Sec. 286.013.  VALIDITY OF ASSESSMENT.  An assessment related to the cost of an improvement that is to be constructed is not valid unless the commissioners court:
(1)  makes or causes to be made an estimate of the cost of the improvement;  and
(2)  includes the estimate in a published or mailed notice required by Section 286.007.
Acts 1995, 74th Leg., ch. 165, Sec. 1, eff. Sept. 1, 1995.