Seattle’s most extensive current civil works project,the Alaskan Way Viaduct replacement tunnel,is being constructed using the world’s largest tunnel boring machine ‘Bertha’. Due to the proximity of the construction site to the waterfront,the dirt and rock spoils from this effort are transported via conveyor belt to Pier 46. From there it is loaded onto barges for further transport.
Progress was recently halted due to an incident involving a spoils barge and a badly damaged pier.
In the early morning hours,the barge being utilized began to list and then capsize. Tunneling operations were halted due to the partially capsized barge at the adjacent pier and an impending rising tide.
The tunnel project personnel called Global’s 24 hour number to request immediate assistance. Global dispatched a Salvage Master who was on scene within 30 minutes of the call.
Following the removal of the unstable barge from underneath the pier,Global commenced a full salvage assessment. This included analysis of the barge’s stability and an underwater survey. The spoils had shifted on the barge causing it to list heavily to one side. Global developed a lightering plan and engaged a crane barge with a clamshell bucket to transfer the loose spoils to another barge.
As a precaution,Global positioned high capacity pumping equipment on location. Draft measurements monitored throughout the lightering indicated the presence of an unbalanced load in the barge. During the operations significant damage to the barge was observed. This information was incorporated into the lightering plan to ensure the safety of the operation. Following the lightering procedure,Global removed the damaged bin rails and prepared the barge for transit through the Ballard Locks.
The pier sustained significant damage to the fender piling from the capsizing barge. Global’s team quickly developed and proposed a repair plan. Following approval,Global removed the damaged piling and drove new steel replacements.
Additionally,it was determined a new fender system was required before loading operations could resume. Global’s team designed and installed an approved fender system allowing the project to continue tunneling operations.
Global provided salvage,environmental,and marine construction services to expedite and safely resolve this unexpected incident.