Beneficial Reuse of Dredge Spoils for a More Resilient Coast

Coastal communities continue to be at risk with sea levels rising. Along these coastal shorelines, vegetated marshes and ridges provide habitat for wildlife and resiliency against storm surge and erosion in low-lying areas. Often, spoils from maintenance dredging of harbors and rivers are placed in confined disposal sites (impoundments), providing little benefit to the environment. Reusing these spoils to restore low-lying marsh areas that are disappearing because of sea level rise, storm damage, sediment deficits, and other natural and manmade processes is growing trend. Design and construction using dredged sediments in a coastal environment can be challenging. It is critical to design and place fill in sensitive habitats in a controlled, thoughtful manner that enhances the environment. Low dikes are often used to contain fill, which is typically excavated and placed using a hydraulic dredge. These dikes are long linear features, often in a marsh environment, and can be difficult to construct. During construction, the project team (contractors and designers) must understand that these are controlled fill projects, with elevation targets and containment requirements. Distribution of sediments to meet project goals typically requires regular movement of the dredge outfall and monitoring during construction to prevent over-topping of containment dikes, and ensure sufficient fill has been placed to meet project objectives. Dredged sediments can be a renewable resource to restore coastal areas when used in projects that are designed and constructed correctly. In this paper, we will discuss design considerations, construction challenges and construction monitoring, including innovative instrumentation, that can help enhance the sustainability and resiliency of low-lying coastal communities.