Port of Seattle, Army Corps agree on tentative dredging plan

The port said the improvements are needed in order for it to handle the current and future generations of ultra-large containerships.

   The Port of Seattle and the Army Corps of Engineers have agreed on a tentative plan to deepen the waterways at the mouth of the Duwamish River where it empties into Puget Sound’s Elliot Bay.
   The port said the improvements are needed so it can handle current and future generations of ultra-large containerships.
   The plan recommends dredging to 57 feet Mean Lower Low Water (MLLW) for both the East and West Duwamish Waterways on either side of Harbor Island.
The project would benefit vessels calling container facilities such as Terminals 5, 18, 30 and 46 in Seattle. Berths at the terminals currently range in depth from 40-50 feet.
   On Tuesday, The Army Corps released the Seattle Harbor Navigation Improvement Project Draft Feasibility Report and Environmental Assessment and said comments on the plan will be accepted through Aug. 31, 2016.
   The East and West Duwamish Waterways have been identified by the Army Corps and port as the areas of critical importance for navigation improvements.
   “The purpose of the proposed Federal action is to achieve transportation cost savings (increased economic efficiencies) at the East and West Waterways of Seattle Harbor,” the Army Corps said in the report. “Navigational challenges have been identified in both the East and West Waterways of Seattle Harbor and authorized depths do not meet the draft requirements of today’s fleet of larger container ships. Tide restrictions, light loading, or other operational inefficiencies created by inadequate channel depth result in economic inefficiencies that translate into costs for the national economy.”
   The Army Corps looked at six alternative plans – four for the East Waterway and two for the West Waterway.
   In order to deepen both the East and West Waterways to 57 MLLW in both the East and West Waterways, approximately 777,000 cubic yards from the West Waterway would have to be dredged, along with 341,000 cubic yards from the East Waterway.
   The estimated cost is $78.1 million.
   “The Port of Seattle, part of The Northwest Seaport Alliance, is a strategic gateway for goods entering the U.S. and vital for Northwest exports,” said John Creighton, who is president of the Port of Seattle Commission and co-chairman of the Northwest Seaport Alliance.
   “Large ships with deep drafts are being deployed globally and on the West Coast. Authorization of a depth of 57 feet will preserve our gateway’s ability to provide sufficient depth for the future fleet of ships,” said Connie Bacon, who is the Port of Tacoma Commission president and Creighton’s co-chair at the Northwest Seaport Alliance.