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.


New permit applications due within 180 days

 New permittees have 180 days to submit an application, after receipt of letter from the division. 

More information is available on our FAQ.


Links to permits, fact sheets, and applications


Statewide standard MS4 general permit (COR090000)

Statewide non-standard MS4 general permit (COR070000)

Cherry Creek Reservoir Basin MS4 general permit (COR080000)

Qualifications for coverage under an MS4 small general permit

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. 


Other permitting information


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MS4 permits are handled by the Permits Section, Unit 1.

Please contact either