Environmental Snapshot: Construction Stormwater in Colorado

Colorado: A Headwaters State

Colorado is a headwaters state, meaning many major western rivers including the Colorado, Arkansas, South Platte, and Rio Grande begin here. Water leaving a construction site in Colorado can travel hundreds of miles downstream, serving communities, agriculture, and ecosystems across multiple states.

Why Stormwater Control Matters

Colorado’s steep terrain, intense storms, and snowmelt make construction sites especially vulnerable to erosion. Sediment is the most common pollutant from construction activities and can degrade water quality, damage habitat, transport fuels and concrete washout, and impact drinking water and irrigation systems.

Pictured below is a steep slope and culvert with erosion logs at the base from United Companies Winter Park project. Controlling the live stream during grading was challenging, but the team managed it with erosion logs and regular maintenance until the slope stabilized.

The 6&20 project photos below show a pad where equipment is setting and erosion logs have been placed to prevent the new looser soil from running into the channel or stream. The project team reseeded this area as part of the stormwater mitigation plan. The restoration work will stabilize soil and improve runoff control.

Permit Coverage & Responsibilities

Most construction sites disturbing one acre or more or part of a larger common plan require coverage under Colorado’s Construction Stormwater Permit. Key requirements include a Stormwater Management Plan (SWMP), routine inspections, installation and maintenance of stormwater control measures (CMs), timely repairs, and final stabilization.

Control Measures (CMs)

Stormwater control measures formerly known as Best Management Practices (BMPs) are required features used to prevent sediment and pollutants from leaving the site. Common examples include silt fence, wattles, stabilized entrances, slope protection, inlet protection, concrete washout areas, and good housekeeping.

The orange inlet sediment bags block the gutter drain as inlet protection on one of the United Companies milling projects in Avon. This prevents millings from leaving the site and entering the storm inlet.

Everyone Has a Role

Stormwater compliance is a shared responsibility. Field crews, operators, and supervisors all play a role in maintaining controls and addressing issues early. Building responsibly in Colorado means protecting water at its source. Effective stormwater management helps safeguard the headwaters that serve the entire region.

By the Rockies South Environmental Team, with major contributions from Environmental Technician, Jesse Farmer.