EPPERSON arrived in the Pacific Proving Grounds on January 24, 1954 to begin preparations for the operation. As a member of the Surface Security Unit, EPPERSON’s general function was to provide security for Bikini and Eniwetok Atolls. Specifically the Task Unit's duties included search and rescue missions to investigate submarine contacts, to warn and divert unauthorized shipping from the danger area, and to escort ships transporting shot devices from Eniwetok to Bikini.

At 6:45 a.m. on March 1, 1954 the first CASTLE event, Test BRAVO, was detonated at Bikini. EPPERSON was on AntiSubmarine Warfare Patrol 10 miles southwest of Eniwetok, approximately 210 miles west of ground zero.

On March 27, the second CASTLE event, Test ROMEO, was detonated at 6:30 a.m. in Bikini Lagoon. EPPERSON was 37 miles southeast of ground zero. Approximately eight hours after the detonation, EPPERSON anchored in Bikini Lagoon. The ship remained anchored for one hour and 37 minutes before departing the lagoon. At 6:00 p.m., while on security patrol 50 miles northwest of Bikini, EPPERSON reported receiving fallout. One hour later, the ship left the area to avoid unnecessary personnel exposure. In addition, the ship’s washdown system was activated from 7:33 p.m. to 7:50 p.m. to reduce the contamination level.

The next day, EPPERSON returned to Bikini Lagoon, anchoring at 8:08 p.m. At about 7:30 p.m. on March 23, most of the task group ships anchored in Bikini Lagoon began receiving slight fallout. Employment of washdown systems (EPPERSON’S was reactivated on March 29 for 27 minutes), vigorous decontamination and natural radioactivity decay steadily reduced contamination.