Municipal Separate Storm Sewer System (MS4) Main Page
Polluted stormwater runoff is commonly transported through Municipal Separate Storm Sewer Systems (MS4s), from which it is often discharged untreated into local waterbodies. To prevent harmful pollutants from being washed or dumped into an MS4, operators must obtain a NPDES permit and develop a stormwater management program.
- Phase I, issued in 1990, requires medium and large cities or certain counties with populations of 100,000 or more to obtain NPDES permit coverage for their stormwater discharges.There are approximately 750 Phase I MS4s.
- Phase II, issued in 1999, requires regulated small MS4s in urbanized areas, as well as small MS4s outside the urbanized areas that are designated by the permitting authority, to obtain NPDES permit coverage for their stormwater discharges. There are approximately 6,700 Phase II MS4s.
Generally, Phase I MS4s are covered by individual permits and Phase II MS4s are covered by a general permit. Each regulated MS4 is required to develop and implement a stormwater management program (SWMP) to reduce the contamination of stormwater runoff and prohibit illicit discharges.
WHAT IS AN MS4?
An MS4 is a conveyance or system of conveyances that is:
- Owned by a state, city, town, village, or other public entity that discharges to waters of the U.S.;
- Designed or used to collect or convey stormwater (including storm drains, pipes, ditches, etc.);
- Not a combined sewer; and
- Not part of a Publicly Owned Treatment Works (sewage treatment plant).
WHAT CAN I FIND ON THIS WEB SITE?
EPA's MS4 Program Highlights
To access the full list of NPDES stormwater information, use the navigation tool box on the right side of this page.
- Revised Memorandum on Stormwater Permits and TMDLs (PDF) (12 pp, 444K, About PDF) - Updates 2002 memorandum addressing the establishment of wasteload allocations (WLAs) for stormwater discharges in Total Maximum Daily Loads (TMDLs) and water quality-based effluent limits in NPDES permits for stormwater discharges.
- MS4 Permit Compendium (PDF) (38 pp, 2.3MB, About PDF) - Compiles example EPA and State MS4 permits that include post-construction performance standards and effluent limitations that implement approved TMDLs for impaired waterbodies.
- Stormwater Phase II Final Rule Fact Sheet Series - Provides an overview of the major elements of the Final Phase II Rule, including small MS4 programs, minimum control measures, and permitting.
- National Menu of BMPs - Best management practices (BMPs) that can be used to meet the six minimum measures.
- Urbanized Area Maps - Includes a set of digitized maps for each urbanized area as defined by the 2000 US Census with one map containing an overview of the urbanized area and another detailed map with street level features.
- MS4 Webcasts - EPA webcasts for local stormwater professionals on the six minimum measures.
- MS4 Program Evaluation Guidance - Developed to help NPDES authorities evaluate the quality of Phase I and Phase II MS4 programs.
- Measurable Goals Guidance for Phase II Small MS4s (55 pp, 624K, About PDF) - Designed to help small MS4 operators comply with the measurable goals permitting requirements.
- MS4 Permit Improvement Guide (119 pp, 2.11MB, About PDF) - The primary purpose of this Guide is to assist permit writers in strengthening municipal separate storm sewer system (MS4) stormwater permits.
Federal Government and Stormwater Fees
- Federal Government Obligations to Pay Stormwater Fees (2 pp, 119K, About PDF) - On January 4, 2011, President Obama signed into law "An Act to Amend the Federal Water Pollution Control Act to clarify Federal responsibility for stormwater pollution," Pub. L. No. 111-378, 124 Stat.4128 (2011) to clarify that reasonable service charges payable by federal agencies, as described in Section 313(a), include certain storm water assessments.
- Memorandum Clarifying that New Legislation Provides for Stormwater Fees to be Paid from Current Lump-sum Appropriations (13pp, 196K, About PDF) - On March 18, the Departmnet of Justice/Office of Legal Counsel released a memorandum to clarify that language in Section 313(c)(2)(B) of the Clean Water Act contained in new legislation obligating Federal agencies to pay stormwater managements fees does not impose a specific appropriation requirement. Stormwater assessments are payable from annual, including current, lump-sum appropriations.
Fact Sheets on Key Municipal Stormwater Program Issues (Developed by EPA Region 3)
- Evaluating the Effectiveness of Municipal Stormwater Programs (6 pp, 374K, About PDF) - A fact sheet for municipalities on how to evaluate the effectiveness of their municipal stormwater programs.
- Funding Stormwater Programs (5 pp, 217K, About PDF) - A fact sheet for municipalities on alternatives for funding their stormwater program.
- Incorporating Environmentally Sensitive Development Into Municipal Stormwater Programs (7 pp, 440K, About PDF) - A fact sheet for municipalities on how to encourage or require low impact development practices to meet stormwater goals.
