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Stormwater Phase II Background


The U.S. Environmental Protection Agency (EPA) and the Massachusetts Department of Environmental Protection (DEP) began regulating stormwater in 1990 under the National Pollutant Discharge Elimination System (NPDES) permit program. Stormwater Phase I targeted large urban areas with populations of 100,000 or greater, which included Boston and Worcester.

On December 8, 1999, the Phase II Rule of the NPDES stormwater program was published to expand the program to Municipal Separate Storm Sewer Systems (MS4s) within urban areas of populations less than 100,000 that were not addressed under the Phase I program. Objectives of the Phase II rule are to reduce the discharge of stormwater pollutants to the maximum extent practicable, to protect water quality, and to satisfy the appropriate water quality requirements of the Clean Water Act. In order for an MS4 to meet these objectives, EPA has defined the following six “minimum control measures” that are to be addressed:

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/Good Housekeeping for Municipal Operations

The intent is for MS4s to address these six minimum control measures by identifying and implementing the appropriate Best Management Practices (BMPs) that apply to their community. EPA has prepared a “menu” of BMPs to assist with this task. MS4s are to propose the selected BMPs as well as the measurable goals, time frame, and parties responsible to implement the control measures.

EPA issued a general permit for the NPDES Phase II rule that covers all MS4s. The MS4s applied for permit coverage by submitting a Notice of Intent (NOI) in 2003. This NOI identifies the applicable requirements of the general permit and lists the BMPs and stormwater programs that the MS4 will use to meet the six minimum control measures. It is required that all the BMPs and stormwater programs proposed in the NOI be developed and implemented by 2008, at which time a new five-year permit will be issued.

242 of the 351 municipalities in Massachusetts, as well as many public agencies, are now covered under Stormwater Phase I or II. For a complete list of the designated Stormwater Phase II communities, visit the following website:

Because a new general permit was not issued in 2008, the 2003 permit is still in effect.  The seventh year annual report will be due on May 1, 2010 under the existing permit.

A draft small MS4 general permit has been issued for 84 Massachusetts municipalities, and the draft permit for the rest of Massachusetts should be issued soon.  The new permit will likely include the six minimum control measures as modified, as well as provisions on: enhanced illicit discharge detection and elimination requirements, water quality monitoring, encouraged use of low impact development and green infrastructure techniques, and implementation requirements for meeting approved total maximum daily load (TMDL) studies.

For current updates on the renewal of the MS4 permit in Massachusetts, visit

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