Mill Creek adopts updates to Critical Areas Ordinance, including Riparian Management Zones (RMZs) and buffer revisions
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Summary
The council voted 6-0 to adopt comprehensive amendments to the city's Critical Areas Ordinance, aligning local rules with state best-available science, updating wetland buffers, adopting Riparian Management Zones tied to tree height, and clarifying mitigation and hazard-tree procedures.
The Mill Creek City Council unanimously adopted an ordinance Jan. 6 that amends the city’s Critical Areas Ordinance (CAM chapter references in the packet: Mill Creek Municipal Code chapters 17.32 and 18.06) to align local regulations with more recent state guidance and best-available science.
Planner staff and consultants explained several substantive changes: clearer rules for nonconforming uses and structures; adjustments to trails and mitigation requirements; an updated wetland-buffer table driven by wetland category and habitat scores; clarified mitigation-priority sequencing; monitoring requirements for compensatory mitigation; and a new definition and process for hazard trees. The staff presentation emphasized use of Ecology, the Department of Fish and Wildlife, and DNR recommendations as the primary science sources.
One of the more consequential technical changes shifts stream-side protections from fixed buffers to Riparian Management Zones (RMZs). RMZ widths will be calculated using the average maximum height of dominant trees on a site, subject to a 100-foot minimum; staff showed a city map estimating RMZ widths and said the method will increase protections for about eight miles of stream and reduce widths on approximately two miles. Staff also noted property owners may commission their own stamped biological analyses if they dispute the city’s map-based tree-height data; critical-area reports are valid for five years unless extended by the director.
Council asked questions about hazard-tree reports, enforcement consequences for unauthorized tree removal (staff cited a potential $1,000-per-tree penalty and standard code-enforcement procedures), and how private analyses would be reconciled with the city’s mapping. Staff said WDFW provided a letter of support on the draft and DNR and Commerce offered technical comments that staff incorporated.
Following public testimony (no in-room speakers signed up for this hearing) and brief council discussion, the council moved and approved the ordinance to adopt the CAO amendments by a 6-0 vote.
