Mountlake Terrace planning commission unanimously recommends 2026 Engineering Development Manual and code updates

The Mountlake Terrace Planning Commission voted unanimously Feb. 9 to recommend the City Council adopt the proposed 2026 Engineering Development Manual (EDM) and associated municipal code amendments following a staff presentation and an open-record hearing that drew no public testimony.

Planning staff said the revisions are intended to consolidate engineering development standards into the 2026 EDM, remove conflicting or outdated code sections and clarify technical requirements. Among the substantive changes staff described were a definition for accessory dwelling units (ADUs) for stormwater and capital facility billing, adjustments to permit thresholds, clarifications on overhead utility undergrounding, new rules for pavement cuts on recently constructed streets, revised driveway-approach width standards and a reduced local-access street cross section.

Planning staff noted that a single Equivalent Residential Unit (ERU) for stormwater billing is currently $28.94 per month and said "so an accessory dwelling unit would be half of that per month or about $14.15 dollars." Staff told the commission it proposes defining ADUs as one-half of an ERU for stormwater billing and capital facility charges.

Other technical changes staff highlighted included a permit exemption threshold that would allow up to 2,000 square feet of disturbance and 50 cubic yards of material movement without an engineering permit, redirecting plan-review and performance/maintenance bond provisions from specified code sections to the EDM or to consolidated code locations, and calling the 2026 EDM the adopted standard in chapter 19.95. The EDM language also clarifies when overhead utilities must be undergrounded and allows pavement cuts in recently constructed streets provided a 50-foot grinding overlay is performed in both directions.

On driveway standards, staff described a change that ties driveway-approach width to the number of on-site parking spaces and driveway length. Under the proposed wording, maximum approach widths would vary (for example, a property with five or fewer parking spaces and a driveway length of 100 feet or less would have a 12-foot maximum approach width) rather than a single fixed number. Staff said local-access streets would be revised from a 36-foot curb-to-curb standard to 32 feet, with the recorded right-of-way reduced from 60 feet to 56 feet.

Staff also described a three-year lookback for stormwater threshold verification, a terminology change from "sewer manhole" to "sewer maintenance hole," and several clerical updates, including replacing a retired stormwater contact, Laura Reed, with the presenter and Patrick Hutchins as the primary contacts.

The commission opened and immediately closed the public hearing after no members of the public signed up to testify in person, online or in writing. After brief discussion and a procedural clarification on motion wording (the item is titled "Engineering Development Manual" not "Engineering Design Manual"), a commissioner moved that the commission recommend City Council approve the EDM and the ordinances adopting the associated code amendments, including the technical revisions presented. The motion was seconded and carried on a unanimous voice vote.

The Planning Commission's recommendation will be forwarded to the City Council; staff said the commission's materials will be presented at a Council work session this week in advance of a scheduled open-record hearing at City Council on March 5.