Douglas County, CO Environmental Rules: Stormwater Management (2026)
Key Facts
- Governing section
- Zoning Resolution § 1-2709
- Max proposed slope
- 3:1 (33.3%)
- Wall barrier trigger
- retaining wall over 30 inches
- Building permit trigger
- retaining wall over 4 feet
- Contour interval cap
- 2 feet unless approved
- CO security if incomplete
- 115% of unfinished cost
Summary
New development in unincorporated Douglas County must submit a grading and drainage plan under Zoning Resolution § 1-2709, separate from the county's GESC erosion-control plan. It fixes retaining-wall barrier rules, a 3:1 maximum proposed slope, and mandatory labeling of drainage easements, detention basins, and water quality facilities before Engineering Services will approve a site plan.
§ 1-2709. Grading and Drainage Plan. The grading and drainage plan shall be prepared at the same scale as the landscape plan. Please note that this plan is separate and distinct from the GESC plan required by Engineering Services... 2. Retaining walls in excess of 30 inches in height (as measured from the lowest ground surface adjacent to the wall) used in conjunction with detention areas or ponds, or located adjacent to a pedestrian access or walking surface, shall require permanent barriers, consistent with Building Code height requirements, for the purpose of protecting the public from potential hazards. 3. Development sites are required to balance earthwork quantities on site in accordance with the GESC Manual. 4. Show existing contour lines as dashed lines (screening acceptable), and proposed contour lines as solid lines. The contour interval shall be no more than two feet unless otherwise approved by the staff planner. A. Distinguish existing grades greater than a 4:1 slope (25%). B. Proposed grades shall be no steeper than a 3:1 slope (33.3%). ... 7. Show and label the required drainage easements with detention, water quality facilities, and storm sewer infrastructure.
Full Breakdown
Douglas County splits stormwater review into two linked plans reviewed by Engineering Services: the grading and drainage plan under § 1-2709, and the separate GESC (Grading, Erosion and Sediment Control) plan required for the same project. The drainage plan must be drawn at the same scale as the landscape plan and show every proposed and existing building, wall, walk, and street. Retaining walls over four feet require a structural design and building permit, and any wall over 30 inches next to a detention pond, basin, or pedestrian walkway must include a permanent barrier consistent with Building Code height rules to protect the public.
3%). The plan must also label flow-direction arrows, low and high points, and the drainage easements carrying detention basins, water quality facilities, and storm sewer infrastructure, plus the top-of-wall and bottom-of-wall elevations at 20-foot intervals along retaining walls. Section 1-2712 carries the enforcement hook: before a certificate of occupancy issues, the applicant must submit as-built plans and an engineer's certification that the detention pond and water quality facilities were built to the approved drainage report, and the site must pass a County inspection confirming drainage improvements are installed as approved.
Violations & Fines
A project cannot receive a certificate of occupancy without submitting as-built drainage plans and an engineer's certification that detention ponds and water quality facilities match the approved report, per § 1-2712. If adverse weather blocks installation before a CO request, the county may issue a temporary certificate of occupancy only after the applicant posts security equal to 115% of the unfinished work's cost, and unfinished site improvements must be completed within six months.
Frequently Asked Questions
Is the drainage plan the same as the erosion-control plan in Douglas County?
How steep can graded slopes be on a Douglas County site plan?
Do retaining walls near a detention pond need special protection?
What must happen before a builder gets a certificate of occupancy?
Sources & Official References
Other rules in Douglas County
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