Longmont, CO Environmental Rules: Erosion Control (2026)

Longmont enforces erosion and sediment control under LMC Chapter 14.26 and the 2025 City of Longmont Design Standards. Every construction site — public or private, residential or commercial — must implement BMPs sufficient to prevent sediment, concrete washout, fuel, and other pollutants from leaving the property and entering the MS4. Typical BMPs required by the Design Standards include silt fence at the down-gradient site perimeter, vehicle tracking control pads at all egress points, inlet protection on adjacent storm drains, stabilized stockpiles, concrete washout containment, perimeter berms, and prompt seeding or mulching of disturbed areas. Sites disturbing one acre or more must also enroll in the State CDPS Stormwater Construction Permit administered by CDPHE under the Colorado Water Quality Control Act and maintain a written Stormwater Management Plan (SWMP) on site for inspection. The city's MS4 program requires that Longmont inspectors have access to the SWMP and the site at reasonable times. The building permittee — not the developer or general contractor — carries personal responsibility for erosion control tied to a building permit. Failure to install BMPs before ground disturbance is one of the most common stop-work triggers issued by the city.