Site updated:

20th August 2019

USS San Francisco collides with undersea mountain.

On 8 January 2005, San Francisco collided with an undersea mountain 400 miles south of Guam while operating at about 35 knots and more than 500 feet deep. The vessel was almost lost and there was a desperate struggle for positive buoyancy after the forward ballast tanks were ruptured.

Twenty-three crewmen were injured, and one died. Injuries included broken bones, lacerations, and back injuries. San Francisco's forward ballast tanks and sonar dome were severely damaged, but her inner hull was not breached and there was no damage to her nuclear reactor. She surfaced and, accompanied by support vessels arrived in Guam on 10 January. Later, an examination of the submarine in drydock showed unmistakably that the submarine had indeed struck an undersea mountain which had only vague references on the charts available to San Francisco.

The seamount that the San Francisco struck did not appear on the chart in use at the time of the accident, but other charts available for use indicated an area of 'discolored water', an indication of the presence of a seamount. The Navy determined that information regarding the mount should have been transferred to the charts in use, particularly given the relatively uncharted nature of the ocean area that was being transited; and that the failure to do so represented a breach of proper procedures.

As San Francisco recently had her nuclear fuel replaced and thus was expected to remain in-service until 2017, the Navy determined that repair of the vessel was in its best interests. San Francisco transited to Puget Sound Naval Shipyard for extensive repairs. Given the extensive damage to San Francisco's bow section, including some warping of her pressure hull, part of her forward compartment was replaced with that of USS Honolulu after she was decommissioned in 2006.

USS San Francisco was launched in 1979, displaces 6145 tons, and has a length of 110m. Propulsion is from one S6G reactor. Complement is 12 officers and 115 crew. Click on any thumbnail below to get an expanded view.