Demonstration Project on Dredging and Marsh Development Using a Flexible-Discharge Dustpan Dredge at Head of Passes/Southwest Pass Mississippi River

摘要

The navigation channel of the Mississippi River in the vicinity of the Head of Passes (HOP) downstream of New Orleans is an area where significant dynamic shoaling occurs. During the traditional high-water period in the spring, the shoaling in this area occurs rapidly and can represent a hazard to deep- draft vessel traffic. The shoaling must be removed rapidly to maintain adequate channel depth. Currently, dredging of the channel at HOP is conducted using hopper dredges, primarily due to their mobility. Hydraulic dredges with conventional spudding systems and floating discharge pipelines, such as cutterhead dredges, are considered a safety hazard in this area due to their inability to rapidly (and consistently) move out of the way of vessel traffic. Unfortunately, hopper dredges simply move the dredged material out of the channel and redeposit it in open-water disposal sites at the heads of Pass A loutre and South Pass. There are two disadvantages to this technique. First, the disposal sites periodically become so filled with material that the hoppers cannot bottom dump dredged material at the sites. The dredged material must be handled again at additional cost to provide sites for hopper disposal. Secondly, there is no beneficial use of the dredged material. Hopper dredges can use direct pump-out to place material beneficially in adjacent shallow open-water areas for marsh restoration, but this is considered costly and has never been done before at the HOP. This report presents the demonstration results of the dustpan dredge Beachbuilder using a flexible discharge at the Head of Passes/ Southwest Pass on the Mississippi River in June 2002 Dustpan dredges equipped with a flexible-discharge floating hose and sufficient pumping capacity potentially have the mobility required for safe passage of vessel traffic and can economically pump dredged material the distances required for placement in a beneficial use scenario such as marsh construction.