(2) Such annual levy shall not exceed one-tenth of one percent. The proceeds thereof shall be used only in the purchase on the open market of bonds of the port, at such prices, as the board determines.
(3) All funds collected from such levy shall be placed in a separate fund, designated the bond sinking fund, and shall be used exclusively for the purposes provided by this section as long as the principal of any bond of the port remains outstanding or unpaid. After the principal of all bonds of the port has been paid, the balance remaining in such fund may be transferred to any other fund as the board may direct. [Amended by 1971 c.728 §85]