Storm Water Terms I - M

  • Illicit discharge
    A discharge to an MS4 that is not entirely composed of storm water, except authorized discharges identified in the Storm Water Management Programs.

    There are many sources of illicit discharges. Illegal dumping activities lead to illicit discharges, which is one of the reasons reducing illegal dumping is a large part of the storm water program. Oil and grease dumped into storm drains, and other activities of that nature are also considered illicit discharges. It is important to remember that whatever is dumped into storm drains, creeks, streams, lakes, and ditches ends up in our lakes completely untreated.
  • Major outfall
    An outfall that discharges from a single pipe with an inside diameter of 36 inches or more, or its equivalent (discharge from a single conveyance other than a circular pipe which is draining an area greater than 50 acres.)
    Major outfalls represent the points where polluted storm water runoff enters an MS4, or one of our waterways. It is important to remember that it is not a point source, because it represents a large drainage area, as opposed to a pipe coming directly from a facility or building.
  • Maximum extent practicable
    The technology-based discharge standard for MS4s to reduce pollutants in storm water discharges that was established by CWA Section 402(p). A more detailed discussion of MEP as it pertains to small MS4s can be found at 40 CFR 122.34.

    To the maximum extent practicable allows operators of small MS4s to use means available and easily acquired in order to reduce pollution. This alleviates undue stress on small MS4s. Storm water programs can become expensive, or require more personnel. As a governmental entity with budget constraints, this is not always possible. Therefore, the MS4 operator is allowed to implement those procedures they can, without worrying about large increases in personnel or budget.
  • Municipal separate storm sewer system (MS4)
    The system of conveyances owned and operated by the County and designed or used for collecting or conveying storm water, and which is not used for collecting or conveying sewage, including:
    • Catch basins
    • County maintained streets
    • Curbs
    • Ditches
    • Gutters
    • Man-made channels
    • Roads with drainage systems
    • Sidewalks
    • Storm drains

      The County is responsible for making sure that water being conveyed through County-owned MS4s is not polluted. One way to ensure this does not happen is to make sure that water flowing into County MS4s is not contaminated. It is important that everyone does their part not to introduce pollution into our waterways.