Issaquah committee backs guardrails to allow tree preservation, critical-area exceptions in street standards

The Issaquah City Council Mobility and Infrastructure Committee on Feb. 11 reviewed proposed guardrails for a deviation process to the city’s street standards that would let certain projects reduce or eliminate the five-foot landscape planter strip between curb and sidewalk.

The administration asked the committee whether it supports three elements: (1) using guardrails and a deviation process to preserve trees, protect critical areas, or maintain driveway access for properties not being redeveloped; (2) creating standards specifically for rehabilitation projects; and (3) creating standards for interim bicycle and pedestrian connections. John Mortensen, the city’s Transportation Engineering Manager, described the proposal and asked the committee for direction.

The committee broadly supported the administration’s proposed guardrails and asked staff to draft revisions to the street standards for further review in June and return to full council in third quarter. Chair Chris Ray summarized the committee direction as “proceed with the guardrails that have been outlined tonight and in the staff report,” and requested future reporting on how many deviations are applied and granted.

The guardrails proposed by staff center on three technical inputs: a pedestrian level of traffic stress (PLTS) performance target (the administration proposes PLTS of 2 or better), an ISA-certified arborist tree-health assessment when trees are proposed for preservation, and critical-areas reports to identify where impacts to streams or wetlands would preclude constructing the planter strip. Mortensen said the PLTS metric “comes from the WSDOT design manual,” an adopted standard the city uses, and described PLTS as a 1–4 performance score that factors lane count, volume and speed.

Mortensen showed examples where the five-foot planter strip creates conflicts: healthy, mature trees that would be lost if a planter is installed; sidewalks that would require relocating streams or wetlands; and existing driveways that would become steeper if the planter strip were added. He said the administration will treat the preservation of healthy trees as a priority and will prioritize native species while recognizing some nonnative trees may have community or historic value.

For driveway impacts, staff described the Northwest Sammamish Road nonmotorized project where the design team’s preferred alternative includes a narrower (three-foot) planter strip in places to avoid steepening existing driveways that serve properties not being redeveloped. Mortensen said the administration initially proposed a 12% maximum driveway slope threshold but will research accepted engineering standards and return with recommended numeric limits. He said when a property is being redeveloped, the property owner would be expected to address driveway grading as part of development.

On rehabilitation projects — defined as projects that extend the service life of an existing facility without changing street use — staff proposed a new project category to allow treatments such as overlays, retaining-wall repair, curb-ramp replacement, bridge repair, removal or protection of roadside obstacles, and other in‑kind repairs. Mortensen said WSDOT has existing guidance for rehabilitation projects and the city’s standards should acknowledge that rehabilitation differs from full reconstruction.

The Transportation Advisory Board reviewed the proposal on Dec. 4 and Jan. 22 and generally supported guardrails for tree preservation and critical-area protection, the PLTS target, meandering sidewalks to maximize planting area where feasible, and creating project types for rehabilitation and interim nonmotorized connections. Erica Boyd, a TAB member who attended the meeting, told the committee she was present as a liaison and resource and summarized TAB’s support.

Committee members asked staff to keep the deviation criteria clear and prescriptive so applicants and staff can consistently apply them once they are translated into street standards and Title 18 code language. Deputy Council President Barbara DeMichele suggested combining the tree-preservation language so it is clear arborist review will apply to all trees proposed for preservation, whether native or locally important nonnative species. Several council members asked that the city later track how often deviations are requested and granted to evaluate whether the standards are functioning as intended.

Next steps: staff will draft proposed edits to the street standards using the committee’s direction and return to the committee in June; follow-up code changes to Title 18 will be prepared by Community Planning and Development, and the administration plans to bring final revisions to full council in the third quarter. Mortensen said the revisions will include clearer written criteria, the arborist and critical-area report requirements, and a refined approach to driveway slope standards.