MS4 general permits

Municipal separate storm sewer system (MS4) permits are issued for discharges of urban stormwater into streams, rivers, and lakes. This permitting process helps keep state waters clean enough to support recreational use and aquatic life. Our MS4 brochure provides more information.

In Colorado, the department has issued three general MS4 permits: statewide small MS4s, statewide non-standard MS4s, and small MS4s within the Cherry Creek Reservoir Basin. General permits are written to cover a group of permittees. Each permittee must submit an application to be covered by the general permit. Please visit our MS4 individual permits webpage to learn more about MS4 permits issued to a single permittee.

The division is in the process of renewing the COR080000 and COR090000 small MS4 general permits. For stakeholder information, please visit our MS4 general permit renewal webpage.

Application - PDF form.
Permit - issued 4/15/16, effective 7/1/16, expires 6/30/21, and is administratively extended.
Fact sheet.
Fact sheet modification 1.
Fact sheet modification 2.
Fact sheet modification 3.
Fact sheet modification 4.
Fact Sheet modification 6.
Appendix A.
Former COR090000 general permit - for use in complying with the requirements of Part I.H of the currently effective permit.
How can I find my issued certification and other information about my permit? Issued certifications and all public documents on a permit are available online through environmental records. To search the environmental records online:
- Under search type, select CDPHERM WTR CW Search.
- Under CDPHERM Container, type in your certification number or
  permit number.
- If you have difficulty finding your permit, please refer to
  the user guide.

New Permittee Application - PDF Form.
Renewal Permittee Supplemental Application
- Letter
- Application (Deadline was July 16, 2021)
Current Permit. - issued 9/30/21, effective 11/1/21, expires 10/31/26.
COR070000 Documents and modifications.
Urban area maps webpage
Renewal stakeholder materials
Former COR070000 general permit - for use in complying with the requirements of Part I.H of the currently effective permit.
How can I find my issued certification and other information about my permit?
Issued certifications and all public documents on a permit are available online through environmental records.
- To search the environmental records online:
  - Under search type, select CDPHERM WTR CW Search.
  - Under CDPHERN Container, type in your certification number or
    permit number.
  - If you have difficulty finding your permit, please refer to
    the user guide.

Application - PDF form.
Permit - issued 4/15/16, effective 7/1/16, expires 6/30/21, and is administratively extended.
Fact sheet and (Appendix A).
Fact sheet modification 1.
Fact sheet modification 2.
Fact sheet modification 3.
Fact sheet modification 4.
Former COR080000 general permit - for use in complying with the requirements of Part I.H of the currently effective permit.
Regulation 72: Cherry Creek Reservoir control regulation.
How can I find my issued certification and other information about my permit? Issued certifications and all public documents on a permit are available online through environmental records. To search the environmental records online:
- Under search type, select CDPHERM WTR CW Search.
- Under CDPHERM Container, type in your certification number or
  permit number.
- If you have difficulty finding your permit, please refer to the user guide.

In Colorado, the division issues general permits for small MS4s. Small MS4s are defined by EPA in the Phase II Regulations and in Colorado regulations. These permittees are generally government entities that serve a population of less than 100,000 and are located in an “urban area” with a population of 50,000 or more people as defined by the U.S. Census Bureau. These permittees can also include non-traditional MS4s such as public universities, schools, transportation districts, hospitals, and prison complexes, which are regulated under the COR070000 permit.

The COR080000 permit is distinguished from the COR090000 permit in that it is issued to small MS4s that are within the Cherry Creek Watershed. This permit was created to encompass additional requirements stemming from Regulation 72, which regulates the Cherry Creek Reservoir Basin.

Maps of urban areas with a population of 50,000 or more people can be accessed on our urban area maps webpage.