Cameron County, TX Environmental Rules: Stormwater Management (2026)

7 of the county's Subdivision Rules and Regulations governs every drainage system built in an unincorporated subdivision. A, storm water runoff from lots must be conveyed to streets or drainage courses as directly as possible, and runoff from streets must reach a defined off-site drainage course or a County-approved on-site basin. B places the design and construction burden, including acquiring rights-of-way and easements, on the subdivision's developer, using a professional engineer's design. C requires a Comprehensive Drainage Plan, an engineering report signed and sealed by the engineer and submitted to the County Engineer for review and approval, confirming the final outfall can carry the subdivision's flows combined with the rest of the drainage basin.

D sets storm-return-period targets by street class: minor streets must contain a 5-year storm within the gutter or borrow ditch (4-inch maximum pavement depth) and hold a 25-year storm within the right-of-way; collector streets must contain a 10-year storm in the gutter and a 50-year storm within the right-of-way; arterial culverts must carry a 25-year storm. The same subsection requires compliance with the EPA's National Pollution Discharge Elimination System (NPDES) rules. E requires major conveyances such as ditches and detention basins to carry a 25-year storm without exceeding 3 feet per second on bare ground or 7 feet per second on vegetated ground. G extends the detention requirement to every commercial lot.