To: Board of County Commissioners
Through: Bryan Weimer, Director, Public Works and Development
Prepared By:
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Lisa Knerr, Environmental Program Manager, Engineering Services Division
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presenter
Presenter: Lisa Knerr, Environmental Program Manager, Engineering Services Division
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Subject:
title
Grading, Erosion, and Sediment Control (GESC) Manual Updates
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Purpose and Request:
recommended action
Public Works & Development (PWD) would like to discuss the changes to the County’s Grading, Erosion, and Sediment Control (GESC) Manual, answer questions from the Commissioners, and seek direction on proposed changes to the County’s GESC Manual.
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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 BOCC last approved changes to the GESC Manual on December 6, 2022 (Resolution Number 22-360).
In general, these proposed revisions clarify that the County can implement the GESC Manual requirements, better describes the partnership between the Southeast Metro Stormwater Authority (SEMSWA) and the County, removes unclear or unnecessary language, and provides other language to clarify sections of the GESC Manual. These proposed revisions should not change any day-to-day operations of either SEMSWA or County staff or affect any costs to GESC permittees.
The redlined version attached to this BSR reflects the changes from SEMSWA/Centennial’s GESC Manual approved in 2025.
Minor Changes-Should not affect permittee applications, staff application review times, or costs to GESC permittees.
• Throughout the Manual
o Updated the formatting to be consistent throughout the document.
o Replaced references to SEMSWA throughout the document with a clear delegation section in 1.6.
o References to SEMSWA’s delegation and Section 1.6 at the beginning of each Chapter.
o Continue to use the term “approved” versus SEMSWA’s use of the term “accepted”. The current GESC Manual uses the term “approved”.
• Table of Contents
o The Table of Contents has been updated to reflect the proposed changes.
• Chapter 1
o Revised language in Chapters 1 to clarify the partnership with SEMSWA and give them delegation to implement the majority of the Manual in their service area. SEMSWA will not implement the GESC program outside of their service area, issue Single-Family Residential Lot Erosion Control Certificates, or prosecute GESC violations. SEMSWA will continue to follow the County’s Enforcement Response Plan.
Added a map to clarify the County’s MS4 permit area and SEMSWA’s service area.
Alternatives: The alternative would be for the BOCC to decline to approve the proposed changes to the GESC Manual.
Fiscal Impact: The adoption of the revised GESC Manual is not expected to result in a significant increase in staff resources.
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.”
Staff Recommendation: Staff recommends the proposed changes to the GESC Manual. As such, staff requests direction to bring these items to public meeting for Board approval.
Concurrence: SEMSWA