Tex. Loc. Gov't Code § 152.906

In a county with a population of 190,000 or more, the commissioners court may provide for each county employee or classification of county employee, including, but not limited to, deputy constables, longevity pay, in addition to regular compensation, of $5 a month, or any other amount determined by the commissioners court, for each year of service in the county, up to and including 30 years.