Swift Creek resides in the northeastern lowlands of Whatcom County in Washington state. Over several decades, a slow-moving landslide on Sumas Mountain has carried sediments containing naturally occurring asbestos and metals into the creek bed. The landslide encompasses approximately 225 acres, weighing in at an estimated 68 million cubic tons. The sediment from this landslide threatens the surrounding habitat, while also creating a public health risk as dry weather turns asbestos-filled sediments into dust. Dredging and sediment management were utilized for years to mitigate downstream flooding, resulting in liability under the Model Toxic Control Act.
With this, the Washington State Department of Ecology and Whatcom County have joined together to create the Swift Creek Action Plan. This plan aims to address these liabilities while also reducing environmental and human health risks resulting from the landslide. Seeing that the landslide cannot be stopped, the goal of this project is to slow the streamflow of Swift Creek, allowing sediment to settle out of the water in the creek’s upper reaches. This will allow Whatcom County to collect, cover, and store the sediment in long-term repositories, managing the asbestos containing dust, while also reducing flooding.
Herrera’s team of regional experts are assisting Whatcom County in advancing repository development and design of instream priority actions, sediment basins, as well as debris deflection and setback levees identified in the Swift Creek Sediment Management Plan. Throughout this project, Herrera will support the DSEIS and develop preliminary design analysis for the proposed repository sites located on the Swift Creek alluvial fan east of Goodwin Road. More information on this project can be discovered here.