A municipal separate storm sewer system (MS4) refers to the system of pipes, ditches, and/or gullies, managed by a government entity, used for stormwater collection and distribution. The release of non-stormwater discharge into a stormwater sewer system, either accidentally or purposely, is considered an illicit discharge. Illicit discharges enter the stormwater sewer system through direct or indirect connections. An example of a direct connection is wastewater piping connected to a stormwater drain. An example of an indirect connection is dumping oil straight into a stormwater drain.

• Sanitary wastewater
• Car wash wastewater
• Improper oil disposal
• Radiator flushing
• Laundry wastewater
• Spills from roadway accidents
• Improper disposal of auto and household toxins
• Improper disposal of yard waste, such as leaves

Illicit discharges flow, untreated, into the Chesapeake Bay through the county's streams, rivers and ponds, resulting in poor water quality conditions. These water bodies potentially serve as local drinking water sources, habitat for wildlife, and recreational areas used for swimming, boating and fishing. When polluted stormwater enters a storm drain, it is released into a water body, such as a stream. One common misconception is that stormwater is treated after it enters a storm drain. Typically, this is not the case. In most instances, stormwater is not cleaned or treated before entering a stream, river, pond, or bay.

• Maintain vehicles properly to prevent leaks
• Recycle used motor oil at the Cecil County Central Landfill
• Compost leaves, grass clippings, and other yard waste
• Dispose of paint and other household waste products properly
• Report direct illicit connections to the Cecil County Department of Public Works

Eliminating illicit discharges is a key component to protect water quality, guard public health and reduce negative economic impacts within Cecil County. When water bodies do not meet designated uses for drinking water, fishing, or recreation, tourism and waterfront home values may fall; fishing and shellfish harvesting can be restricted or halted; and illicit discharges can close beaches. In addition to those significant impacts, numerous fish kills and other aquatic life losses have occurred in watersheds as a direct result of illicit discharges.

In addition to the obvious economic, environmental, and health impacts, illicit discharges are regulated under the Clean Water Act. The Clean Water Act was passed in 1972 and has been amended multiple times. The most recent revision pertaining to illicit discharges is the NPDES Phase II Final Rule (1999), which includes a minimum control requirement that measures illicit discharge detection and elimination. In order to satisfy this measure, Cecil County must make a plan to include the following five components for implementation:

1. Develop a storm sewer system map that shows the location of all outfalls and the names and locations of all water of the United States that receive discharges from those outfalls
2. Prohibit, through ordinance, non-stormwater discharges into the storm sewer system and implement appropriate enforcement procedures and actions
3. Develop and implement a plan to detect and address illicit discharges to the MS4
4. Educate public employees, businesses, and the general public of hazards associated with illicit discharges and improper waste disposal
5. identify the appropriate best management practices and measurable goals for this minimum measure