The 53rd Naval Construction Battalion (NCB) was established on December 22, 1942 and served throughout the remainder of WWII, primarily on the Pacific Islands of Guadalcanal, Bougainville, and Guam. As post-war activities were nearing completion, the battalion was scheduled for inactivation on March 1, 1946. The inactivation was cancelled when the unit was selected to participate in Operation Crossroads, a series of nuclear weapon tests conducted by the United States at Bikini Atoll in the Marshall Islands, in mid-1946. Operation Crossroads was the first test of a nuclear weapon since the Trinity nuclear test in July 1945, and the first detonation of a nuclear device since the atomic bombing of Nagasaki on August 9, 1945. Its purpose was to investigate the effect of nuclear weapons on naval warships, equipment, and material.
The 53rd NCB arrived at Bikini Atoll on March 13, and then transferred to the USS St. Croix, which was anchored in the atoll lagoon. This ship served as the battalion headquarters throughout the Bikini operation. Drawing on their wartime experience in fast construction, nearly 1,000 Seabees with the 53rd NCB transformed Bikini Atoll into a huge laboratory where instruments and structures were set up to record the blast.
The composite battalion of stevedores, pontoon builders, and construction men began the main construction projects which included the erection of several 90-foot towers and protected steel huts for housing the instruments used for recording the blast data, the day after they arrived on site.
Offloading of supplies and equipment
Heavy equipment, to include bulldozers, trucks, and cranes were brought by LST, along with more men and supplies arriving from Pearl Harbor and Port Hueneme, CA.
Seabees with the 53rd NCB constructing a tower to hold automatic camera as part of Operation Crossroads. The towers were built on an island near Bikini Atoll to document the Atomic Bomb explosion.
Seabees built 15 steel towers for photographic observation, several wooden frame towers, and advanced base magazines measuring 20 feet by 20 feet.
The Bikini Atoll is comprised of 30 islands, and Seabees completed projects on 9 of these. Among these projects were demolition operations to remove coralheads to enable LSTs and small craft to land on the beaches, along with the construction of recreational facilities for 35,000 men, to include baseball fields, basketball courts, tennis courts, and an archery range. Construction efforts were made extremely difficult by the constant churning of the black, sandy soil on the beach, which became choking dust clouds as vehicles were transported back and forth. DDT, then unknown to be hazardous to health, was sprayed repeatedly from low-flying planes to combat the hordes of flies that were constantly plaguing the Seabees as they worked.
Aerial view showing one of the many construction sites operated by the 53rd NCB at Bikini Atoll
The Baker Day explosion of the fifth atomic bomb, Bikini as recorded by an automatically operated camera on a nearby island. Characteristic atomic clouds forms, altered by steam from sub-surface detonation
Operation Crossroads consisted of two detonations, each with a yield of 21 kilotons of TNT (96 terajoules): ABLE was detonated at an altitude of 520 feet (160 m) on July 1, 1946; BAKER was detonated 90 feet (27 m) underwater on July 25, 1946. A third burst, CHARLIE, a deep underwater detonation planned for 1947 was canceled due to the inability to decontaminate the target ships following the Baker test.
With the completion of Operation Crossroads, the battalion was inactivated on August 3, 1946 after 38 months of continuous overseas duty. Some battalion members were transferred back to the United States for separation from the Navy, while others remained onsite for cleanup and restoration duties on Bikini. These members were assigned to the newly activated Naval Construction Battalion Detachment 1156.