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The Sumas Mountain landslide near the headwaters of Swift Creek in Whatcom County, Washington, releases up to 120,000 cubic yards of excess sediment into Swift Creek each year. The slide material contains deposits of naturally-occurring asbestos that can become exposed when water levels in the creek are low, when the creek is dredged, or when floods deposit material on banks and adjacent properties.

Asbestos can become airborne when this asbestos-containing sediment is disturbed. This could happen during activities like walking or riding on sediments, or if the sediments are used for home construction projects, such as driveways or pathways. When asbestos becomes airborne, it can be breathed into the lungs and increase the risk of developing asbestos-related disease.

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What Has Been Done to Clean Up the Site?

EPA is working with local, state, and federal agencies on a safe, long-term management plan for sediments coming from Sumas Mountain.

In July 2013, the Whatcom County Council approved an Environmental Impact Statement (EIS) for the Swift Creek sediment management plan. EPA incorporated a similar plan as one of the options evaluated in our Engineering Evaluation/Cost Analysis (EE/CA).

In an agreement signed in 2014, the EPA, Whatcom County and the Washington Department of Ecology formalized the commitments each can make towards implementation of the work in the EIS and EE/CA.

Sampling history

In 2006, EPA conducted "activity-based" air sampling to determine whether asbestos fibers in piles of dredged sediments along Swift Creek can get into a person's breathing zone during routine activities such as raking, shoveling, jogging, and biking. In February 2007, EPA released a Summary Report which showed elevated levels of risk for certain activities. As a result of these findings, EPA recommended that local residents limit their exposure to the dredged materials.

Following flooding in January 2009, EPA sampled water sediments and flood deposits along the Sumas River. The results confirm that elevated asbestos levels occur from Sumas Mountain to (and probably beyond) the Canadian border.

In August 2010, EPA conducted soil and activity-based sampling to provide data to determine the degree of potential risks to individuals who are exposed to airborne asbestos as a result of working or living in areas with flood deposits contaminated with asbestos.

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