Any city combining its airport with any harbor improvement plan into a single system as provided in Section 6-21-40 may secure such bonds as may be issued therefor by pledges of the revenues from such combined system, and it may additionally secure such bonds by pledges of any of the revenues that might from time to time become receivable by said city from any other source or sources except the proceeds of ad valorem taxes. Bonds issued pursuant to this chapter for such purposes may, in the discretion of the governing body of said city, be primarily secured by a pledge of the revenues from such system as provided by Section 6-21-440.
S.C. Code § 6-21-240