To: Board of County Commissioners
Through: Ceila Rethamel, PE, Acting Director, Public Works and Development
Prepared By:
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Lisa Knerr, Environmental Program Manager, Public Works and Development
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Subject:
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Adoption of Updated Grading, Erosion, and Sediment Control (GESC) Manual
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Purpose and Request:
recommended action
The purpose of consent agenda item is to get approval from the Board of County Commissioners (BOCC) to adopt the updates to the Grading, Erosion, and Sediment Control (GESC) Manual. The draft of the GESC Manual was presented to the BOCC on March 17, 2026, in a study session.
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Alignment with Strategic Plan: Sustainable Growth and Infrastructure - Support environmentally responsible development and energy efficiency in county operations.
Background and Discussion: The County has a permit certification from the Colorado Department of Public Health and Environment under the General Permit COR080000 Stormwater Discharges Associated with Municipal Separate Storm Sewer Systems (MS4s) that Discharge to the Cherry Creek Reservoir Drainage Basin Authorization to Discharge under the Colorado Discharge Permit System. The County’s permit number under that general permit is COR080010. The County’s MS4 permit requires the County to have a Construction Sites Program that requires “control measures to be implemented for all applicable development sites.” The MS4 permit defines an “applicable development site” as a site that results in “land disturbance of greater than or equal to one acre, including sites less than one acre that are part of a larger common plan of development or sale, unless excluded below.” The exclusions are not pertinent to the proposed revisions. The MS4 permit also requires the County to comply with Regulation 72-Cherry Creek Reservoir Control Regulation, which further requires the County to regulate all “land disturbances”. The County’s current GESC Manual meets all requirements of the MS4 permit. The most significant change to the Manual is that the City of Centennial and the Southeast Metro Stormwater Authority (SEMSWA) will no longer share the same manual as the County.
The two manuals are still very similar, but differ in the following: 1) Since the County has enforcement responsibility for the GESC Manual, the County’s Manual uses County-accepted terms in several chapters, including the Variance, Fees and Collateral, and Enforcement chapters. 2) Since SEMSWA is the County’s partner in implementing the stormwater program, the County’s Manual has a new section specifically delegating authority to implement the Manual to SEMSWA. 3) The County’s manual continues to have additional appendices for utility and oil and gas construction projects in eastern Arapahoe County and a single-family residential lot erosion control certificate. 4) The County’s Manual includes an additional 10% administration fee for the Engineer’s Cost Estimate. 5) The County’s manual follows the Associated Press style and uses the County branding standards.
The proposed updates also include the same updates that were adopted by the SEMSWA Board in July 2025 and include the following: 1) Reduction of GESC program permit categories from five to three. 2) Replacement of the GESC report with a simplified GESC Narrative Sheet. 3) Update to Engineer’s Cost Estimate to reflect current costs. 4) Revisions to Standard Notes and Details for ease of use and to improve compliance with CDPHE permits. 5) Clarification to the permit process for owner or operator changes. 6) Requirements for topsoil to proactively manage revegetation.
These proposed revisions should not change any day-to-day operations of either SEMSWA or County staff or affect any costs to GESC permittees. It is anticipated that permittees will save resources by replacing a GESC report with a simple narrative sheet. The simplified narrative sheet will also save County staff time in reviewing GESC permit applications. SEMSWA conducted outreach activities for and incorporated public comments into their version of the GESC Manual that was adopted by their Board in July 2025. These changes have been incorporated into the County’s Manual. The County posted the draft GESC Manual on their website and emailed key stakeholders in October to solicit comments from stakeholders by November 11, 2025. No comments were received as of November 3, 2025.
Alternatives: The GESC Manual may be modified to reflect public, stakeholder or BOCC comments.
Fiscal Impact: This proposal is not expected to have a fiscal impact as current staff time and resources were used for the update.
Alignment with Strategic Implementation Strategies: The attached framework helps Arapahoe County institutionalize values-based, transparent decision-making, documenting how we make decisions and carry out actions to achieve the county’s strategic plan.
Concurrence: Stakeholder input was requested from internal and external partners along with the County Attorney’s Office and Southeast Metro Stormwater Authority.