15 Apr 2024

Development and Testing of the Sediment Distribution Pipe (SDP): A Pragmatic Tool for Wetland Nourishment

Abstract: Standard dredging operations during thin layer placement (TLP) projects are labor intensive as crews are necessary to periodically move the outfall location, which can have lasting adverse effects on the marsh surface. In an effort to increase efficiency during TLP, a novel Sediment Distribution Pipe (SDP) system was investigated. This system offers multiple discharge points along the pipeline to increase the sediment distribution while reducing pipeline movements. An SDP Modeling Application (SDPMA) was developed to assist in the design of SDP field applications by quickly assessing the pressure and velocity inside the discharge pipe and approximating the slurry throw distances. An SDP field proof of concept was performed during a two-phase TLP on Sturgeon Island, New Jersey, in 2020. The SDPMA was shown to be an accurate method of predicting performance of the SDP. The SDP was successful at distributing dredge material across the placement site; however, further research is warranted to better quantify performance metrics.

21 Mar 2024

Pilot Project Using Tickler Chains in Lieu of Deflectors at Fire Island Inlet to Moriches Inlet, New York, Borrow Sites

Abstract: Risk for incidental take of sea turtles and sturgeon exists during hopper dredging operations throughout turtle and sturgeon habitats. Since 1992, draghead deflectors have been the main engineering tool used to minimize incidental hopper dredging takes of sea turtles and are also thought to reduce the chance of sturgeon impingement entrainment. Although reduced, turtle takes still happen annually, and the draghead deflectors reduce dredging productivity, increase fuel usage, and increase costs of operations. As such, there remains a need to research alternative turtle avoidance measures. The non-US dredging industry has used various versions of an engineering control called tickler chains (TC) in lieu of deflectors. If effective, TC could lower dredging costs and increase production in comparison to deflectors. This technical report describes a pilot study where TC were used in lieu of deflectors at Fire Island Inlet, New Y0rk. To the authors’ knowledge, this is the first time since the early 1990s that hopper-dredging has occurred without draghead deflectors along the east coast. No takes were recorded during the pilot study; however, no research was done to determine if sea turtles or sturgeon interacted with the TC. Recommendations for future TC research is provided in this technical report.

21 Mar 2024

A Beneficial Placement Decision Support Framework for Wetlands: Case Study for Mobile Harbor, USA

Abstract: The US Army Corps of Engineers, in the responsibility of maintaining navigational infrastructure, has a unique opportunity to improve coastal wetland resiliency and conserve coastal natural infrastructure through the beneficial use of dredged material for wetland restoration. Opportunities are widespread, and tools such as biophysical models can aid coastal managers in assessing habitat vulnerability and planning restoration. In this study, the Marsh Equilibrium Model was utilized in concert with observed data to predict future conditions and evaluate potential effects of beneficial use of dredged material to restore marshes in Mobile Harbor, Alabama. A range of site conditions and two restoration strategies were considered, and the subsequent impact to dredged material management area volumes evaluated. Results showed that wetland restoration via the thin-layer placement of dredged material can restore marsh elevation to combat sea level rise and conserve fill capacity at dredged material management areas. This approach is demonstrated for adoption nationwide by coastal managers.

29 Feb 2024

Hurdles to Beneficial Use of Dredged Material: Root Cause Analysis

Purpose: This technical note (TN) summarizes high points of an internal review of US Army Corps of Engineers (USACE) dredging and dredged material management practices, specifically beneficial use of dredged material (BUDM), that USACE manages from various navigation channels and ports around the nation.

14 Feb 2024

Hydraulic Sorting of Dredged Sediment in a Pipeline: An Evaluation of the Sediment Distribution Pipe

Abstract: The US Army Corps of Engineers (USACE) recently established a goal to beneficially use 70% of material dredged from the nation’s navigable waterways by the year 2030. Most of the sediments dredged by the USACE are heterogeneous mixtures of mud and sand, which can limit beneficial use of dredged material (BUDM) applications. Innovative technologies that can sort material during the dredging process are needed to help increase BUDM practices. This investigation sought to evaluate the ability of a sediment distribution pipe (SDP) to sort particles during transport in a pipeline. Field demonstrations were conducted during dredged material placements at Sturgeon Island, New Jersey. Velocity within the pipeline was found to be inadequate for efficient hydraulic sorting of fines (<75 μm) and produced inconclusive results. Small scale laboratory SDP experiments found that effluent from the SDP holes had an altered sediment texture compared to the initial slurry and that hydraulic sorting was occurring within the pipeline. However, outflow from the SDP holes was inconsistent, and typically >90% of the sediment mass was discharged out the end of the pipeline. Sorting efficiency of the SDP could not be accurately assessed in the current experimental configuration.

