Glosten provided engineering services and owner’s representation to The Boeing Company for the installation of a permanent eight-point MODU style mooring for the semi-submersible SBX-1 at Adak, Alaska. The SBX-1 is designed for heavy weather operability as part of the U.S. Defense Department Ballistic Missile Defense System.
Designing a System to Safely Secure SBX
Adak is known in the North Pacific as the “Birthplace of Winds”. The weather is severe and conditions deteriorate quickly. The challenge was to design an ABS class approved mooring system to secure the platform with drag embedment anchors through the worst-case conditions. The project required intensive quality vetting with engineering reviews of hardware fabricated by providers in Holland, England, China, Canada, and the Pacific Northwest.
Rigorous Analysis Program Proves the Design
Glosten designed the SBX permanent mooring as a conventional, centenary anchor leg system with eight legs. The metocean loads drove the mooring hardware to the limits of available manufacturing, requiring 4.5 inch RQ4 chain and 75 ton record-setting Stevpris anchors. A rigorous numerical analysis program was developed to model the system, prove the design, and gain ABS class certification. Glosten supported Boeing in developing the proposal for the installation contract, selecting the contractor, and managing the geophysical and anchoring condition surveys.
Successfully Installed Ahead of Schedule
Manson Construction, Seattle, Washington, was selected as the installation contractor. Due to the short weather window in Adak, the installation proceeded on a 24 hr basis. Many tons of derelict World War II anti-submarine nets were removed from the seabed before the mooring legs were installed. The project was completed when all eight 75-ton anchors were embedded and cross tensioned to a proof load of 900 tons. Glosten served as Boeing’s on-site representative throughout installation. The project was delivered on budget and three weeks ahead of schedule.
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