(1) Any bonds issued under this part 5 may be refunded, without an election, pursuant to a resolution adopted by the board in the manner provided in this part 5 for the issuance of other securities, subject to any contractual limitations, to refund, pay, or discharge all or any part of the district's outstanding bonds, including any interest thereon in arrears or about to become due, or for the purpose of reducing interest costs or effecting other economies or of modifying or eliminating restrictive contractual limitations appertaining to the issuance of additional bonds for any sewage disposal system or project.

(2) Any bonds issued for refunding purposes may either be delivered in exchange for the outstanding bonds authorized to be refunded or may be sold as provided in this part 5 for the sale of other bonds.

(3) No bonds may be refunded under this part 5 unless they either mature or are callable for prior redemption under their terms within ten years from the date of issuance of the refunding bonds, or unless the holders thereof voluntarily surrender them for exchange or payment. No maturity of any bonds refunded may be extended over fifteen years. The rate of interest on such refunding bonds shall be determined by the board. The principal amount of the refunding bonds may exceed the principal amount of the refunded bonds if the aggregate principal and interest costs of the refunding bonds do not exceed such unaccrued costs of the bonds refunded.

(4) The proceeds of refunding bonds shall either be immediately applied to the retirement of the bonds to be refunded or be placed in escrow to be applied to the payment of the bonds upon their presentation therefor. Any escrowed proceeds, pending such use, may be invested or reinvested in securities meeting the investment requirements established in part 6 of article 75 of title 24, C.R.S. Such escrowed proceeds and investments, together with any interest to be derived from any such investment, shall be in an amount at all times sufficient to pay the bonds refunded as they become due at their respective maturities or due at prior redemption dates as to principal, interest, any prior redemption premium due, and any charges of the escrow agent payable therefrom.

(5) Refunding revenue bonds may be made payable from any revenues derived from the operation of any sewage disposal system or project, or any other source, notwithstanding that the pledge of such revenues for the payment of the outstanding bonds issued by the district which are to be refunded is thereby modified.

(6) Bonds for refunding and bonds for any other purpose authorized in this part 5 may be issued separately or issued in combination in one series or more.

(7) Except as in this section specifically provided or necessarily implied, the relevant provisions in this part 5 pertaining to bonds shall be equally applicable in the authorization and issuance of refunding bonds, including their terms and security, the bond resolution, trust indenture, taxes, and service charges, and other aspects of the bonds.

(8) The determination of the board that the limitations under this part 5 imposed upon the issuance of refunding bonds have been met shall be conclusive in the absence of fraud or arbitrary and gross abuse of discretion.