An Introduction to MS4 Stormwater Permitting

January 29, 2016
Program Update

You might hear the acronym “MS4” used often in stormwater discussions.

But what exactly does that mean? And how does it apply to stormwater permitting?

An MS4 is an acronym for a municipal separate storm sewer system. It’s a system owned or operated by a public agency, such as a city, town, county, flood control district, state, or federal agency that does not connect to the sanitary sewer system and does not lead to a wastewater treatment plant. Read more about MS4’s on the Pennsylvania Department of Environmental Protection’s (DEP) website.

We have included a copy of a power point presentation to help Pennsylvanians become more familiar with the MS4 permitting process. In addition, follow the links below to read U.S. Environmental Protection Agency (EPA) Fact Sheets addressing MS4 permit requirements. For additional references, PEC has a full list of its water resource brochures on our website as well.

Fact Sheets
  • Stormwater Overview
    Since the passage of the Clean Water Act (CWA), the quality of our Nation’s waters has improved dramatically. Despite this progress, however, degraded waterbodies still exist.
  • Small MS4 Stormwater Program Overview
    Polluted storm water runoff is often transported to municipal separate storm sewer systems (MS4s) and ultimately discharged into local rivers and streams without treatment. EPA’s Stormwater Phase II Rule establishes an MS4 stormwater management program that is intended to improve the Nation’s waterways by reducing the quantity of pollutants that stormwater picks up and carries into storm sewer systems during storm events.
  • Urbanized Areas: Definition and Description
    As discussed in Fact Sheet 2.1, Who’s Covered? Designation and Waivers of Regulated Small MS4s, the Phase II Final Rule covers all small municipal separate storm sewer systems (MS4s) located within an “urbanized area” (UA).
  • Public Education and Outreach Minimum Control Measure
    This fact sheet profiles the Public Education and Outreach minimum control measure, one of six measures an operator of a Phase II-regulated small municipal separate storm sewer system (MS4) is required to include in its stormwater management program to meet the conditions of its National Pollutant Discharge Elimination System (NPDES) stormwater permit.
  • Public Participation/Involvement Minimum Control Measure
    This fact sheet profiles the Public Participation/Involvement minimum control measure, one of six measures the operator of a Phase II regulated small municipal separate storm sewer system (MS4) is required to include in its stormwater management program to meet the conditions of its National Pollutant Discharge Elimination System (NPDES) permit.
  • Illicit Discharge Detection Elimination and Elimination Minimum Control Measure
    This fact sheet profiles the Illicit Discharge Detection and Elimination minimum control measure, one of six measures the operator of a Phase II regulated small municipal separate storm sewer system (MS4) is required to include in its stormwater management program to meet the conditions of its National Pollutant Discharge Elimination System (NPDES) permit.
  • Construction Site Runoff Control Minimum Control Measure
    This fact sheet profiles the Construction Site Runoff Control minimum control measure, one of six measures that the operator of a Phase II regulated small municipal separate storm sewer system (MS4) is required to include in its stormwater management program to meet the conditions of its National Pollutant Discharge Elimination System (NPDES) permit.
  • Post-Construction Runoff Control Minimum Control Measure
    This fact sheet profiles the Post-Construction Runoff Control minimum control measure, one of six measures that the operator of a Phase II regulated small municipal separate storm sewer system (MS4) is required to include in its stormwater management program in order to meet the conditions of its National Pollutant Discharge Elimination System (NPDES) permit.
  • Pollution Prevention/Good Housekeeping Minimum Control Measure
    This fact sheet profiles the Pollution Prevention/Good Housekeeping for Municipal Operations minimum control measure, one of six measures the operator of a Phase II regulated small municipal separate storm sewer system (MS4) is required to include in its storm water management program to meet the conditions of its National Pollutant Discharge Elimination System (NPDES) permit.

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