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Repair Dry Dock Cofferdam Sheet Piles


Project Name: Repair Dry Dock Cofferdam Sheet Piles
Location: Naval Base Kitsap-Bangor, Washington
Contract Number: N44255-11-C-9005
This project consisted of the removal of Delta Pier's dry dock's old failing sheet pile barrier and replacing it with a new protective concrete facing on the exterior surface of the cofferdam sheet pile from the top of the exposed sheets, approximately +20 MLLW, down to -2 MLLW. Many design and construction challenges were faced in this project. Some of them include: restricted access due to security measures, operational constraints, limited lay down space, a high tidal range, difficult under-deck working conditions, and tight environmental constraints. Despite these challenges, the project finished ahead of schedule. Water blasting was used both above and below the water surface to remove the old failing sheet pile coating. Shear studs were then welded onto the sheets to attach the concrete facing as well as threaded studs for the form ties. Reinforcing bar was pre-curved and individually tied to the welded studs. Forms were then placed onto the ties and concrete placed inside the forms. The majority of the work was done on a specially designed, multilevel scaffolding system which allowed adequate spacing from the sheets for the required concrete coverage. All concrete was batched off site, delivered, and placed within specified time constraints. A test wall segment of the dry dock was indicated in the contract design documents to prove Triton's means and methods as well as evaluate the concrete facing. The facing was designed to be highly durable, have low permeability, and have low shrinkage. Since the concrete is not for structural support, the mix design had to be tested and accepted before construction could begin. Once approved, and after fully testing and inspecting the test wall segment's concrete, it was found to be acceptable and full production was allowed to proceed. This part of the project required close oversight by the quality control and management team from Triton, the concrete supplier, the third party inspection agency, NAVFAC, and the government engineers.