15 Dec 2023

Ranking Ports by Vessel Demand for Depth

Abstract: The US Army Corps of Engineers (USACE) traditionally uses two metrics to evaluate the maintenance of coastal navigation projects: tonnage at the associated port (representing relative importance) and the controlling depth in the channel (representing operating condition). These are incorporated into a risk-based decision framework directing funds where channel conditions have deteriorated and the disrupted tonnage potential is the highest. However, these metrics fail to capture shipper demand for the maintained depth service provided by the USACE through dredging. Using automatic identification system (AIS) data, the USACE is pioneering new metrics describing vessel demand for the channel depth, represented by vessel encroachment volume (VEV). VEV describes the volume of the hull intruding into a specified clearance margin above the bed and captures how much vessels use the deepest portions of USACE-dredged channels. This study compares the VEV among 13 ports over 4 years by combining AIS, tidal elevations, channel surveys, and sailing draft. The ports are ranked based on the services demanded by their user base to inform the decision framework driving dredge funding allocations. Integrating demand for-depth metrics into the Harbor Maintenance Fee assessment and/or Trust Fund disbursements could alleviate the constitutionality concerns and several criticisms levied against Harbor Maintenance funding.

31 Oct 2023

Proceedings from the Basin Sediment Management for Unique Island Topography Workshop, Mayagüez, Puerto Rico

Abstract: This report summarizes the Basin Sediment Management for Unique Island Topography Workshop hosted in-person and virtually at the University of Puerto Rico Mayagüez (UPRM) Department of Civil Engineering and Surveying, Mayagüez, Puerto Rico on 11 March 2022. The workshop was attended by approximately 80 federal, state, local, and academic organizations participants. It focused on Engineering With Nature® (EWN®), green infrastructure (GI) and low impact development (LID) opportunities for unique tropical island topography and included seven presentations from subject matter experts, a discussion on limitations and problems with prior projects, and two concurrent breakout sessions. Preworkshop activities included a field trip to multiple sites in the Añasco watershed conducted 09 March 2022, which served as a base case for the workshop. The field trip provided participants a unique perspective of the island’s topography and post 2017 Hurricane María issues and impacts. During the breakout sessions, participants identified new project opportunities for EWN®-GI and LID at two selected sites from the field trip. Each group developed alternatives for their chosen site and identified concepts that could turn into great opportunities for the surrounding communities and significantly benefit the state of practice in Puerto Rico’s unique tropical island topography.

18 Oct 2023

Guidelines for How to Approach Thin-Layer Placement Projects

Abstract: Historically, dredged material (DM) has been placed at the nearest available placement site. There has been an increasing trend of beneficial use projects recently, often using innovative methods. Thin-layer placement (TLP) involves one- to two-foot-thick DM placement, compared to traditional, thicker sediment placement applications, to restore coastal wetlands. The main idea of TLP is to promote the natural recolonization or reestablishment of habitat and benthic species. These guidelines present a roadmap of TLP’s evolution and offer easily digestible examples and considerations for TLP applications in wetlands and open-water environments. Offered as a tool to the practitioner, the eight chapters of these guidelines cover the history of TLP, characterization of the project area, setting goals and objectives, project design, construction considerations, monitoring and adaptive management, knowledge gaps, and future research needs. Several case studies are presented as examples of how such applications have been implemented and highlight lessons learned, particularly best-management practices. These guidelines offer consideration of TLP as a critical component in the project development phase, a tool for the sustainable management of DM, and a method that may create, maintain, enhance, or restore ecological function while supporting navigation channel infrastructure and providing flood risk management benefits.

8 Aug 2023

Evaluation of Structural and Operational Alternatives to Optimize the Distribution of Water and Sediment in the Passes of the Mississippi River

Abstract: Mississippi River shoaling and dredging processes in the vicinity of Head of Passes and in Southwest Pass were investigated. Existing rates of deposition and dredging were determined using near-daily eHydro bathymetric surveys, National Dredging Quality Management dredge operating data, and geospatial processing steps developed for this study. These surveys provide a means to characterize the highly dynamic and variable sedimentation patterns observed in the navigation channel. The HEC-6T one-dimensional numerical sedimentation model was used to evaluate possible modifications to the distribution of water and sediment in the Mississippi River near Head of Passes in an attempt to reduce shoaling in the navigation channel. The model was used to evaluate the effects of partial closures of several distributaries downstream from Venice and to evaluate the effects of channel widening and channel deepening adjacent to the Hopper Dredge Disposal Area at Head of Passes. In this study, various structural alternatives were compared to a base test that represented existing conditions. Sedimentation and dredging effects were projected 50 years into the future.

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.