22 May 2023

Advances in Dredged Material Evaluations for Inland and Ocean Aquatic Placement: Modernized Processes and Supportive Tools

Abstract: As part of the US Army Corps of Engineers’ mission to evaluate and move dredged material (DM) to maintain navigation channels, environmental evaluation of the prospective material is required by the Code of Federal Regulations. While existing guidance manuals provide useful guidance to DM regulators, they are over 30 years old and not reflective of the latest science. However, efforts to update procedures and publish the documents individually or as a combined dredging manual have been thus far unsuccessful. These issues, coupled with a lack of consistent reporting and decision documentation, lead to delays arising from challenges addressing project-specific issues not clearly covered within the existing guidance, revisiting previously resolved issues or negotiating disputes between permitting authorities. This technical report provides a path toward modernization of the environmental compliance aspects of DM evaluation guidance in part through software executables guiding the management and decision process and through a structured, evidence-based approach. The value added is an updated approach to DM testing and evaluation decisions.

24 Jan 2023

Swan Island Resilience Model Development; Phase I: Conceptual Model

Abstract: This report documents the development of an integrated hydrodynamic and ecological model to test assumptions about island resilience. Swan Island, a 25-acre island in Chesapeake Bay, Maryland, was used as a case study. An interagency, interdisciplinary team of scientists and engineers came together in a series of workshops to develop a simplified resilience model to examine the ability of islands to reduce waves and erosion and the impacts to nearby habitats and shorelines. This report describes the model development process and the results from this first key step: model conceptualization. The final conceptual model identifies four main components: vegetative biomass, island elevation, waves/currents, and sediment supply. These components interact to form and support specific habitat types occurring on the island: coastal dunes, high marsh, low marsh, and submerged aquatic vegetation. The pre-and post-construction field data, coupled with hydrodynamic ecological models, will provide predictive capabilities of island resilience and evaluations of accrued benefits for future island creation and restoration projects. The process and methods described can be applied to island projects in a variety of regions and geographic scales.

1 Dec 2022

A Review of Tidal Embayment Shoaling Mechanisms in the Context of Future Wetland Placement

Abstract: Wetland construction in tidally influenced embayments is a strategy for beneficial use of sediment dredged from nearby navigation channels. These projects have the potential to alter basin morphology, tidal hydrodynamics, and shoaling trends. This special report provides a broad review of the literature related to engineering-induced changes in tidal range, salinity, tidal prism, tidal asymmetry, and other known causes of shoaling. Each potential shoaling mechanism is then evaluated in the context of wetland placement to provide a foundation for future beneficial use research. Based on a compilation of worldwide examples, wetland placement may reduce tidal amplitude and enhance ebb current dominance, thus reducing shoaling rates in the channels. However, constructed wetlands could also reduce the embayment’s tidal prism and cause accelerated shoaling relative to the pre-engineered rate. Because constructed wetlands are often created in conjunction with navigation channel dredging, the system’s morphologic response to wetland construction is likely to be superimposed upon its response to channel deepening, and the net effect may vary depending on a variety of system- specific parameters. Planning for future wetland placements should include an evaluation of local hydrodynamic behavior considering these factors to predict site-specific response.

19 Sep 2022

Systematic Beneficial Use of Dredged Sediments: Matching Sediment Needs with Dredging Requirements

PURPOSE: This technical note (TN) will outline a framework to identify beneficial and cost-effective coastal beneficial use of dredged sediment (BUDS) projects. Creation of a BUDS framework that can be applied at scale will promote sustainable BUDS practices, facilitating the delivery of flood risk management, social, and environmental benefits while still fulfilling the US Army Corps of Engineers (USACE) navigation mission. This proactive forecasting approach uses multi-criteria decision analysis (MCDA) and optimization tools to balance tradeoffs between navigation dredging and BUDS goals over project-scale timespans. The proposed framework utilizes available tools to quantify ecological system evolution and current and future dredging needs to develop a systems-level approach to BUDS. Required data include current and future information on (1) existing and planned natural and created aquatic ecological systems, which may include natural and nature-based features (NNBFs), (2) dredging requirements and costs, and (3) aquatic system physical and environmental data.

12 Sep 2022

Application of Clean Dredged Material to Facilitate Contaminated Sediment Source Control

Abstract: Navigation channels, turning basins, and other US Army Corps of Engineers (USACE)–managed navigation infrastructure often serve as repositories for contaminated sediment from off-site sources. As much as 10% of the material that USACE dredges on an annual basis is contaminated such that it requires additional and more costly management (for example, rehandling and placement in managed confined disposal facilities). Presence of contaminated sediments constrain potential management options resulting in additional costs and opportunity loss from the inability to beneficially use the material. One potential solution is applying clean dredged material to stabilize and isolate contaminated sediment sources, preventing further transport and introduction to USACE-managed infrastructure. This document summarizes a comprehensive literature review of laboratory and field case studies relevant to using clean dredged material to isolate or stabilize contaminated sediments, focusing on the physical, chemical, and biological parameters critical to establishing its feasibility and long-term effectiveness. Potentially effective engineering control measures were also reviewed where erosion and site hydrodynamics are facilitating the transport of contaminated sediments to USACE-maintained navigation infrastructure. This literature review documents and summarizes those factors considered in establishing feasibility and long-term effectiveness of the approach as well as the applicable engineering tools employed and constraints encountered.

