Adak is known in the North Pacific as the “Birthplace of the Winds.” The weather is severe and conditions can deteriorate quickly. The challenge was to design an ABS class-approved mooring system to secure the platform through the worst-case conditions with drag embedment anchors. The project required intensive integration with engineering reviews of hardware fabricated by providers in Holland, England, China, Canada, and the Pacific Northwest.
Glosten designed the SBX permanent mooring as a conventional, catenary anchor spread with eight legs. The metocean loads drove the mooring hardware to the limits of available manufacturing, requiring 4.5-inch (114-mm) 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.
Glosten served as Boeing’s on-site representative throughout installation. Manson Construction was selected as the installation contractor. Due to the short weather window in Adak, the installation proceeded on a 24-hour 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. The project was delivered on budget and three weeks ahead of schedule.
