Or. Rev. Stat. § 287A.325
(1) The Legislative Assembly finds that:
(4) A public body may enter into rate covenants that obligate the public body to periodically set rates and charges:
(d) In accordance with a formula established in the operative document governing revenue bonds or other borrowings. The formula may provide for rates and charges to be determined by reference to factors including, but not limited to:
[2007 c.783 §51]