Thin layer placement for marsh enhancement: Planning, design, construction, and monitoring considerations

Abstract

Thin layer placement (TLP) is the purposeful placement of thin layers of sediment in an environmentally acceptable manner to achieve a target elevation or thickness. TLP is used for a variety of purposes, such as sediment management, beneficial use of dredged material (DM), and ecological enhancement. The term “thin” is used to distinguish TLP from other methods of sediment placement in which sediments are applied in layers on the order of several meters thick. In this paper, DM disposal refers to the deposition of sediment in a location and manner where no beneficial use is attained; with DM placement the sediment is used to benefit society and the environment. The application of thin layers of sediment has advantages over more traditional, thicker sediment applications in environments where these thicker layers pose potential challenges to natural resources, infrastructure, navigation, or other assets. Although TLP projects are most often conducted in wetlands, there are open-water applications as well. But because TLP is relatively early in its development, there is a dearth of design and construction information and guidance available to practitioners. This paper provides a high-level summary of pending national TLP guidance being developed by the authors on behalf of the U.S. Army Corps of Engineers’ Engineer Research and Development Center (USACE ERDC).