St. Croix Mooring Design

This report presents the design of a mooring to service surface ships and submarines operating off the west coast of the island of St. Croix, West Indies. This emergency mooring is required because the nearby Frederiksted Pier was damaged during tropical storm Klause on 1 November 1984. The mooring will accommodate large submarines ( Lafayette SSBN 616 or smaller) and a wide variety of surface ships ( Spruance DD963 was selected as typical). These vessels have the following characteristics: DD 963 Spruance, length-564 ft., max. draft-30 ft., mooring swing-750 ft., SSBN 616 Lafayette, length-421 ft., max. draft-32 ft., mooring swing-560 ft. Both static and dynamic ship/mooring forces and interactions are considered and a Class A mooring with 100 kips working holding capacity was selected. This corresponds to a maximum 2.0 knots current with a simultaneous 50 knot, 30-second duration wind. The surface ships control the design forces. The buoy is to be located 500 yards north of the pier in a water depth of 60 feet. Because of the great uncertainty in bottom conditions the mooring will be installed and tested and the rating of the mooring will be re-evaluated in January 1985. Design adjustments may be made based on those results and/or installation experiences. Drag anchors as well as Propellment Embedment Anchors will be mobilized to cover installation contingencies.