How are contaminated sediments removed from the containment zone?
Contaminated sediments are removed with a mechanical (clamshell bucket), which provides the most favorable (low) liquids-to-solids ratio for dredging. In Level 2 or 3 containment, operations, sediment excavation is followed by settling and subsequent vacuuming of the dispersed sediments (fluff) from the bottom of the containment zone. This is accomplished using a cutterless vacuum dredge developed by Seaway. This two-phased dredging approach (bucket dredging followed by a cutterless vacuum polishing step) provides for a more effective cleanup, which is more apt to meet target cleanup standards than traditional sediment dredging approaches. In Level 3 operations, all spillage or dispersion of particulates during excavation is contained within the control zone. Bucket washing is unnecessary. Buckets may be drained of free or excess water directly into the control zone to reduce the quantity of water carried with the sediment.
