EPA & MassDEP Requirements

The National Pollution Discharge Elimination System (NPDES) Phase II Stormwater Program became effective in Massachusetts in May 2003, and regulates Municipal Separate Storm Sewer Systems (MS4) located within urbanized areas. An urbanized area (UA), as defined by the U.S. Census Bureau, is an area with a population of at least 50,000 and a minimum average population density of more than 1,000 people per square mile. UAs are geographical areas and not limited to jurisdictional boundaries like city, town or state lines. 

Urbanized Area 2010 thumbnail Opens in new window

If we do not properly manage our stormwater runoff, our waterways and natural resources will deteriorate over time and become polluted. The Clean Water Act and the National Pollution Discharge Elimination System were enacted by Congress to protect the waters of the U.S. Failure to comply with the Clean Water Act will expose the town to fines and penalties.


Objectives of the Phase II Stormwater Program 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 a municipality to meet these objectives, EPA has defined the following "6 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 municipalities to address these six minimum control measures by identifying and implementing the appropriate Best Management Practices (BMPs) that apply to their community.

More Information

Northern Middlesex Stormwater Collaborative

Massachusetts Department of Environmental Protection Stormwater

United States Environmental Protection Agency MS4 Permit for Massachusetts