As used in Sections 13273, 13273.1, and 13273.2, “operator” means a person who operates or manages, or who has operated or managed, the solid waste disposal site. If the operator of the solid waste disposal site no longer exists, or is unable, as determined by the regional board, to comply with the requirements of Section 13273, 13273.1, or 13273.2, “operator” means any person who owns or who has owned the solid waste disposal site.