(a) District bonds, including refunding bonds, that are not payable wholly from ad valorem taxes may be additionally secured by a trust indenture. The trustee may be a bank with trust powers located inside or outside the state.(b) A trust indenture, regardless of the existence of a deed of trust or mortgage lien on property, may:(1) provide for the security of the bonds and the preservation of the trust estate as prescribed by the board;(2) provide for amendment or modification of the trust indenture;(3) provide for the issuance of bonds to replace lost or mutilated bonds;(4) condition the right to spend district money or sell district property on the approval of a licensed engineer selected as provided by the trust indenture; and(5) provide for the investment of district money. Added by Acts 2015, 84th Leg., R.S., Ch. 855 (S.B. 1162), Sec. 1.07, eff. April 1, 2017.