Staff briefs committee on code updates to comply with Ecology’s 2024 Phase I stormwater permit; timeline extends into 2026

Planning and Development Services staff briefed the Snohomish County Planning and Community Development Committee on April 1 about proposed updates to county drainage and development rules to comply with the Washington Department of Ecology's 2024 Phase I Municipal Stormwater Permit (NPDES).

Sarah Hickam, PDS, said code amendments, drainage‑manual updates and changes to engineering design and development standards (EDDS) are needed for consistency with Ecology's permit. "I will focus today on just the code," Hickam said, noting the drainage manual and EDDS are administrative rules while code changes are legislative and will come to the council for adoption.

Hickam told the committee Ecology identified seven significant changes that require updates to the county's enforceable documents. Staff said the primary code changes will occur in SCC chapters 30.63A and 30.63B and that the code amendments generally narrow the scope of exemptions, which will likely increase the number of permits required for redevelopment and some pavement projects.

Key examples staff described include changes to redevelopment thresholds so that replaced hard surfaces count toward the 5,000-square-foot trigger for applicability of Minimum Requirements (MRs) 1–9; for commercial/industrial redevelopment, an additional threshold would count replacement costs of hard surfaces if they total 50% or more of existing surfaces on-site. Staff said pavement‑maintenance exemptions would be narrowed to only the areas necessarily disturbed to repair or maintain pavement, and that utilities would be exempt only for trench work required for underground repair, maintenance or upgrades. Hickam said the proposed definition updates also include a new vehicular‑use definition that airports helped develop so airport runways would be treated as vehicular use.

Hickam described a shift in the drainage manual toward pollutant‑specific treatment performance goals rather than generic water‑quality treatment, and said the drainage manual will add requirements for testing and remediation related to building materials containing PCBs for certain older structures; staff and Ecology will refine those details during the rule‑making and public engagement phases.

Staff outlined a schedule: staff will prepare two tables for Ecology — one documenting how the county incorporated Ecology's seven significant changes and another listing other substantive changes — and then brief the Planning Commission in May. PDS will provide an ECAF and draft materials to the council for Ecology's July 1, 2025 submittal of preliminary drafts. Ecology will review the drafts through about December 2025, after which the county anticipates broader public engagement, ordinance drafting, and final council consideration in mid‑2026. Hickam said staff hopes to present code adoption materials to the council in June 2026 and make a final submittal to Ecology in July 2026.

Committee members asked whether the critical areas update would affect the timeline. Hickam said the two projects run in parallel and that critical‑areas changes could result in minor changes to the drainage‑code chapters; she did not expect the critical‑areas update to prevent the county from meeting the July 1 submission to Ecology. Members also asked about outreach and whether developers and contractors are aware that work previously exempt may require new permits; Hickam said staff will engage the public and permitting staff to raise awareness before code changes take effect in 2026.

Eric Blankenship from SWIM was online and available for technical questions, staff said. The committee received the briefing and did not take final action at the meeting.