Section 280.90 - Applicability(a) This subpart applies to owners and operators of all petroleum underground storage tank (UST) systems except as otherwise provided in this section.(b) Owners and operators of petroleum UST systems are subject to these requirements in accordance with § 280.91 .(c) State and Federal government entities whose debts and liabilities are the debts and liabilities of a state or the United States are exempt from the requirements of this subpart.(d) The requirements of this subpart do not apply to owners and operators of any UST system described in § 280.10(b), (c)(1), (c)(3), or (c)(4) .(e) If the owner and operator of a petroleum underground storage tank are separate persons, only one person is required to demonstrate financial responsibility; however, both parties are liable in event of noncompliance.