Built by the Zenith Dredge Company of Duluth, Minnesota, the ship was laid down on 16 September 1943, and launched on 11 November 1943.
Based at Kodiak, she carried out numerous search and rescue operations, fought fires, delivered medical supplies, and enforced fishing laws.
Bittersweet was then stationed at Woods Hole, Massachusetts and used for ATON and icebreaking. In addition she took part in oil spill cleanup operations and also participated in the International Ice Patrol.
Bittersweet was decommissioned on 18 August 1997, and given to Estonia. Renamed Valvas, the ship served in the Estonian Border Guard until it was decommissioned in July 2014 and given to the Estonian Maritime Museum. It is to become a museum ship.
The Iris-class buoy tenders were constructed after the Mesquite-class buoy tenders. Bittersweet cost $926,769 to construct and had an overall length of 180feet. It had a beam of 37feet and a draft of up to 12feet at the time of construction, although this was increased to 14inchesft7inchesin (ftin) in 1966. It initially had a displacement of 935lt; this was increased to 1026lt in 1966. It was powered by one electric motor. This was connected up to two Westinghouse generators which were driven by two CooperBessemer GND-8 four-cycle diesel engines. It had a single screw.[1]
The Iris-class buoy tenders had maximum sustained speeds of 13kn, although this diminished to around 11.9kn in 1966. For economic and effective operation, it had to initially operate at 8.3kn, although this increased to 8.5kn in 1966. The ship had a complement of six officers and seventy-four crew members in 1945; this decreased to two warrants, four officers, and forty-seven men in 1966. It was fitted with a SL1 radar system and QBE-3A sonar system in 1945. Its armament consisted of one 3"/50 caliber gun, two 20mm/80 guns, two Mousetraps, two depth charge tracks, and four Y-guns in 1945; these were removed in 1966.[1]