Mo. Rev. Stat. § 393.745: Refunding bonds may be issued.

Any commission governed by the provisions of sections 393.700 to 393.770 having issued bonds under sections 393.700 to 393.770 may from time to time as authorized by resolution of the commission or by resolution of its executive committee if the board has delegated such authority issue refunding bonds for the purpose of refunding, extending and unifying the whole or any part of its valid outstanding indebtedness.