Public urges Council to protect trees as Seattle updates stormwater code

Dozens of residents and environmental advocates told the Seattle Governance & Utilities Committee on April 9 that proposed changes to the city's stormwater code risk weakening protections for trees and streamside habitat.

At the start of the morning's hybrid public-comment period, June told the committee: "Please require new and retained trees as stormwater management like other cities," arguing mature trees reduce runoff and protect ratepayers from higher infrastructure costs. Sandy of Tree Action Seattle asked the council to amend Council Bill 121190 to explicitly credit trees in stormwater calculations, saying "other Washington cities give credit for both retained trees and new trees." Ruth Williams, speaking on behalf of an "Alliance," urged maintaining lake and stream buffers and opposed raising the threshold for untreated runoff from 2,000 to 5,000 square feet.

The public comments centered on two technical changes that drew concern: whether the code credits trees when evaluating on-site stormwater benefits, and revisions to small-site flow-control requirements in parts of the city with constrained conveyance systems. Kevin Burrell, senior policy manager for Seattle Public Utilities (SPU), told the committee that trees are already among the tools the city considers for managing stormwater and that the draft code provides credit options for new and retained trees but does not require a single prescriptive solution. Burrell said some Ecology-driven changes also revise flow-control standards in small basins (including areas north of 85th Street around Haller Lake and Green Lake), where SPU staff concluded certain historic standards imposed costly small tanks with limited water-quality benefit.

Supporters of stronger tree protections argued the changes could accelerate canopy loss, hurt salmon habitat and increase stormwater costs. Several commenters asked the council to require that arborist data be used in stormwater calculations and to narrow exemptions for public-works and utility maintenance so those activities do not bypass runoff protections.

SPU staff said the 2026 update is primarily to comply with Washington Department of Ecology requirements and that the city received more than 550 written public comments during the code review. The department plans a follow-up memo and additional briefings before a committee vote; the proposed effective date for the update is July 1, 2026, with transition guidance for projects already in the permitting pipeline.

The committee did not take a final vote on the code update on April 9; staff said a memo with responses to public comments will be provided to members ahead of further committee consideration.