The first drydock ARCO was ARD 29. Built by the Pacific Bridge Company in Alameda, California, it was requisitioned by the Navy in 1944 and placed in service at the Navy Repair Base, San Diego, California. Modifications were made to ARD 29 in preparation for its relocation to forward remote refit sites in the Pacific. On the 23rd of June 1946, the drydock was commissioned USS ARD 29. Shortly after commissioning the drydock was towed to Guam, arriving on the 2nd of September 19046. After completing a one year assignment in Guam and Okinawa, the drydock was relocated to Pearl Harbor, Hawaii where it remained for the next twelve years. In 1959 the drydock returned to Guam. It was during this assignment that the Navy adopted the practice of naming Auxiliary Repair drydocks after towns having nuclear power generators or nuclear research facilities. On 28 March 1967 the USS ARD 29 received the name "ARCO". This name was in recognition of the town of Arco, Idaho. The USS ARD 29 (ARCO) ended is active role in the United States Navy on the 1st of November 1971 when it was transferred to the Imperial Iranian Navy. In 1977 the drydock was removed from the register of United States Naval Vessels. It was designated drydock No. 400 by the Iranian Navy and was still active as late as 1985.
ARCO (ARDM 5), the second drydock to bear the name ARCO, was built by the Todd Pacific Shipyard Corporation, Seattle, Washington. The second of a new class of medium drydocks, construction began in June 1983. ARCO was placed in service on 23 June 1986. ARCO has a lifting capacity of 1800 long tons, is 492 feet long, 96 feet wide and has a wing wall height of 61 feet. The drydock is equipped with two wing wall cranes capable of lifting up to 25 tons each. The ballasting pumps are capable of pumping a combined capacity of ten thousand gallons per minute. ARCO is used primarily for dry-docking and servicing 637 and 688 class submarines.
ARCO (ARDM 5) is a Submarine Squadron ELEVEN asset under the operational control of Commander, Submarine Force, U.S. Pacific Fleet. The crew consists of approximately 130 personnel.