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Treating On-Site Runoff

Stormwater runoff from developed land contains sediment, bacteria and other pollutants that can harm streams and aquatic life. To minimize potential impact on our surface waters, the City of Longmont requires all developments disturbing over one-acre of land (or that are otherwise a part of a common plan of development) to design and construct on-site permanent stormwater control measures. These treatment facilities - also known as Permanent Best Management Practices (BMPs) – must be constructed in accordance with the City's adopted design criteria. Once construction is complete, they must be continually operated and maintained by property owners for the lifetime of the facility.

Verification of proper design, as well as the establishment of long-term operation and maintenance responsibilities, is managed through the City’s Permanent Stormwater Control Permit system, as described in more detail below.


When properly designed, constructed, and maintained, Permanent Stormwater Control (PSC) features reduce pollutants in stormwater runoff from developed land. PSC Permits are used by the City to verify all three of these phases meet the requirements outlined in Title 14.26 of the City of Longmont Municipal Code.

Design Phase

Technical design documentation is submitted as a part of the larger Design Review process, typically coordinated by the Planning or Engineering Services divisions. This documentation allows us to verify the proposed design meets the established design criteria. The 'PSC Submittal Checklist' linked to the right provides a succinct summary of submittal requirements for a PSC Design Plan.

Construction Phase

Once the PSC Design Plan is approved, it is the responsibility of the PSC Permit holder to install their PSC facilities to these specifications. As-built drawings must be stamped by a licensed engineer and submitted to City staff for review and approval prior to the end of construction activities.

Once the PSC as-builts are approved, the facility formally begins operation.

Operations and Maintenance Phase

A permitted PSC facility must remain in place for the lifetime of the development, and requires continual, on-going maintenance to function properly. An Operations and Maintenance Plan is included with the permit documentation, which is intended to outline all permit holder responsibilities. These responsibilities include, among other items, submitting an annual report to the City summarizing all maintenance activities undertaken by the permit holder. Formal annual reporting forms are provided in the O&M Manual.

All questions regarding PSC Permits should be directed to Environmental Services.

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