Stillaguamish River

Please note, we are making additional changes to the Stillaguamish River GRP maps. We are working to change the sectors within this planning area to better reflect the natural boundaries of the watershed. The updated maps will be included in the final version of this GRP.

The draft sections are available for comment until Dec. 21, 2025.

Description of the Planning Area

The Stillaguamish River GRP planning area resides entirely within Snohomish County and includes the city of Arlington. To the northwest, the planning area adjoins the Skagit River GRP planning area. The north and south borders are adjacent to the North Central Puget Sound GRP. The eastern boundary of the planning area is well within the river’s floodplain.

The STLGR-GRP planning area covers approximately 89 square miles in the northern part of Snohomish County. The entire Stillaguamish River Basin is approximately 700 square miles, with about 3,100 miles of streams. It is the fifth largest river basin draining into Puget Sound. Locals often shorten Stillaguamish and refer to the river as “The Stilly.”

What are Geographic Response Plans?

Geographic Response Plans (GRPs) are used to guide early response actions in the event of an oil spill. Ecology develops and updates GRPs in collaboration with state, local, and federal agencies and tribes. Each GRP is written for a specific area — for example, a river, a lake, or section of Puget Sound. Each GRP includes tactical response strategies tailored to a particular shore or waterway at risk of injury from oil.

GRPs have two main objectives:

• Identify sensitive natural, cultural, or significant economic resources at risk of injury from oil spills.
• Describe and prioritize response strategies in an effort to reduce injury to sensitive natural, cultural, and certain economic resources at risk from oil spills.

More information

• Learn more about GRPs
• See GRPs for the Northwest Area (Washington, Oregon, and Idaho)