Port of Portland's Changes in Maintenance Dredging: Barge Unloading and the New Dredged Material Rehandling Facility

This paper describes the process that the Port of Portland went through to manage its maintenance dredge material after its in-water disposal options were eliminated. That process included the search for new disposal options, an overview of the considered dredge material management concepts and the selected alternative. The paper also describes details of the design considerations and features for the selected alternative such as the Dredged Material Rehandling Facility (DMRF). The selected alternative consisted of a conventional clamshell dredging operation into barges that were later offloaded into the DMRF by a submersible agitator pump hung from a floating crane. The used agitator pump is capable of pumping high percentage solids and the fluidizing water jets that are attached to it are an effective way to help liquidize the dredged material. The paper specifically focuses on the barge unloading process that was selected, the equipment used for that process (including the 10-inch submersible agitator pump) and the engineering design of the operation. Experiences gained from the project are addressed with some interesting lessons learned about pump capabilities and performance, the dewatering phase of the dredged material, how environmental rules were applied, and the workability of the chosen concept. Some insights about the financial figures of the project available from the post-project review and evaluation are also included.