Cleaning up: The slow slide into Swift Creek

Upper center: the Sumas Mountain Landslide

Mention “landslide” and it usually conjures an image of a sudden and violent collapse of a mountain slope or hillside. Insert “Sumas Mountain” before that word and residents of eastern Whatcom County will recognize a slow slide that for decades has clogged and flooded Swift Creek.

For many years the creek, which flows west to join the Sumas River, was dredged to manage the sediment and limit downstream flooding. But, several years ago, the 225-acre slide was found to contain naturally-occurring asbestos and metals – chromium, cobalt and nickel.

When the sediment dries, the asbestos can become airborne and present a risk to human health and the environment. The metals can affect plants on land and aquatic life.

An action plan

Sediment from the Sumas Mountain Landslide in Swift Creek

We’re excited to work with Whatcom County, which is receiving a total of $6.4 million in state funding to begin a series of projects to address these issues. We and the county have developed a legal agreement to guide the work that will receive this funding, consistent with the county’s 2012 Swift Creek Sediment Management Action Plan.

Dredge sediment

• Dredge Swift Creek as necessary before remedy starts.

Construct and repair levees

• Stabilize sediment piles.

• Use current sediment piles and deposits to construct new levees.

• Deposit any extra sediment not used in new construction in a repository and cover with clean soil.

• Repair, stabilize, and cap current levees with rock and clean soil.

Construct sedimentation basins and traps

• Capture new sediment in a series of traps and sedimentation basins.

Monitor, manage, and maintain

Another view of landslide sediment in Swift Creek

• Monitor surface water and air during construction and active sediment management.

• Monitor groundwater after stabilization.

• Manage new sediment in traps and basins by periodically removing and placing in the repository*.

*More sediment storage repositories will be needed. Repository site locations may change depending on property availability. We will amend the plan and prepare a supplemental Environmental Impact Statement (EIS) for future repositories.

• Inspect and repair facilities regularly.

• Dredge Swift Creek periodically as needed and place this sediment in the repository.

Control access

Restrict use of and access to the levees to prevent disturbance of, and exposure to, the sediment and airborne asbestos. Controls can include:

• Fencing off levees, sediment capture facilities, and storage basins.

• Placing legal restrictions on future use of the properties.

• Inspecting areas to ensure compliance.

• Purchasing additional property or easements may be required.

Public comments and community meeting

Before we adopt this plan, we’re asking the public to review it and related documents, and to send comments from Oct. 7 to Nov. 5, 2019.

We’re jointly hosting a public meeting with Whatcom County to provide information, answer questions and receive comments: 

• Wed., Oct. 9, 2019, 6-8 p.m. 
• Nooksack Valley Middle School, 404 West Columbia Street, Everson, Wash.

We have three documents up for review:

• Swift Creek Action Plan: describes the flood control and sediment management work to take place in the Swift Creek watershed.
• Consent Decree: the legal agreement between Whatcom County and Ecology under which the county will carry out the action plan.
• Public Participation Plan: explains how we and Whatcom County will keep people informed about the project and how people can provide input as it proceeds.

More information

• Comment online
• Whatcom County Swift Creek website 
• Ecology Swift Creek project website 

Our work with Whatcom County on this project is part of our investment in Washington communities. About 70 percent of our budget helps fund local government, tribal and non-profit projects that improve the environment, protect public safety and health, and benefit the economy.

By Larry Altose, communications manager, Northwest Regional Office