Environmental dredging residual generation and management

Abstract

The presence and magnitude of sediment contamination remaining in a completed dredge area can often dictate the success of an environmental dredging project. The need to better understand and manage this remaining contamination, referred to as "postdredging residuals," has increasingly been recognized by practitioners and investigators. Based on recent dredging projects with robust characterization programs, it is now understood that the residual contamination layer in the postdredging sediment comprises a mixture of contaminated sediments that originate from throughout the dredge cut. This mixture of contaminated sediments initially exhibits fluid mud properties that can contribute to sediment transport and contamination risk outside of the dredge area. This article reviews robust dredging residual evaluations recently performed in the United States and Canada, including the Hudson River, Lower Fox River, Ashtabula River, and Esquimalt Harbour, along with other projects. These data better inform the understanding of residuals generation, leading to improved models of dredging residual formation to inform remedy evaluation, selection, design, and implementation. Data from these projects confirm that the magnitude of dredging residuals is largely determined by site conditions, primarily in situ sediment fluidity or liquidity as measured by dry bulk density. While the generation of dredging residuals cannot be avoided, residuals can be successfully and efficiently managed through careful development and implementation of site-specific management plans. Integr Environ Assess Manag 2018;14:335-343. © 2018 The Authors. Integrated Environmental Assessment and Management Published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC).

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“…Dredging is a common technique for managing eutrophication problems [4], which aims to reduce the level of eutrophic substances and promote self-purification by removing silt and sediment from the bottom of water bodies. The purpose of environmental dredging is to reduce potential risks to human health and the environment; unfortunately, it remains unclear whether environmental dredging alone is effective in reducing such risks [5]. Moreover, dredging can have complex impacts on the ecosystems and environments of water bodies [6,7], mainly including factors, such as the resuspension of sediments due to dredging, release of pollutants from suspended sediments, residual substrate left behind by dredging, and long-term inputs of exogenous pollutants, which can have a great impact on the retention of N and P in sediments.…”

Effects of Dredging on Nitrogen and Phosphorus Storage Pat-Terns and Retention Mechanisms in Column Core Sediments in the Caohai Region of Dianchi Lake

“…Dredging is a common technique for managing eutrophication problems [5], which aims to reduce the level of eutrophic substances and promote self-purification by removing silt and sediment from the bottom of water bodies. The purpose of environmental dredging is to reduce potential risks to human health and the environment; unfortunately, it remains unclear whether environmental dredging alone is effective in reducing such risks [6]. Moreover, dredging can have complex impacts on the ecosystems and environments of water bodies [7,8], mainly including factors such as the re-suspension of sediments due to dredging, release of pollutants from suspended sediments, residual substrate left behind by dredging, and longterm inputs of exogenous pollutants, which can have a great impact on the retention of N and P in sediments.…”