How does Seaway maintain the stability of the excavation after the vertical barrier wall is removed?
During the course of traditional contaminated sediment cleanup operations, sediments are removed in layers to avoid deep cuts that could result in wall instability and sediment collapse into the bottom trenches produced during the excavation. This method of excavation results in the exposure of sub-bottom layers of contaminated sediments to the water column. The contaminated sediments in these sub-layers, which in many instances may be more contaminated than upper sediment layers, are free to migrate from the dredge site, until further passes (digs) over the area can be made. The Seaway Mobile Containment Vessel permits the excavation to proceed directly to the design depth by using the vertical barrier wall (sheet piles) of the control zone to provide the structural stability to maintain the excavation. All exposed sub-layers are contained within the control zone until the cleanup is completed. Where excavation depths are such that wall stability is in question, prior to the removal o
