Builders - Stormwater

Why do Stormwater Discharges from Construction Sites Matter?

When it rains on a construction site, stormwater flows over the site, and picks up pollutants like sediment, debris, trash and chemicals.  Unless control measures are installed on the site, those pollutants can be transported to nearby storm drains or directly into rivers, lakes and irrigation ditches.

Builders and contractors should be aware that construction activities that disturb one or more acres of land are required to get a permit for Discharging Stormwater Associated with Construction Activities  from the Colorado Department of Public Health and Environment (CDPHE). As part of operating under the State’s permit, buildings and contractors are required to implement a Stormwater Management Plan (SWMP) and Best Management Practices (BMPs; water quality control measures) to ensure proper drainage and protect water quality.

Larimer County has an MS4 Program and regulates stormwater associated with construction activities within its MS4 permit area. You can view the MS4 permit area using the Flood Indicator Map (FIL) accessed via the Land Information Locator Map (LIL).  

Once on the LIL map:

  • Click "Flood" in the Layer Themes box 
  • Click "Layer List" 
  • Open "Stormwater" by clicking the + icon
  • scroll down and select "MS4 Permit Area"
  • In "Feature Layers" make sure "Incorporated  Areas" option is selected
  • Zoom the map into your area of interest, or
  • type your address in the "Search" field, hit enter

You can access training for administering a SWMP and for installing and maintaining water quality control measures on your construction site by visiting Associated General Contractors (AGC) of Colorado.

To learn how to develop a Stormwater Management Plan (SWMP) and to find construction details for water quality control measures visit the following resources linked below.