Environmental Rules in Longmont, CO (2026)
4 verified environmental rules for Longmont, Colorado, sourced directly from the municipal code and official government pages.
Verified from official government sources
Stormwater Management
Longmont bans any non-stormwater discharge into its municipal storm sewer system, covering hazardous chemicals, construction runoff and other pollutants, with narrow listed exemptions and daily civil penalties for violations.
Longmont Stormwater Discharge Prohibition
Heavy RestrictionsLongmont Municipal Code § 14.26.050
Non-stormwater discharges to the city's MS4 are prohibited. Illegal non-stormwater discharges include, but are not limited to, discharges that: 1. Cause or contribute to violations of the city's MS4 general permit; 2. Cause or contribute to any blockages of or damage to the MS4; 3. Constitute a fire or explosion hazard; 4. Contain any toxic or hazardous material, including, but not limited to, ...
Erosion Control
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.
Longmont Construction Erosion Control Permit
Significant RestrictionsLongmont Municipal Code § 14.26.120
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.
Flood Zones
Longmont Municipal Code section 20.12.030 requires a floodplain development permit before any building, fill, or land-use change proceeds within a special flood hazard area. The director of public works and natural resources serves as floodplain administrator, reviewing applications and enforcing standards that track National Flood Insurance Program minimums. Violators face daily fines under chapter 1.12 and nuisance injunctions, while property owners keep a variance and judicial-review path through the board of adjustment.
Longmont Floodplain Development Permit Rules
Some RestrictionsLongmont Municipal Code §§ 20.12.030, 20.12.040, 20.16.060
Sec. 20.12.030. - Establishment of floodplain development permit. A floodplain development permit shall be required to ensure conformance with the provisions of this title. Sec. 20.12.040. - Compliance. No structure or land shall hereafter be located, altered, or have its use changed within the special flood hazard area without full compliance with the terms of this title and other applicable ...
Flood Elevation Requirements
Longmont requires new and substantially improved residential structures in mapped flood zones to elevate the lowest floor one foot above the base flood elevation, certified by a licensed engineer or surveyor.
Longmont Base Flood Elevation Freeboard
Some RestrictionsLongmont Municipal Code § 20.20.020
New construction and substantial improvement of any residential structure shall have the lowest floor (including basement), electrical, heating, ventilation, plumbing, and air conditioning equipment and other service facilities (including ductwork), elevated to one foot above the base flood elevation. Upon completion of the structure, the elevation of the lowest floor, including basement, shall...
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