‚ÄčMunicipal Separate Storm Sewer Systems (MS4)


The Louisiana Department of Transportation and Development's Municipal Separate Storm Sewer System (MS4) Web-site is published as a control measure to address the requirements of its statewide MS4 Phase II permit. This permit was issued to DOTD by the Louisiana Department of Environmental Quality. Compliance with this permit is the responsibility of DOTD. The LA DEQ and the U.S. EPA are the regulatory agencies responsible for enforcing this permit. Compliance with this MS4 permit is achieved through a Departmental Storm Water program which is managed by DOTD's Environmental Evaluation Unit. This web-site is designed to assist in the national effort to educate the public to a better understanding of the municipal storm sewer system initiative for improving the quality of the nation's surface waters. Additionally and more specifically, this web-site serves as a contact between DOTD and the public, allowing individuals a means to report illicit discharges occurring within DOTD's system of highways. To the extent the public follows best management practices and reports spills or illicit discharges, DOTD will have an increased ability to maintain compliance with the conditions of its MS4 permit.

In 1987, Congress amended the Clean Water Act (CWA) to require a two phase implementation of a comprehensive national strategy for addressing storm water discharges. Phase I requires operators of medium and large municipal storm sewer systems, those that generally serve a population of 100,000 or greater, to obtain NPDES permits and implement a storm water management program. Phase II of the amended CWA regulates small MS4s. Certain operators of small municipal storm sewer systems, mostly those located in urbanized areas, are required to implement practices to control polluted storm water runoff from the jurisdiction serviced by the municipal storm sewer system. The operator must design its storm water management program to satisfy applicable CWA water quality requirements. Each program must include the development and implementation of best management practices (BMPs) and measurable goals for six minimum control measures. As the Louisiana Department of Transportation and Development strives to improve mobility across Louisiana, it is the Department's responsibility to plan, design, construct, and maintain transportation facilities throughout the state. It is the goal of the LaDOTD to perform each of these duties in an environmentally-sensitive manner.

The LaDOTD was issued a statewide MS4 Phase II permit in 2003.

What Is A MS4 ?

The definition of a municipal separate storm sewer system (MS4) is often complex and misunderstood. The term MS4 is a broad term that does not only refer to municipally owned storm sewer systems. It can also include systems owned by State departments of transportation, universities, local sewer districts, hospitals, military bases, and prisons. An MS4 is not only a system of underground pipes, but can include roads with drainage systems, gutters, and ditches. The regulatory definition of an MS4 is provided below.

According to 40 CFR 122.26(b)(8), "municipal separate storm sewer means a convenance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains:

A conveyance or system of conveyances (including roads with drainage systems, municipal streets, catch basins, curbs, gutters, ditches, man-made channels, or storm drains):

  1. Owned or operated by a state, city, town, borough, county, parish, district, association, or other public body (created by or pursuant to state law) ... including special districts under state law such as a sewer district sewer district, flood control district or drainage district, or similar entity, or an Indian tribe or an authorized Indian tribal organization, or a designated and approved management agency under section 208 of the Clean Water Act that discharges into waters of the United States;
  2. Designed or used for collecting or conveying stormwater;
  3. Which is not a combined sewer; and
  4. Which is not part of a publicly owned treatment works (POTW) as defined at 40 CFR 122.2."