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Skyway’s Municipal Separate Storm Sewer System (MS4) Program

What is a MS4 permit?

Under the Clean Water Act, municipalities and entities in urbanized areas are under a federal mandate to obtain a National Pollution Discharge Elimination System (NPDES) permit for discharges of Small Municipal Separate Storm Sewer Systems (MS4) (Throughout the state of Illinois the NPDES General Stormwater permit is issued by the Illinois Environmental Protection Agency (IEPA), also referred to as the ILR40 (MS4) permit. The MS4 permit requirements include a stormwater management program for reducing impacts from stormwater runoff by issuing MS4 permits.

What is stormwater runoff?

Stormwater runoff occurs when precipitation from rain or snowmelt flows over the ground. Impervious surfaces like driveways, sidewalks, and streets prevent stormwater from naturally soaking into the ground. Click for more information.

What is included in a MS4 permit?

As part of the MS4 permit, the permittee is required to implement a stormwater management program with six minimum control measures and special conditions to be included in the program. These six minimum control measures are as follows:

Six (6) minimum control measures

1. Public Education & Outreach: The public education and outreach consists of measures and programs to educate the public about the impacts of stormwater discharges to receiving waterways and management practices to reduce pollution in stormwater. 

2. Public Involvement/Participation: The public involvement and/or participation consists of meetings, resources, and events to promote the public participation in environmental programs. 

3. Illicit Discharge Detection and Elimination: The illicit discharge detection and elimination consists of developing, implementing, and enforcing a program to detect and eliminate stormwater pollution.

4. Construction Site Storm Water Runoff Control: The construction site storm water runoff control measure consist of developing, implementing, and enforcing a program to reduce pollutants in storm water runoff from construction activities with 1 acre or more of disturbance. 

5. Post-construction storm water management in new development and redevelopment: The post-construction storm water management measure consist of activities to reduce pollutants in storm water runoff, including best management practices and maintenance.

6. Pollution Prevention/Good Housekeeping for Municipal Operations: Pollution prevention and/or good housekeeping measures consist of educating and training Skyway staff to prevent and reduce stormwater pollution from Skyway owned operations.


How is the Skyway managing stormwater?

The Skyway developed a stormwater management program to reduce pollutant impacts in stormwater runoff. The MS4 permit required monitoring, record keeping, and reporting documents consists of the following:

  • Notice of Intent (NOI) - NOI is available to the public by IEPA  or contact to request a copy.

  • Stormwater Pollution Prevention Plan (SWPPP) - SWPPP is available to the public by IEPA or contact to request a copy.

  • Salt Usage-Yearly salt usage during hte winter months is available in the SWPP or contact us to receive a copy.

  • Storm Water Management Plan (SWMP) - SWMP is available to the public by IEPA or by contacting us to receive a copy.

  • Annual Report - 2023 Annual Report and/or Annual reports for subsequent years are available to the public. Contact us to receive a copy. 

  • Monitoring - Monitoring results are included in the annual reports, in accordance to the latest permit requirements

  • Annual Training - Training of Skyway employees on storm water management is conducted annually. The 2022 training was completed in October

In a continual effort to improve the way the Skyway manages the reduction of pollutant impacts in stormwater runoff, we encourage public involvement and comments on the above information. Please direct all comments to environmental@chicagoyskyway.org.


How is the Skyway managing chlorides?

In the Chicago region, elevated chloride concentrations in receiving streams during the winter season is primarily due to road salt. Implementing control measures is important to reduce chlorides discharged into receiving waterbodies. The Skyway’s commitment to proper management of chlorides includes the following activities:

  • Participation in an active watershed group - Chicago Area Waterways Chloride Workgroup (CAWCW).

  • Salt storage - The Skyway covers their salt storage pile with a secured tarp during the off season. When the salt storage pile is in use for winter maintenance operations, the working face is currently left uncovered. The Skyway is exploring methods of covering the working face on a more permanent basis.

  • Tracking Salt Usage - The Skyway tracks average annual salt usage for de-icing purposes per calendar year. 

Other related links:

Map of Effective Water Quality Standard of CAWs area


As a Resident, how can I help?

As a resident, you can play an active and vital role in stormwater management in your area. Below are 10 things you can do to prevent stormwater runoff pollution (United States Environmental Protection Agency)

  1. Use fertilizers sparingly and sweep up driveways, sidewalks, and gutters

  2. Never dump anything down storm drains or in streams

  3. Vegetate bare spots in your yard

  4. Compost your yard waste

  5. Use least toxic pesticides, follow labels, and learn how to prevent pest problems

  6. Direct downspouts away from paved surfaces; consider starting a rain garden

  7. Take your car to the car wash instead of washing it in the driveway

  8. Check your car for leaks and recycle your motor oil

  9. Pick up after your pet

  10. Have your septic tank pumped and system inspected regularly

Other Related Links:

Interactive Water Cycle (K-12) 

Trash Free Waters

Soak up the Rain with Green Infrastructure