Rural Regulation: Non-MS4 Stormwater Management

Rural stormwater management plans are growing in popularity. The proper development and maintenance of BMPs is important even in areas away from intense development, as runoff can still negatively affect water quality and surrounding environments. There are physical and regulatory differences to managing stormwater in rural vs. urban areas, and knowing how localities can use their ordinances to mandate runoff requirements outside of MS4s can help ensure your business stays compliant.

MS4s - Small Area, High Impact

According to the EPA, Municipal Separate Storm Sewer Systems (MS4s) cover only 4% of the land area in the US, but support over 80% of the population. These conveyance systems owned by a state or city help manage runoff as required by the National Pollution Discharge Elimination System (NPDES) through the stormwater management program. The program was implemented in two phases, initially applying to larger cities and then extending to cover smaller cities are other areas with high population densities. So what exactly is required of an MS4 program, and how does it impact stormwater?

If a municipality has an MS4, they also have a Stormwater Management Program (SWMP). This NPDES requirement has specific guidelines for the maximum amount of different pollutants that are allowed to enter waterways, and establishing regulations for managing runoff from development and redevelopment sites as well as post construction requirements. Each SWMP details the best management practices and specific control practices that will be used to meet the regulations, which they themselves also have to meet the water quality and technology standards of the federal Clean Water Act (which brought about the NPDES).

Yet while they cover our highest population areas, the vast majority of land area is not regulated by MS4s. In smaller towns where only part of the municipality is required to have an MS4, it’s common to see the regulations extended to the whole area to give consistency to enforcement. For jurisdictions where no area meets the requirements to establish a SWMP, as long as water quality standards are met under the CWA, no stormwater management is required.

Out of Bounds

The EPA and the Center for Watershed Protection use impervious area percentage to distinguish between levels of development, where “rural” is 0-10% impervious, “suburban” is 10-25%, “urban” is 25-60%, and “ultra-urban” is greater than 60%. The higher the percent imperviousness, the greater the area blocked for stormwater to infiltrate back into the soil or make its way to nearby surface water. This is the reasoning behind stricter stormwater regulations in urban areas, however there are still environmental and public health impacts from rural runoff. Wherever there’s rain there’ll be runoff, whether its falling on a city or a small town.

If you are in an area not considered urbanized under the census, are disturbing less than an acre of land, or are developing for agricultural practices (no matter how large), you are exempt from putting a stormwater plan in place under the NPDES. While not federally regulated, these practices can contribute runoff high in sediment, pesticides, and other contaminants.

Whether its urban or rural, fighting stormwater pollution is done by reducing the amount of pollutants in the water, and reducing the amount of runoff in the first place. Urban areas have more to worry about when it comes to infiltration and directing the water, and have a different set of pollutants of concern as well. Runoff from urban streets and parking lots is more likely to contain gasoline and oil than fertilizers. Rural areas are more concerned with sediment control, land use practices exempt from regulations, and sources of contamination that are often harder to locate. Pollutants could be heavy metals from the roof of an old shed, or nitrates accumulating from agricultural runoff. Because of the significant potential for pollution and the lack of federal requirements, many municipalities have starting moving towards creating their own ordinances for land not covered by an MS4.

Self-Imposed Stormwater Management

Knowing that the lack of MS4 coverage doesn’t change the impacts of stormwater runoff, and having urban regulations as a guideline, smaller counties and towns are implementing their own stormwater programs. Cowlitz County in Washington State addressed their concerns by developing their own stormwater management program, and stated that:

“Unmitigated development is detrimental to the safety, welfare, and health of the citizens residing adjacent to and downstream from said development. Unmitigated development has the potential to substantially alter the natural drainage characteristics of drainage courses such that the water is diverted and thereby affects adjacent property and property owners’ rights. Substantial unmitigated development in drainage courses is also detrimental to the environment of Cowlitz County.”

Rural stormwater management impacts residents, developers, property owners, the local environment, as well as people and ecosystems downstream. With all these stakeholders invested, more and more municipalities are moving towards self-imposed regulations. In rural Ontario, the Healthy Lake Huron project designed to improve water quality in the lake through runoff management was developed through the “collaborative effort of ministries, local conservation agencies, public health, county and local government, municipalities, community groups, and landowners along Lake Huron’s southeast shores.”

Urbanization affects more than just cities, and the EPA recognizes that “urbanization causes extensive changes to the land surface beyond its immediate borders, particularly in ostensibly rural regions, through alterations by agriculture and forestry that support the urban population.” This rural development increases the need for runoff management, and makes maintaining stormwater management systems away from cities even more important. While agriculture remains exempt, it is important to check local regulations for residential, commercial, and industrial during and post construction stormwater management as new policies with stricter requires are springing up across the country. Checking state or federal requirements works well for areas covered by an MS4, but for lower population areas it’s imperative to check local compliance. Many county ordinances are included in our Laws and Regulations page, and are a good reference for state and local requirements. If you’d like to learn more or have questions about your site’s compliance don’t hesitate to reach out to us!