Impervious (AM-245), an Admirable-classminesweeper, was under construction by Tampa Shipbuilding Co., Inc., Tampa, Fla., but was canceled 6 June 1944.
(AM-449: dp. 630; l. 172'; b. 36'; dr. 10'; s. 16 k.; cpL 72; a. 1 40mm.; cl. Agile)
Impervious (AM-449) was launched by Martinolich Shipbuilding Co., San Diego, Calif., 29 August 1952 ; sponsored by Miss Mary Lin Moore; and commissioned 15 July 1954, Lt. Comdr. A. T. Ford in command.
Following shakedown and mine warfare training off the California coast, Impervious was reclassified MSO-449 on 7 February 1955. She sailed 1 July with her division for duty in the Far East with the 7th Fleet, arriving Sasebo via Pearl Harbor 5 August. During this deployment, she operated with ships of the Republic of Korea Navy and visited Taiwan before returning to her home port, Long Beach, 15 February 1956. During the next two years she operated out of Long Beach.
Impervious sailed for her second 7th Fleet deployment 3 January 1958, and during the next 6 months trained in Japanese waters. She also helped train Nationalist Chinese crews during April and May, preparing them to help to preserve the freedom and independence of Taiwan. The minesweeper returned to Long Beach 15 July 1958, and during September took part in a giant amphibious exercise off Camp Pendelton, Calif.
In April 1959 Impervious interrupted her regular training schedule to take part in a joint mine warfare exercise with Canadian ships, and spent the rest of the year on training exercises in California waters. In early 1960 the ship prepared for another deployment to the Far Bast, sailing 3 May for Japan. During August she participated in maneuvers with Korean and Nationalist Chinese ships, and in October Impervious operated with units of the Philippine Navy in similar operations off Corregidor. She sailed via Guam and Pearl Harbor to Long Beach, arriving 16 November.
The ship spent 1961 and early 1962 on important readiness operations, visiting several West Coast ports, and sailed again for 7th Fleet duty 7 April 1962. After training in the Philippines the minesweeper spent part of July on patrol with Vietnamese Naval units off Danang, and the Navy supported the South Vietnamese people in their fight for freedom. She visited Hong Kong and Yokosuka before arriving Pearl Harbor 8 September 1962. During October and November, Impervious took part in atomic tests at Johnson Island, and arrived Long Beach 21 November.
In March 1963 the ship took part in another large amphibious operation, "Steelgate", then worked out of Long Beach before again joining Canadian ships for mine warfare exercises off British Columbia in November. She got underway for the western Pacific again 8 May 1964, and after stopping at various islands moved to the coast of South Vietnam in September for special operations supporting the American Advisory unit. After mine exercises off the Philippines she returned Long Beach 7 December 1964. The following 12 months were spent in tactics and exercises along the coast of southern California, overhaul at Los Angeles, and readiness operations to prepare her for another Far Eastern deployment assisting Allied forces to defend freedom in Southeast Asia.