Contact Information:

Department of Community Development
6300 Southcenter Blvd., #100
Tukwila, WA 98188

Phone: 206 431-3670
Fax: 206 431-3665

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Wetlands, Streams and Steep Slopes Code Update

Planning Commission has finalized their recommendation to the City Council on the proposed Critical Areas Code. The Community Development and Neighborhoods Committee will be reviewing the Planning Commission’s recommended draft on September 10, 2019. Here is the link to the Committee packet.

The City Council will held a public hearing on September 23, 2019. Here is the link to the Council packet 

Additionally, a SEPA Determination has been issued on the Planning Commission recommended draft. Here is the link to the SEPA Determination.

Following are links to the staff reports prepared for the Planning Commission meetings on this topic: 

June 27, 2019 Planning Commission meeting.

May 23, 2019 Planning Commission meeting. 

April 11, 2019 Planning Commission meeting.

February 28, 2019 Planning Commission meeting.

November 8, 2018 Planning Commission meeting.

The Community Affairs and Parks Committee was briefed about the update process on June 26, 2018.

To get on the interested party list: 

Contact Tukwila Planning Department, at, 206-431-3685. 


The City adopted Environmentally Sensitive Area regulations in 2010: Chapter 18.45 Tukwila Zoning Code as required under the Growth Management Act (GMA) using the standards of Best Available Science.  

Since then the Department of Ecology established new guidance on Best Available Science for wetlandsand the Department of Fish and Wildlife established new guidance on Best Available Science for streams .  

The City’s consultant, The Watershed Company, prepared a Gap Analysis Report which will be used to draft the new rules. This document provides a review of the City’s existing regulations, noting gaps where existing regulations may not be consistent with Best Available Science.


What is best available science?

Best available science or BAS is the most current science relative to the functions and values of the critical areas, including the role of buffers in protecting wetland and stream functions and fish and wildlife. Under the GMA (RCW 36.70a.175), best available science must be used to designate and protect critical areas and to take measures to preserve and enhance anadromous fisheries, such as salmon (fish born in fresh water and spends most of its life in the salt water and return to fresh water to spawn).

What are wetlands and what is their importance?

“Wetland” means those areas that are inundated or saturated by groundwater or surface water at a frequency and duration sufficient to support, and that under normal circumstances do support, a prevalence of vegetation typically adapted for life in saturated soil conditions. Wetlands generally include bogs, swamps, marshes, ponds, lakes and similar areas.  

Wetlands do not include those artificial wetlands intentionally created from nonwetland sites, including but not limited to irrigation and drainage ditches, grass-lined swales, canals, detention facilities, wastewater treatment facilities, farm ponds, landscape amenities or those wetlands created after July 1, 1990 that were unintentionally created as a result of the construction of a road, street or highway. However, those artificial wetlands intentionally created from non-wetland areas to mitigate conversion of wetlands as permitted by the City shall be considered wetlands. 

Wetlands and their associated buffers are important in that they help maintain water quality; store and convey storm and flood water; recharge ground water; provide fish and wildlife habitat; and serve as areas for recreation, education, scientific study and aesthetic appreciation.

What are streams and what is their importance?

“Watercourse” means a course or route formed by nature or modified by man, generally consisting of a channel with a bed and banks or sides substantially throughout its length along which surface water flows naturally, including the Green/Duwamish River. The channel or bed need not contain water year-round. Watercourses do not include irrigation ditches, stormwater runoff channels or devices, or other entirely artificial watercourses unless they are used by salmonids or to convey or pass through stream flows naturally occurring prior to construction of such devices.  

Streams and their associated buffers are important in that they provide important fish and wildlife habitat and travel corridors; help maintain water quality; store and convey storm and flood water; recharge groundwater; and serve as areas for recreation, education, scientific study and aesthetic appreciation.


Current Tukwila Municipal Code Chapter 18.45 Environmentally Sensitive Areas Code

Find your property on the City’s Map. 

City of Tukwila contact:, 206-431-3685.

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