EPA requires stormwater permits for discharges from an MS4 serving a population of 100,000 or more. EPA also defined MS4s to include road systems owned by states that discharge to water of the United States. There are currently three large MS4s in Nevada with separate MS4 Permits. They are:
- Las Vegas Valley - Permit NV0021911 that authorizes stormwater discharges into receiving waters of the United States within the Cities of Henderson, Las Vegas and North Las Vegas, and Clark County that are located within the Las Vegas Valley.
- Truckee Meadows - Permit NVS000001 that authorizes stormwater discharges into receiving water of the United States within the Cities of Reno and Sparks, and Washoe County that are located within the Truckee Meadows.
- Nevada Department of Transportation (NDOT) - Permit NV0023329 that covers state and interstate highways and their right-of-ways within the jurisdictional boundary of NDOT served by, or otherwise contributing to discharges into receiving waters of the United States from MS4s owned or operated by NDOT.