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Water: Stormwater

Road-Related MS4s

Challenges to Stormwater Management

Road and highway systems, while a primary method in how we get from place to place, can transport more than cars, trucks, and buses. Impervious surfaces can quickly convey polluted runoff during wet weather events to nearby waterways. Road surfaces can carry both land-adjacent and road-vehicle pollutants including heavy metals from tires, brakes, and engine wear, and hydrocarbons from lubricating fluids. If these pollutants are not properly controlled they can impair waters causing them to no longer support the water's designated uses and biotic communities.

Transportation authorities are responsible for maintaining stormwater systems along streets, roads, and highways by managing the quality and quantity of stormwater discharging to our nation's waters via those systems. Transportation MS4 management differs in some ways from traditional MS4s (e.g., cities and towns). Some of the differences include:

  • Linear transportation systems often stretch for many miles, and cross numerous waterways, watersheds, and jurisdictions.
  • Transportation storm conveyance systems often discharge stormwater and associated pollutants that originate outside of the transportation right-of-way.
  • Transportation systems often serve a literally transient population.
  • There is little to no enforcement authority to implement ordinances.

Image of high density traffic

Transportation Stormwater Needs

An integrated approach is needed to address these challenges and strengthen stormwater management programs. This site is geared toward state, county, and local transportation authorities to coordinate transportation-specific stormwater information including MS4 permit language, outreach materials, good practices, retrofit case studies, better designs for stormwater controls, and links to transportation stormwater programs, agencies and organizations.

Stormwater Regulations

Under the National Pollutant Discharge Elimination System (NPDES), transportation MS4s are required to manage their stormwater discharges through a comprehensive stormwater program. EPA has authorized most states to administer the NPDES program.

Other Information


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