Auburn staff propose square‑foot impact fee changes, ADU cap at 50% to comply with new state law

Auburn city staff told the City Council at its June 9 study session that the city must update both traffic and park impact fees this month to comply with two 2023 state laws aimed at supporting middle‑housing and accessory dwelling units (ADUs).

City Engineer and Assistant Director of Public Works Jacob Sweeting said the changes are required because “Senate Bill 5258 requires impact fees for housing to be variable based on square footage, number of bedrooms, or trips generated,” and “House Bill 1337 limits impact fees charged to ADUs to be no more than 50% of what would be charged to the principal residence.”

The changes are time‑sensitive because the laws must be reflected in fee schedules within six months of the city’s adoption of the comprehensive plans that address the affected infrastructure; Auburn adopted its parks and transportation comprehensive plan in December 2024, city staff said. Staff proposed using 1,700 square feet as the local “average” dwelling to scale fees up or down and to implement a per‑square‑foot traffic fee and a per‑square‑foot park fee so that smaller units pay proportionally less.

Staff described specifics. For traffic impact fees, Sweeting said the recommended structure charges by square foot instead of a flat per‑unit fee and would result in roughly $3.83 per square foot for single‑family detached homes outside the downtown reduced‑trip area; at the 1,700‑square‑foot baseline that equals the existing maximum of about $6,500. Accessory dwelling units would be charged at 50% of the principal unit’s obligation. Daniel Gaug, parks planning and development manager, showed the parks fee scale and said a 3,000‑square‑foot house would face an approximately $6,700 parks fee and an ADU about half that amount under the proposal.

Sweeting and Gaug told council they relied on regional American Community Survey data because the city’s permit tracking system only began recording residential square footage on June 1. Staff said they will collect local square‑footage data through 2025 and 2026 to refine fees later if needed. Sweeting said the proposed schedule “does not result in any increase” for any new unit compared with current rates.

Next steps: staff said a resolution to adopt the updated fee schedule will come back to council next week, and additional code cleanup for park impact fees will follow this summer.

Council members asked how ADU fees are assessed; staff said fees are due at permit issuance and “whoever applies for the permit essentially, is who pays those fees,” and fees are vested at the time of application. Councilors also asked about the data limits staff used and were told local tracking will improve in the coming year.

The council did not take a final vote at the study session; staff will return with an implementing resolution.