- Understanding Impaired Waters and Total Maximum Daily Load (TMDL) Requirements for Municipal Stormwater Programs (5 pp, 615K, About PDF) - A fact sheet for municipalities on how to determine if their storm drain system discharges to an impaired waterbody and how to upgrade their stormwater management programs to address the TMDL.
Minimum Control Measures
The MS4 Program contains elements called minimum control measures that when implemented should result in a significant reduction in pollutants discharged into receiving waters. The minimum measures are outlined below:
- Public Education/Outreach and Participation/Involvement - Describes BMPs that involve the public in developing, implementing, and reviewing MS4 management programs and describes ways to reduce stormwater pollution.
- Public Outreach Fact Sheets and Webcasts
- Getting In Step: A Guide for Conducting Watershed Outreach Campaigns (136 pp, 3.3MB, About PDF) - Describes some of the tools needed to develop and implement an effective watershed outreach plan.
- Getting In Step: Engaging and Involving Stakeholders in Your Watershed (80 pp, 1.34MB, About PDF) - Describes the tools needed to effectively identify, engage, and involve stakeholders throughout a watershed.
- Nonpoint Source (NPS) Outreach Toolbox - Provides educational materials and other useful links for educating the public on nonpoint source pollution or stormwater runoff.
- Stormwater Manager's Resource Center
- Illicit Discharge Detection and Elimination (IDDE) - Describes BMPs for identifying and eliminating illicit discharges and spills to storm drain systems.
- IDDE Fact Sheets and Webcasts
- IDDE Guidance Manual (378 pp, 9.3MB, About PDF)- Outlines practical, effective IDDE techniques for MS4s.
- IDDE Supporting Materials - Provides support and guidance to Phase II communities developing IDDE programs.
- Construction Site Runoff Control - Describes BMPs for MS4s and construction site operators to address stormwater runoff from active construction sites.
- Construction Fact Sheets and Webcasts
- Developing Your Stormwater Pollution Prevention Plan: A Guide for Construction Sites - Provides helpful guidance, including SWPPP templates and a sample inspection form, for operators who must prepare a SWPPP to obtain NPDES permit coverage for their stormwater discharges.
- Post-Construction Runoff Control - Describes BMPs for MS4s, developers, and property owners to address stormwater runoff after construction activities have ended.
- Post-Construction Fact Sheets and Webcasts
- Managing Stormwater in Your Community: A Guide for Building an Effective Post-Construction Program - Developed by the Center for Watershed Protection for EPA to provide stormwater professionals with practical guidance, insights, and tools to build effective programs. The guide is accompanied by several downloadable “tools" that are designed to be used and modified by local stormwater managers to help with program implementation.
- Urban Stormwater Retrofit Practices Manual - Developed by the Center for Watershed Protection highlighting retrofit practices that can capture and treat runoff before it is delivered to waterbodies.
- Reducing Stormwater Costs through Low Impact Development (LID) Strategies and Practices - Contains 17 case studies from developments across North America that examine the economic viability of LID practices compared to traditional stormwater management design practices.
- Monitoring to Demonstrate Environmental Results: Guidance to Develop Local Stormwater Monitoring Studies Using Six Example Study Designs (PDF) (176 pp, 2.16MB, About PDF) - This manual presents six monitoring study designs that can be used by Municipal Separate Storm Sewer System (MS4) communities to assess their local stormwater programs.
- Pollution Prevention/Good Housekeeping Fact Sheets and Webcasts
- Stormwater Wet Pond and Wetland Management Guidebook (80 pp, 4.12MB, About PDF) - This guidebook discusses inspection and maintenance practices at existing ponds and wetlands.
- Municipal Pollution Prevention/Good Housekeeping Practices Manual - This manual focuses on control and reduction of stormwater pollution and addresses local subwatershed restoration goals and objectives.(Manual 9)
- Street Sweeping/Storm Drain Cleanout Study Manual (73 pp, 1.11MB, About PDF) - This manual provides information to support pollutant removal efficiencies for street sweeping and storm drain cleanout practices for Phase I and II communities in the Chesapeake Bay watershed.
- Guidance for Municipal Stormwater Funding (PDF) (140 pp, 1MB) - Developed by the National Association of Flood and Stormwater Management Agencies (NAFSMA) under a grant provided by EPA in January 2006 to provide funding guidance for stormwater utilities.
- Clean Water State Revolving Fund (CWSRF) - Describes funding options for a wide variety of water quality projects.
- Nonpoint Source (319) Grant Program - Provides grant money, under section 319 of the Clean Water Act, to states, territories, and Indian Tribes to support activities part of an approved Nonpoint Source Management Program.
- Catalog of Federal Funding Sources for Watershed Protection - Searchable database of financial assistance sources (grants, loans, cost-sharing) available to fund a variety of watershed protection projects.