Longmont, CO Environmental Rules: Erosion Control (2026)
Key Facts
- Permit trigger
- 1+ acre disturbed
- Phased projects
- Also count toward the 1-acre trigger
- Site plan content
- Erosion control plan required
- Permit term
- Two years
Summary
Construction disturbing one acre or more in Longmont requires a stormwater construction activity permit, with a site plan showing erosion and sediment control measures, before any grading or dirt work begins.
It shall be unlawful for any person to conduct any construction activity resulting in the following total disturbed area without first obtaining a stormwater construction activity permit for such construction activity: 1. One acre or more; 2. Less than one acre if such activities are part of a larger common plan of development, or sale, that would disturb one or more acres.
Full Breakdown
Longmont Municipal Code § 14.26.120 makes it unlawful to conduct construction disturbing one acre or more, or a smaller area that's part of a larger phased plan totaling an acre or more, without first obtaining a stormwater construction activity permit. Under § 14.26.140, the site plan supporting that permit application must include erosion control plans showing site grading and contours, plus the locations of the structural and nonstructural erosion and sediment control measures that will keep pollutants out of the storm sewer. The construction permit runs for two years from issuance.
Violations & Fines
Starting disturbance without the required permit is unlawful under § 14.26.120 and is enforced the same as any chapter 14.26 violation: a strict-liability offense under § 14.26.160 with fines up to $999 or jail up to 180 days, plus civil penalties up to $500 per day under § 14.26.210.
Frequently Asked Questions
When does a Longmont construction project need a stormwater/erosion control permit?
What must the erosion control plan for a Longmont permit show?
Sources & Official References
Other rules in Longmont
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Erosion Control in Nearby Cities
How other cities in Boulder County handle erosion control.