Englewood updates storm drainage manual, adopts MS4 exclusions and clarifies submission rules

Englewood public works staff presented proposed revisions to the Storm Drainage Criteria Manual and related city code, and the Water and Sewer Board recommended the updates for City Council consideration.

Tyler Gellis, stormwater program manager in Public Works, said the manual — last substantially revised in 2020 after extreme 2018 storm events — determines city stormwater requirements for construction and post‑construction work. Staff and a consultant performed a cleanup and clarified several thresholds, submittal requirements and exemptions required by the state Municipal Separate Storm Sewer (MS4) permit.

Key proposed changes include: - Submittal timing and scope: allow demolition‑only projects to obtain grading permits without a full drainage report and post‑construction stormwater quality plan, provided those documents are submitted before building permits or construction; add a 30‑day staff review window for plan submissions. - Construction (stormwater management plans): align thresholds by lowering the land‑disturbance trigger for a construction stormwater management plan from 10,000 square feet to 5,000 square feet (and require a grading permit at that threshold) to remove a discrepancy in the manual. - Post‑construction (permanent stormwater quality): adopt exclusions referenced in the state MS4 permit for certain low‑impact project types so projects that meet the state criteria would be exempt locally from detention and some post‑construction quality requirements. Examples staff highlighted: roadway mill‑and‑overlay or pavement management work, some roadway rebuilds that do not increase runoff, above‑ or below‑ground utility trenching that is restored to the prior condition, and many shared‑use trails where impervious area is minimal. - As‑builts and digital records: require as‑built (record) drawings before terminating a grading permit, and require GIS and AutoCAD files to improve digital tracking of storm facilities and easements. - Code change for low‑risk discharges: amend city code section 12‑5‑9 (illicit discharge detection and elimination) to allow discharges that conform to the Colorado Department of Public Health and Environment (CDPHE) low‑risk discharge policy guidance, such as surface cosmetic pressure‑washing runoff to land and low‑impact trail runoff, so the city can apply evolving state guidance without frequent code changes.

Gellis said many of the edits were clarifications and readability fixes requested by developers and the public; staff emphasized that several changes are necessary to be able to use state‑allowed exemptions locally under the MS4 permit. The board voted to recommend the proposed revisions to council.

Gellis said the changes are intended to align the manual with state permit language, improve clarity for applicants, reduce paper submittal backlog and provide predictable review timelines. Staff plans a public stormwater town hall on Aug. 5 and to publish a tracked‑changes version of the manual for review.