5900 WEST MARGINAL WAY SW
Feb. 27, 2026:
Glacier is proposing maintenance dredging at its facility located on the LDW at 5900 West Marginal Way
Southwest in Seattle, Washington (Sheet 1 of Attachment 1). Due to increased sedimentation experienced in
this reach of the LDW (approximately 4 inches per year on average), a portion of the existing berth at the
Glacier dock no longer achieves authorized depths of -35 feet mean lower low water (MLLW). Therefore,
maintenance dredging is required to provide adequate depths for berthing and safe access to the terminal.
The Project includes removing up to 12,000 cubic yards (CY) of sediment within the approximately 2.2-acre
berth area (Sheets 2 and 3 of Attachment 1). Maintenance dredging is proposed to a depth of -34 feet MLLW,
with an additional 0.5 foot of overdredge allowance, to a total of -34.5 feet MLLW. Dredge controls, such as
GPS-supported dredge positioning systems, will be in place during maintenance dredging to ensure a
maximum depth of -34.5 feet to avoid disturbance to the existing clean sand cover that was placed as part of
a 2005 maintenance dredging effort. Maintenance dredging activities will occur entirely within the previously
maintained berth area.
Prior to 2005 the berth was maintained to a permitted depth of -35 feet, with an additional 1-foot overdredge
allowance, to -36 feet MLLW. In 2005, the 1-foot clean sand cover was placed in the bottom of the berth to
protect the water column from contaminants observed in the underlying sediments. The current Project does
not include placement of a clean sand cover, since the existing clean sand cover, plus a minimum 0.5 foot of
existing accumulated sediment, will remain in place. The area will continue to be subject to ongoing sediment
accumulation. This approach was approved by the U.S. Army Corps of Engineers, U.S. Environmental
Protection Agency, and Washington State Department of Ecology as part of 2017 and 2024 maintenance
dredging efforts. Maintenance dredging activities will occur entirely within the existing berth area.
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