Tex. Loc. Gov't Code § 375.111

In addition to the powers provided by Subchapter E, the board of a district may undertake improvement projects and services that confer a special benefit on all or a definable part of the district. The board may levy and collect special assessments on property in that area, based on the benefit conferred by the improvement project or services, to pay all or part of the cost of the project and services. If the board determines that there is a benefit to the district, the district may provide improvements and services to an area outside the boundaries of the district.