The Colorado Department of Health and Environment (CDPHE) issues legally binding permits for the discharge of stormwater to state waters.
Their goal is to ensure that the discharge permits they issue protect the beneficial uses of those waters (domestic water supply, aquatic life, agriculture, recreation, and wetlands).
Larimer County departments engaged in construction activities regularly obtain State issued permits. It’s important that every employee working on a project for which a permit is issued understands how their job impacts the project’s compliance with their permits.
Construction Stormwater Discharge Permit - COR400000
Construction projects having a ground disturbance of one or more acres are required to obtain a Construction Stormwater Discharge Permit from the CDPHE. Applications are submitted through the CEOS system, which can be accessed from the COR400000 webpage.
Several guidance documents, a training video, and fact sheets are available in the Water Quality Training Folder and on the State’s Water Quality Construction Permits webpage.
Discharges from Construction Dewatering Activities - COG080000
This permit authorizes short-term discharges of groundwater, surface water and/or stormwater, which contacts construction activities and then discharges to waters of the state.
To learn more and apply for this permit, visit the State’s Dewatering General Permit Program webpage.Colorado Dredge and Fill Authorizations – Colorado Regulation 87
Colorado now regulates dredge and fill activities in isolated waters of the state, which are not federally regulated by the U. S. Corps of Engineers through the Clean Water Act Section 404 permitting system. Many of Colorado’s isolated wetlands and intermittent streams lost protections in 2023 with the U. S. Supreme Court’s redefinition of waters of the United States. In response, Colorado passed House Bill (HB) 24-1379, which directs the Water Quality Control Division to develop Regulation No. 87, a control regulation for avoiding, minimizing, and mitigating the impacts of dredge and fill activity in state waters. For a summary of the process view their Story Map.
Larimer County Departments now have the requirement, during the design phase of a project, to investigate whether their construction activities, involving impacts to wetlands and streams, are regulated under the Federal 404 permitting (waters of the U.S.) and/or under Colorado Reg. 87 waters of the state permitting system.
The regulation includes many excluded types of waters and exempted activities. Guidance on the Exemptions and Exclusions process is available on the Dredge and Fill webpage. If your project meets the criteria, then submit a request for an exception or exclusion.
If your project’s activities cannot be Excluded or Exempted, you may need to apply for a General Authorization (analogous to the federal Nationwide Permit System). See the Draft General Authorization for applicability and conditions. Also, Part 87.7 General Authorizations in the Draft Reg. 87 (8-1-2025). Regulation 87 should be finalized by January 1, 2026.
MS4 Water Quality Permit – COR090000
Larimer County is authorized to discharge stormwater to waters of the state from its Municipal Separate Storm Sewer System (MS4). The MS4 includes roadside swales, culverts, curb and gutter as well as other conveyances that are owned and operated by Larimer County, are within the County’s ROW and are within the County’s MS4 permit area (the urbanized areas surrounding incorporated areas).
How does this impact capital projects and operations? Projects impacting greater than or equal to 1 acre of ground disturbance are required to obtain a County issued MS4 permit from Engineering. We recommend you identify this need early in the design phase of your project so that MS4 Water Quality Staff can assist you in determining if your project can be an exempted construction activity or excluded from the requirement for permanent water quality control measures.
For more information on the County’s MS4 program and to see the permit area visit our MS4 Water Quality Webpage.
