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. More information can be found on our MS4 brochure.

In Colorado, the department has issued three general MS4 permits: standard, non-standard, and Cherry Creek Reservoir Basin. General permits are written to cover a similar 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.

Statewide standard MS4 general permit (COR090000)

• Application - PDF form.
• Application - Word.
• 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 in the electronic records drawer. To search the electronic records drawer:
    • 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 use the user guide.

Statewide non-standard MS4 general permit (COR070000)

• New Permittee Application - PDF Form.
• Renewal Permittee Supplemental Application
  • Letter
  • Application (Deadline was July 16, 2021)
  • Application & renewal permit FAQs
• Current Permit. - issued 9/30/21, effective 11/1/21, expires 10/31/26.
• COR070000 Documents and modifications.
• Urban area maps webpage
• Permit implementation guidance
• Guidelines for identifying receiving waters
• 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 in the electronic records drawer. To search the electronic records drawer:
    • 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 use the user guide.

Cherry Creek Reservoir Basin MS4 general permit (COR080000)

• Application - PDF form.
• Application - Word.
• 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.
• Appendix A.
• Former COR080000 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 in the electronic records drawer. To search the electronic records drawer:
    • 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 use the user guide.

In Colorado, we issue general permits for Phase II MS4s. These permits are for small permittees as defined by EPA. These permittees are generally government entities that serve a population of less than 100,000 and are located in an “urbanized area” as defined by the US Census Bureau. These permittees can also include non-traditional MS4s such as public universities, schools, transportation districts, hospitals, and prison complexes. 

Urbanized areas throughout Colorado can be accessed on our urban area maps webpage. 
 

Statewide standard MS4 general permit (COR090000) qualifications

Governmental entities such as cities, towns, and counties that serve a population of less than 100,000 and are in an urbanized area. 

If one portion of a city or town is considered an urbanized area, that allows the entire municipality to meet the qualifications of a small MS4. The entire city or town would be the permitted area.

Counties will determine their permitted area based on their urbanized areas. Counties do not have to implement this permit outside of the permitted area.
 

Statewide Non-Standard MS4 General Permit (COR070000) qualifications

Publicly-owned systems similar to MS4s in cities and counties that are designed for a maximum daily user population (residents and individuals who come there to work or use the MS4 facilities) of at least 1,000, located in an urbanized area. 

These permittees are school districts, colleges/universities, metropolitan districts, health authorities, transportation authorities, recreation districts, urban stormwater districts, etc.

Cherry Creek Reservoir Basin MS4 General Permit (COR080000) qualifications

Publicly-owned systems and governmental entities that would require either a standard or non-standard MS4 general permit 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.