In this case two principal issues are (1) whether the city's public-works director acted without authority in calculating impervious cover for imposing a drainage utility-district fee to pay for the effects of runoff and (2) whether the director acted without authority in determining which properties "benefitted" from the city's drainage system. Houston Belt & Terminal Railway and other railroads sued over drainage-utility assessments based on the public-works director's determination of how much impervious cover existed on their properties. They argue the basis for those assessments were aerial maps showing green and brown areas – brown assumed to be impervious cover – instead of digital-map data, as they contend the city ordinance requires, from tax plats, assessments and "other similar reliable data." By using the aerial maps, the director determined almost all the railroads' property was impervious. The trial court granted the city's jurisdictional plea to dismiss the challenge. The appeals court reversed in part.