(a) In accordance with the findings, the board may impose an assessment against all the facilities in the district or any portion of the facilities in the district, and may impose an assessment against fewer facilities than those proposed for assessment in the hearing notice.
(b) Except as provided by Subsection (c), the facilities to be assessed may not include a facility that is not in the district at the time of the hearing unless there is an additional hearing preceded by the required notice.
(c) The owner of a facility described by Subsection (b) may waive the right to notice and an assessment hearing and may agree to the imposition and payment of assessments at an agreed rate for the facility.