Tex. Tax Code § 311.007

(a) Subject to the limitations provided by Section 311.006, if applicable, the boundaries of an existing reinvestment zone may be reduced or enlarged by ordinance or resolution of the governing body of the municipality or by order or resolution of the governing body of the county that created the zone.

(b) The governing body of the municipality or county may enlarge an existing reinvestment zone to include an area described in a petition requesting that the area be included in the zone if the petition is submitted to the governing body of the municipality or county by the owners of property constituting at least 50 percent of the appraised value of the property in the area according to the most recent certified appraisal roll for the county in which the area is located. The composition of the board of directors of the zone continues to be governed by Section 311.009(a) or (b), whichever applied to the zone immediately before the enlargement of the zone, except that the membership of the board must conform to the requirements of the applicable subsection of Section 311.009 as applied to the zone after its enlargement. The provision of Section 311.006(b) relating to the amount of property used for residential purposes that may be included in the zone does not apply to the enlargement of a zone under this subsection.

(c) The governing body of the municipality or county that designated a reinvestment zone by ordinance or resolution or by order or resolution, respectively, may extend the term of all or a portion of the zone after notice and hearing in the manner provided for the designation of the zone. A taxing unit other than the municipality or county that designated the zone is not required to participate in the zone or portion of the zone for the extended term unless the taxing unit enters into a written agreement to do so.