(a) A bond issued under this subchapter, including a refunding bond, that is 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 the deed of trust or mortgage lien on the property, may:(1) provide for the security of the bonds and the preservation of the trust estate in the manner 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 2007, 80th Leg., R.S., Ch. 920 (H.B. 3166), Sec. 1.06, eff. April 1, 2009.