; or (IV) other dedicated revenue sources that also secure the senior project obligations; and (ii) include a coverage requirement or similar security feature supporting the project obligations; and (B) may have a lien on revenues described in subparagraph (A), subject to any lien securing project obligations. (4) Interest rate The interest rate on a secured loan under this section shall be not less than the yield on United States Treasury securities of a similar maturity to the maturity of the secured loan on the date of execution of the loan agreement. (5) Maturity date The final maturity date of the secured loan shall be the lesser of— (A) 35 years after the date of substantial completion of the project; and (B) if the useful life of the infrastructure for the provision of broadband service being financed is of a lesser period, the useful life of the infrastructure. (6) Nonsubordination (A) In general Except as provided in subparagraph (B), the secured loan shall not be subordinated to the claims of any holder of project obligations in the event of bankruptcy, insolvency, or liquidation of the obligor. (B) Preexisting indenture (i) In general The Assistant Secretary shall waive the requirement under subparagraph (A) for a public agency borrower that is financing ongoing capital programs and has outstanding senior bonds under a preexisting indenture, if— (I) the secured loan— (aa) is rated in the A category or higher; or (bb) in the case of a small project, meets an alternative standard that the Assistant Secretary shall establish under section 6 for purposes of this subclause; (II) the secured loan is secured and payable from pledged revenues not affected by project performance, such as a tax-backed revenue pledge or a system-backed pledge of project revenues