and/or operators of UST systems permanently closed before December 22, 1988, shall have complied with the practice of API Bulletin No. 1604, Recommended Practice for Abandonment or Removal of Underground Tanks.
020-17 Wyo. Code R. § 17-32