Stormwater BMPs, Not Just a Pretty Space

Brad Lee, Associate Extension Specialist

Stormwater can be defined as any surface water runoff.  Essentially this is the quantity of water that is equal to:

 Rainfall – (soil infiltration + evaporation) = stormwater.

In agricultural areas there are several incentive programs to encourage landowners to install/adopt BMPs to reduce risk of stormwater runoff entering nearby waterways.  Agricultural producers have a good understanding about how to minimize runoff to improve water quality.  However, in urban communities, a lower percentage of the population understands how activities around their home and in their daily lives negatively impact water quality.

In densely populated urban areas there is a much lower chance for rain water to infiltrate. This is due to the abundant impervious surfaces (roads, sidewalks, parking lots, buildings, etc.) common in cities and towns.  When rain water moves across these impervious surfaces it picks up contaminants and moves these contaminants through a conveyance system such as piping or ditches.  In communities with a combined sewer system, stormwater will be conveyed to the sewage treatment facility.  In communities with a separate conveyance system, stormwater is not treated and is discharged directly to a nearby waterbody.

Communities with combined systems are being addressed by EPA’s Combined Sewer Overflow (CSO) Control Policy, which encourages communities to separate their stormwater conveyance system from the sanitary sewer system.  Older combined storm and sewer treatment systems are outdated and result in a Combined Sewer Overflow (CSO) several times a year which discharges raw sewage to a stream or river.  Presently, there are 17 Kentucky communities with permitted CSO outfalls.  (There are over 750 permitted CSOs across the US.) These are being phased out nationwide as EPA encourage/requires communities to separate their stormwater and sewage conveyance and treatment systems.

Communities that have a Municipal Separate Storm Sewer Systems (MS4) often do not have a treatment process and discharge stormwater directly into a waterway.  The EPA regulates these MS4s (population over 10,000) through NPDES (National Pollution Discharge Elimination System) permits.  These regulated communities are charged with managing their stormwater runoff in a responsible manner that minimizes negative impacts to Kentucky streams.  Keep in mind that both CSO and MS4 management entities in your communities are interested in encouraging rainwater infiltration and minimizing stormwater runoff.

Most of the MS4s have a permit manager that has multiple responsibilities and cannot focus 100% of their time on the MS4 permit requirements (e.g. city engineer). The MS4 permit manager administers the community permit for the municipality executive director or county judge/executive and files annual reports to the DOW, which reports to the EPA.  Other communities pull from local resources to manage their stormwater programs.  At a minimum all MS4s are required to meet six Minimum Control Measures (MCMs):

  1. Public Education and Outreach
  2. Public Participation and Involvement
  3. Illicit Discharge Detection and Elimination
  4. Construction Site Runoff Control
  5. Post-Construction Runoff Control
  6. Pollution Prevention

According to the latest Census, Kentucky’s urban population increased 2.6% between 2000 and 2010.  This trend is expected to continue.  At present ~65% of Kentucky’s population resides in the 32 counties with MS4 communities.  In time, there will be larger and more MS4 communities and thus more potential for water quality impairments associated with urban areas. 

Regardless of whether your county contains a stormwater permitted community, or the type of sewer systems (combined or separate) in your communities, education about stormwater is a critical component to improving and preserving natural resources.