INVESTIGATION OF THE SUMAS MOUNTAIN LANDSLIDE AREA: A CASE STUDY OF A EPA'S FRAMEWORK APPLIED TO A NATURALLY OCCURRING ASBESTOS SITE

The Sumas Mountain Landslide is an active landslide in the Cascade Mountain Range in the Pacific Northwest, Washington State, United States. The slide contains elevated concentrations of chrysotile asbestos and this material is being deposited into Swift Creek and the Sumas River. Approximately 150,000 cubic yards of material moves into the creek annually and this is expected to continue for the next 400 – 600 years. Over the past several decades, portions of Swift Creek were dredged to prevent flooding of roads and adjacent agricultural land. During this time, dredged materials were removed by private interests and landowners for use as fill material in construction projects, road bed material, and other purposes. EPA used the draft Framework for Investigation of Asbestos-Contaminated Superfund Sites to support the investigation approach used at the site. Based on initial sampling of the dredged materials by PLM and opportunistic sampling of personnel in the field, EPA proceeded to activity-based sampling in the vicinity of Swift Creek. Based on these results, EPA restricted the practice of removing dredged materials as has been done in the past because of concerns about exposures to asbestos in this material. Flooding in January 2009 resulted in large quantities of sediment to be deposited onto upland areas, including residential properties and farm land. This flooding occurred not just in Swift Creek but further downstream in the Sumas River. Sampling of this upland soil (maximum of 33%), bank sediment (maximum of 23%), and surface water (maximum of 879 MFL) in May 2009 indicated chrysotile concentrations that were much higher than anticipated. This talk will focus on the framework for EPA’s site investigation efforts, the recent sampling results, and planned next steps for this extremely complex situation. EPA is working cooperatively with the local residents, Whatcom County, and other stakeholders to look for creative solutions to managing the large volume of asbestos-laden material that flows into this system annually.