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National Information |
Stormwater - Permits for Municipal Separate Storm Sewer Systems (MS4s)
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Storm water runoff is often transported directly from municipal collection systems to adjacent water bodies; carrying with it all of the pollutants that it comes into contact with from streets, homes, and industrial activities. |
Polluted storm water runoff is often transported to municipal storm sewer systems and ultimately discharged into local rivers and streams without treatment. Common pollutants which are discharged in storm water runoff from municipal storm sewer systems include oil and grease from roadways, pesticides from lawns, sediment from construction sites, and trash. When deposited into nearby waterways, these pollutants can impair the waterways, thereby discouraging recreational use of the resource, contaminating drinking water supplies, and interfering with the habitat for fish, other aquatic organisms, and wildlife.
EPA's storm water program regulates discharges from Municipal Separate Storm Water Systems (often referred to as "MS4s") through regulations which have been implemented in two phases:
- Phase 1 regulations - Apply to medium and large MS4s. A medium MS4 is a system that is located in an area with a population between 100,000 - 249,999, and a large MS4 is a system located in an area with a population of 250,000 or more. Other MS4s, including those under the 100,000 threshold, are also large and medium MS4s. These are systems which were designated by NPDES permitting authorities due to interrelationships to other medium and large MS4s.
- Phase 2 regulations - Apply to regulated small MS4s. A regulated small MS4 is a system located in an urbanized areas as defined by the Bureau of the Census or a system located outside of an urbanized area but designated by the permitting authority. Example criteria for designating a MS4 outside of an urbanized area include population (e.g., 10,000 people), potential for water quality impacts, and proximity to other regulated MS4s.
In accordance with federal regulations (40 CFR 122.26), operators of regulated MS4s are required to create a storm water management program. For Phase 1 MS4s, a storm water management program includes measures to:
- Identify major outfalls and pollutant loadings;
- Detect and eliminate non-stormwater discharges to the system;
- Reduce pollutants in runoff from industrial, commercial, and residential areas; and
- Control stormwater discharges from new development and redevelopment areas.
For Phase 2 MS4s, a storm water management program requires the implementation of six minimum measures:
- Public Education and Outreach
- Public Participation/Involvement
- Illicit Discharge Detection and Elimination
- Construction Site Runoff Control
- Post-Construction Runoff Control
- Pollution Prevention/Good Housekeeping
Regulated Municipal Separate Storm Sewer Systems in the EPA Region 8 States
Within the states defined by EPA Region 8 (CO, MT, ND, SD, UT, and WY), there are 8 Phase 1 MS4s. These include Denver (CO), Lakewood (CO), Aurora (CO), Colorado Springs (CO), Arapahoe County (CO), Colorado Department of Transportation (CO), Sioux Falls (SD), Salt Lake City (UT), and Salt Lake County (UT). Each of these Phase 1 MS4s is regulated via a specific individual permit and is regulated by the state environmental agency in which it is located. For more information on how these Phase 1 MS4s are regulated and/or to receive a copy of the individual permit, contact the appropriate state agency.
In the Region 8 states, there is a significantly larger number of Phase 2 MS4s, all of which are permitted through a general permit specific to the state in which they are located (excluding those located on federal facilities in Colorado, which are permitted by EPA Region 8). For a listing of all of the Phase 2 MS4s, visit the documents section of this web site under the heading Phase II Small Municipalities. For more information on these general permits and how they are implemented or enforced, contact the appropriate state or EPA Region 8.
Regulated MS4s Where EPA is the Permitting Authority
EPA has issued a general permit for storm water discharges from municipal separate storm sewer systems for regulated small MS4s on federal facilities in Colorado. This permit covers storm water discharges from the following MS4s:
- Denver Federal Center
- National Institute of Standards and Technology (Boulder Campus)
- Denver Veterans Administration Medical Center
- Fort Carson
- Federal Correctional Institution Englewood
- Peterson Air Force Base
- Buckley Air Force Base
-
US Air Force Academy
Public Comment and Review of Municipal Storm Water Programs
Each of the MS4s regulated by EPA Region 8 is covered under the Region 8 Small MS4 General Permit. This permit contains conditions under which the MS4s must meet each of the six minimum measures listed previously. Additional information describing the storm water management programs for each facility is described in the Notice of Intent (NOI) application which was submitted to EPA when applying for coverage under the general permit.
Several documents are included in the documents section of this web site which pertain to the storm water management programs which are in effect for each of these facilities. These include the NOI (Notice of Intent) applications which define measurable goals upon which each of the six Phase 2 minimum measures (listed above) will be implemented at each of these facilities, the general permit under which all of the facilities are covered, and a fact sheet which further describes the permit. To obtain a copy of any documents or additional information which is not provided in the documents section of this web site, or to make a comment or request regarding any activities which may affect the effective implementation of an effective storm water management program at any of EPA's regulated MS4s, contact:
Greg Davis:
Region 8 Storm Water Coordinator
U.S. Environmental Protection Agency, (8P-W-P)
999 18th Street, Suite 300
Denver, CO 80202-2466E-mail: davis.gregory@epa.gov
Telephone: 303-312-6314, or in the Region 8 states: 1-800-227-8917 ext. 6314
For more general information on EPA's municipal storm water program visit EPA's national MS4 web site.
