Green River/Duwamish

View the draft sections for the Green River/Duwamish GRP here: https://fortress.wa.gov/ecy/ezshare/sppr/preparedness/GreenRiverDuwamish_GRP_Jan2025/GRD_CoverPage.pdf

Description of the planning area

The Green River/Duwamish (including the Upper Green River) planning area starts in the headwaters of the Green River in the Cascade Mountains near Stampede Pass. The Howard A. Hanson Dam blocks the river’s flow and creates a reservoir 64 river miles upstream of where the river enters Puget Sound in Seattle at Elliott Bay. Below the Dam, the river flows through the steep rock cliffs of the Green River Gorge. Rural areas and suburban developments are present in the Green River Valley at the middle reach of the watershed. As the river continues toward Puget Sound, urban areas line the river.

The Green River becomes the Duwamish River at the former confluence with the Black River at Tukwila (near river mile 11). The planning area ends on the Duwamish River at river mile 6.5 near Cecil Moses Memorial Park on the left bank and North Wind’s Weir on the right bank. The remainder of the Duwamish River/Waterway, from the weir to the mouth at Elliott Bay in Seattle, is included in the Central Puget Sound GRP.  The planning area is within the Duwamish-Green Watershed or Water Resource Inventory Area (WRIA) 9.

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)