Dredging in Sediments Containing Munitions and Explosives of Concern (MEC)

Abstract

This document provides guidance to personnel (e.g., planners, cost estimators, specification writers, engineers, managers, and dredging contractors) involved in dredging projects with sediment containing Munitions and Explosives of Concern (MEC). The guidance is primarily in the form of compiled information gained from experiences on past dredging projects involving MEC and was compiled from a variety of sources. This report describes the different types of dredges and dredging projects that can encounter MEC, describes how these dredges' operational methodologies can be impacted by MEC, and summarizes past project methodology modifications that have been used to deal with MEC. Technical aspects of past MEC/dredging projects are presented with regard to engineering controls to mitigate detonation hazards, underwater MEC detection and discrimination technologies, contracting, public awareness, safety requirements, and MEC separation techniques and (where available) subsequent impacts on production rates and costs.

Screening dredged material to meet placement requirements

“…Summary descriptions of the different types of dredges and their general operational methodologies were described in Chapter 3. These different pieces of equipment and respective operational methodologies influence the design and installation location (in the dredging process) of the screening system (or systems) (Welp et al 2008). The type of dredge used (i.e., hydraulic or mechanical) will have a profound impact on the physical characteristics of the DM (and how it can be efficiently screened) throughout the excavation/removal/transport/placement process.…”

“…The size, number, and composition of objects that require separation, in conjunction with the way it is removed from the process stream and properly disposed of, must be considered. Technical aspects of the separation and safe disposal of MEC is discussed in detail in Welp et al (2008) with regard to engineering controls to mitigate detonation hazards, MEC separation techniques, contracting, public awareness, safety requirements, and (where available) subsequent impacts on production rates and costs.…”

“…Screening can be divided into two general categories -static (stationary) or vibrating. Past MEC projects described by Welp et al (2008) have predominantly used static screening. For hydraulic dredges, these screens have been installed with varying degrees of success:…”

“…• extraction of Munitions and Explosives of Concern (MEC) to address safety concerns • removal of oversized material for beneficial use of DM (e.g., gravel and debris from sand to meet beach nourishment placement standards) • pre-processing DM to remove oversized material and debris to prepare it for subsequent treatment (e.g., hydrocycloning, filter belt presses) • removal of debris to avoid creating hazards to commercial fishing and navigation, altering habitat quality, and jeopardizing public acceptance of the continued use of open-water disposal or placement sites 1.2 Objective Welp et al (2008) provide detailed guidance for personnel (e.g., planners, cost estimators, specification writers, engineers, managers, and dredging contractors) involved in dredging projects with sediment containing MEC.…”

“…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.…”