Weld County MS4

MS4 Area Map(PDF, 1MB) Weld County currently holds a federally-mandated Municipal Separate Storm Sewer System (MS4) Permit issued by the Colorado Department of Public Health and Environment (CDPHE) for all unincorporated urban areas within the County. As required by the permit, a Stormwater Management Program was developed with a goal of reducing the amount stormwater pollution entering local creeks, streams and rivers from these urbanized areas. Urbanized areas are determined by US Census data, which is updated every 10 years.

Learn more about what you can do to protect stormwater.

The County is tasked with implementing the six Minimum Control Measures (MCM) below.

1. Public Education and Outreach:
Educate residents and members of the business community about the impacts of stormwater on water bodies and the steps the public can take to help reduce pollutants in stormwater runoff.

2. Public Participation/Involvement:
Provide a mechanism and process to allow the public to review and provide input on the Stormwater Management Program.

3. Illicit Detection and Elimination:
Develop, implement and enforce a program to detect and eliminate spills, illegal dumping and other non-stormwater discharges into the County’s storm drainage system.

4. Construction Site Stormwater Runoff Control:
Develop, implement and enforce a program to reduce pollutants in any stormwater runoff from construction areas into the County’s storm drainage system.

5. Post-construction Site Stormwater Management:
Ensure adequate long-term operation and maintenance of stormwater Best Management Practices (BMPs) in order to prevent or minimize impacts to stormwater from new developments or redevelopments.

6. Pollution Prevention/Good Housekeeping for Municipal Operations:
Develop and implement an operation and maintenance program with the goal of preventing or reducing pollutant runoff from municipal operations.


Colorado Stormwater Council Weld County is a proud member of the Colorado Stormwater Council (CSC), an organization comprised of 82 MS4 communities working together to protect and improve stormwater quality in Colorado. CSC combines resources to provide public education and outreach on stormwater pollution throughout the state and collaborates to develop program resources to efficiently and effectively comply with state and federal stormwater regulations.

Big Dry Creek

Weld County is also active member of the Big Dry Creek Watershed Association (BDCWA), an organization currently comprised of MS4s and wastewater treatment facilities working together in an effort to protect and improve water quality in the Big Dry Creek watershed. BDCWA works hard to develop a sound scientific understanding of water quality, flow, aquatic life and habitat conditions in Big Dry Creek and uses that information to identify measures to improve stream conditions.

Local ordinances have been developed in order to comply with the County’s federally-mandated MS4 Permit. Please refer to the stormwater-related articles of the Weld County Code.

Click here for the June 2019 MS4 Code Amendment.*

Find Out if You're in the MS4(PDF, 1MB)

MS4 Municipalities Located in Weld County:

City of Greeley

City of Evans

City of Longmont

City of Brighton

Town of LaSalle

Town of Erie

Town of Windsor

Town of Firestone