• NPDES- National Pollutant Discharge Elimination System.  The name of the regulatory program that addresses pollution associated with stormwater runoff.
• BMP- Best Management Practice.  This can be any activity or installed feature that is used to contain, control or treat stormwater runoff (ex. silt fences, turbidity barriers, alum treatment, street sweeping).
• NOI- Notice of Intent. An application to obtain coverage under FDEP's Generic Permit for Stormwater Discharge from Large and Small Construction Activities.
• NOT- Notice of Termination. An application to discontinue coverage under FDEP's Generic Permit for Stormwater Discharge from Large and Small Construction Activities.
• SWPPP- Stormwater Pollution Prevention Plan. A guidance document that must be prepared in conjunction with the NOI. It  addresses how a site will be managed for erosion and sediment control through the duration of the project.
• MS4- Municipal Separate Storm Sewer System. This includes the stormwater collection, conveyance and treatment system owned and maintained by a municipality (ex. inlets, street gutters, storm pipes, ditches, ponds).
• Illicit Stormwater Discharge- any discharge to an Municipal Separate Storm Sewer System (MS4) that is not composed entirely of stormwater.  Exceptions exist for discharges pursuant to an NPDES permit and the following categories of non-stormwater discharges, provided they do not cause a violation of water quality standards: water line flushing, landscape irrigation, air conditioning condensate, water from residential car washing, dechlorinated swimming pool discharges, and other similar discharges as listed in the County NPDES permit.
• Turbidity- the presence of sediment or particles stirred up or suspended in the water column. Relative to stormwater, turbidity is measured with a meter that records in nephelometric turbidity units (NTUs). All discharges from pollution sources must be no more than 29 NTUs above the background readings for the receiving waterbody. Any discharges into Outstanding Florida Waters (OFWs) must not be greater than the background conditions.

Congress enacted the Clean Water Act (CWA) in 1972 to ensure minimum water quality standards for the waters of the United States. An important part of the CWA is the National Pollutant Discharge Elimination System (NPDES) program, which addresses pollution from both point sources (pipe discharges) and non-point sources (stormwater runoff). The point source portion of the program for wastewater plants and many industries has been in existence since the start of the program, and involves individual permits for facilities. The non-point source stormwater program has been a part of the regulatory environment within Orange County since 1996, and focuses on the Municipal Separate Storm Sewer System (MS4). Orange County currently operates under NPDES permit FLS000011.

As required by 62-624.440(2), Florida Administrative Code, which adopts 40 CFR 122.26(d)(2)(iv) (United States), Orange County implemented a comprehensive Stormwater Management Program (SWMP) that includes pollution prevention measures, treatment removal techniques, stormwater monitoring, use of legal authority, and other appropriate means to effectively prohibit the discharge of non-stormwater into the MS4 and reduce the discharge of pollutants from the MS4 to the Maximum Extent Practicable (MEP). Compliance with this SWMP is reported annually in a report submitted to the Florida Department of Environmental Protection. (FDEP).

Within the Orange County Code, several sections are applicable to the control of pollutants in stormwater. More information is availble on the Orange County Codes.