Lewisville, TX Environmental Rules: Stormwater Management (2026)

City Code Chapter 16, Article VIII governs discharges into Lewisville's municipal separate storm sewer system (MS4). Section 16-375 bars introducing anything into the MS4 that isn't entirely stormwater, except the narrow list of allowed non-stormwater discharges in Section 16-376 (things like dechlorinated pool water, uncontaminated irrigation runoff, and emergency firefighting flows). The article separately prohibits discharging waste concrete into or near the MS4, intentionally dumping yard waste such as grass clippings or tree branches into a drain, and any harmful quantity of sediment, silt, or soil beyond what onsite erosion controls could retain. Illicit physical connections to the MS4 are banned outright under Section 16-377, and Section 16-378 requires an NPDES or TPDES permit before discharging stormwater tied to commercial, industrial, or construction activity.

Construction sites face the most detailed obligations. Section 16-379 requires every operator of a large or small construction activity to develop, implement, and maintain a stormwater pollution prevention plan (SWPPP) built on the North Central Texas Council of Governments' integrated Stormwater Management (iSWM) manuals, and to submit the signed SWPPP to the control authority alongside any development or building permit application. The SWPPP must be completed before construction starts and kept onsite until final stabilization, with site inspections required at least every 14 calendar days and within 24 hours after a storm of 0.5 inches or more. Concrete truck washout water can never be discharged directly to the MS4 or state water; it must go to a berm, pit, or tank designed to prevent runoff. If the control authority finds a SWPPP or best management practice deficient during an inspection, the operator has seven calendar days to start repairs, and the city can withhold a building permit, certificate of occupancy, or final acceptance until the site complies. The director of public services and the director's authorized representatives administer and enforce the entire article under Section 16-374.