31 Aug 2022

Current State of Practice of Nearshore Nourishment by the United States Army Corps of Engineers

Abstract: This US Army Corps of Engineers (USACE) special report prepared by the US Army Engineer Research and Development Center, Coastal and Hydraulics Laboratory, provides an overview of the current state of practice for nearshore nourishment with dredged sediment. This special report was completed with responses and input from professionals across the dredging and placement teams from each of the USACE Coastal and Great Lakes districts, providing comprehensive overviews of the decision trees these districts utilize in the placement of their dredged sediment. This report describes the general practice of nearshore nourishment, the impediments and concerns faced by nearshore nourishment projects, and the practical methods utilized by the Coastal and Great Lakes districts for their nearshore nourishment projects. Understanding the current state of practice, along with the general and specific impediments the districts face, enables further research in and development of best practices for use across the USACE and better communication of the practice to other stakeholders.

30 Aug 2022

Screening Dredged Material to Meet Placement Requirements

Abstract: Certain types of dredging projects require screening of the dredged material (DM) to achieve the project’s DM placement requirement(s). Screening in the context of this report will be defined as the separation of an oversized fraction of the DM from the remaining fraction to meet project-specific placement compliance criteria (or criterion). Examples of DM placement requirements include aspects such as removing Munitions and Explosives of Concern (MEC) to address safety concerns and extracting over-sized material for beneficial use of DM (e.g., gravel and debris from sand to meet beach nourishment placement standards). Welp et al. (2008) provide detailed guidance for personnel involved in dredging projects with sediment containing MEC. The purpose of this document is to not only update the previous MEC-centric guidance with newly developed or identified technology but to also expand upon screening aspects to provide guidance for personnel involved in dredging projects that require removal of an oversized fraction for screening purposes other than just MEC removal.

12 Aug 2022

Swan Island: Monitoring and Adaptive Management Plan

Abstract: Swan Island is a 10.12 ha island located in the Maryland waters of the Chesapeake Bay. Because of its value as a natural wave break for the town of Ewell on nearby Smith Island, as well as the ongoing erosion and subsidence of the island, in 2019 US Army Corps of Engineers (USACE)–Baltimore District placed 45,873 m³ of dredged sediment and planted 200,000 marsh plants. This restoration provided an opportunity to quantify the engineering (that is, resilience) and ecological performance of the island, postplacement. The lack of quantitative data on the performance of natural features such as islands has led to perceived uncertainties that are often cited as barriers to implementation. To address these data gaps, a multidisciplinary collaboration of five government entities identified project objectives and monitoring parameters through a series of mediated workshops and then developed a conceptual model to articulate those parameters and the linkages between them. This monitoring and adaptive management plan (MAMP) documents those monitoring parameters and procedures and can serve as an example for other scales, regions, and research questions. Documenting research and monitoring efforts may help to foster widespread acceptance of nature-based solutions such as islands.

11 Aug 2022

Environmental Evaluation and Management of Dredged Material for Beneficial Use: A Regional Beneficial Use Testing Manual for the Great Lakes

Abstract: The Environmental Evaluation and Management of Dredged Material for Beneficial Use: A Regional Beneficial Use Testing Manual for the Great Lakes (a.k.a. Great Lakes Beneficial Use Testing Manual) is a resource document providing technical guidance for evaluating the suitability of dredged sediment for beneficial use in aquatic and terrestrial environments in the Great Lakes region. The procedures in this manual are based on the Environmental Laboratory extensive research, working with US Army Corps of Engineers (USACE) Great Lakes districts, state resource agencies, and local stakeholders seeking to develop dredged material beneficial use alternatives consistent with regional needs and goals. This manual is the first guidance document developed by USACE for evaluating the environmental suitability of dredged material specifically for beneficial use placements. It provides a tiered framework for evaluating the environmental suitability of aquatic and upland beneficial uses consistent with the Inland Testing Manual and the Upland Testing Manual. This manual is intended to serve as a regional platform to increase collaborative problem-solving and endorse a common understanding of the scientific and institutional practices for evaluating dredged material for any beneficial use. Dredged sediment may be managed as a valuable resource, with great potential to create economic, environmental, and social benefits.

4 Aug 2022

Supporting Bank and Near-bank Stabilization and Habitat Using Dredged Sediment: Documenting Best Practices

Abstract: In-water beneficial use of dredged sediment provides the US Army Corps of Engineers (USACE) the opportunity to increase beneficial use while controlling costs. Beneficial use projects in riverine environments include bank and near-bank placement, where sediments can protect against bank erosion and support habitat diversity. While bank and near-bank placement of navigation dredged sediment to support river-bank stabilization and habitat is currently practiced, documented examples are sparse. Documenting successful projects can support advancing the practice across USACE. In addition, documentation identifies data gaps required to develop engineering and ecosystem restoration guidance using navigation-dredged sediment. This report documents five USACE and international case studies that successfully applied these practices: Ephemeral Island Creation on the Upper Mississippi River; Gravel Island Creation on the Danube River; Gravel Bar Creation on the Tombigbee River; Wetland Habitat Restoration on the Sacramento-San Joaquin River Delta; and Island and Wetland Creation on the Lower Columbia River Estuary. Increased bank and near-bank placement can have multiple benefits, including reduced dredge volumes that would otherwise increase as banks erode, improved sustainable dredged sediment management strategies, expanded ecosystem restoration opportunities, and improved flood risk management. Data collected from site monitoring can be applied to support development of USACE engineering and ecosystem restoration guidance.