City updates engineering design standards to reflect state housing and transportation laws

Jacob Sweeting, assistant director of public works and city engineer, briefed council on proposed revisions to Auburn’s Engineering Design and Construction Standards (EDS) at the Jan. 27 study session.

Sweeting said the revisions respond to newly enacted state laws and recent city policy updates. He told council the standards will be updated to reflect House Bill 1110 (middle housing), House Bill 1181 (multimodal and environmental elements in transportation planning), the 2025 Washington State Department of Transportation standard specifications and the 2024 Department of Ecology stormwater manual.

Among notable changes Sweeting described: - Revisions tied to HB 1110 to avoid design standards that unduly burden middle‑housing types (ADUs, duplexes, triplexes, quadplexes, cottage housing). For example, alley‑paving exemptions that previously referred to single‑family projects would change to a vehicle‑trip threshold (20 vehicles per day) so duplexes/ADUs are not treated more strictly than single‑family homes. - Adjusted shared‑access (shared driveway) standards to increase easement width (to 31 feet) and require sidewalks on sides where access is taken, to accommodate possible future middle‑housing infill while preserving exceptions for existing lots where physical constraints apply. - Updates to typical roadway cross sections and bike‑facility guidance to reflect the city’s 2024 comprehensive transportation plan, including buffered bike lanes and allowance for separated trails where the plan identifies them. Lane widths on arterials were reduced from 14 to 12 feet in typical sections (except on designated truck routes) and industrial lane widths were reduced to encourage lower speeds where appropriate. - Minor grading permit criteria were loosened and expanded to commercial and industrial properties to streamline permitting for common re‑paving or grading work.

Council members asked about the evidence supporting lane‑width changes and truck routing. Sweeting said the changes reflect Federal Highway Administration, state DOT and peer‑jurisdiction guidance and form part of the city’s comprehensive safety action plan; he added that truck routes and wider lanes will remain where needed.

Why it matters: The revisions implement state housing law and reflect recent city transportation policy, changing how future infill and street projects will be designed and what exceptions apply.

Sweeting said the city plans to publish the updated standards within weeks and will continue to accept technical questions and provide guidance to permit applicants. No final adoption occurred at the study session; the revision process continues.