Operation CROSSROADS was a two-detonation atmospheric nuclear test series occurring at Bikini Atoll in July 1946.
SALT LAKE CITY arrived at Bikini Atoll on May 29, 1946 to prepare for the operation. The ship was designated as on of the target vessels used at CROSSROADS. All target vessels were placed under special training standards involving personnel evacuation, re-boarding techniques and damage control training.
Prior to the first CROSSROADS event, Test ABLE on July 1st, the entire crew of the SALT LAKE CITY was evacuated to the USS ROCKBRIDGE (APA-228). At CROSSROADS one of the primary duties of the several personnel transports such as ROCKBRIDGE was to house the crews of the target ships during and following the two detonations. The crews of the target ships that were subsequently sunk or rendered uninhabitable by Tests ABLE and BAKER continued living aboard the transport ships well after the detonations.
On the morning of July 1st, ROCKBRIDGE departed the lagoon and at 9:00 a.m. observed Test ABLE (air detonation) at a distance in excess of 21 miles from ground zero. Eight hours later it anchored in the lagoon. Test ABLE caused only minor radiological contamination to the lagoon and virtually none to the non-target ships such as ROCKBRIDGE.
SALT LAKE CITY was anchored approximately 895 yards from ground zero. As a result of the test, the ship was immobilized and sustained moderate damage to the decks, sides and bottom. Because SALT LAKE CITY was uninhabitable, due principally to boiler damage with consequent lack of power for operating generators, pumps, auxiliary machinery, etc., the crew remained temporarily quartered aboard ROCKBRIDGE.
On July 2, the commanding officer, a radiological safety monitor and 30 men boarded SALT LAKE CITY to conduct an inspection. After three hours, the boarding party returned to ROCKBRIDGE. From July 3rd through July 6th, crewmembers boarded SALT LAKE CITY for approximately eight hours a day to conduct clean-up operations. With the exception of a security detail that remained aboard the ship overnight on July 5th and 6th, the boarding parties returned to ROCKBRIDGE at night.
Assisted by tugs, SALT LAKE CITY changed berths twice on July 6th. The next day, all SALT LAKE CITY personnel disembarked ROCKBRIDGE and returned to quarters aboard SALT LAKE CITY.
On July 13th, SALT LAKE CITY was once again towed to a new berth. In July 16th, 86 men were assigned to temporary quarters aboard ROCKBRIDGE. Over the next two days the rest of the crew boarded ROCKBRIDGE to participate in the rehearsal for the second CROSSROADS event, Test BAKER. With the exception of 95 men, SALT LAKE CITY personnel returned to the ship on July 19th.
On July 23rd, 55 men were transferred to ROCKBRIDGE in preparation for Test BAKER. The next morning the remaining crewmembers were transferred to ROCKBRIDGE, and at 8:35 a.m. on July 25th, observed Test BAKER (shallow underwater detonation) at a distance of 16 miles from surface zero. In order to let the radioactivity in the lagoon abate to a safe level (less than 0.1 rem gamma per 24 hours), ROCKBRIDGE did not return to the lagoon until July 30th. SALT LAKE CITY was anchored approximately 1120 yards from the detonation point. The ship suffered little structural damage but was radiologically contaminated from the base surge caused by the underwater explosion. This precluded anyone from going aboard the ship for the next week.
On August 1st, a work party of less than 50 men boarded SALT LAKE CITY to perform general duties which included pumping out flooded spaces and washing down the main deck areas with high pressure hoses. That afternoon the boarding parties returned to ROCKBRIDGE.
From August 2nd-9th, two boarding teams, normally consisting of 50 men, continued to board SALT LAKE CITY each day to conduct radiological surveys, decontamination and clean-up and repair operations. Each of these teams was aboard two hours.
On August 4th, the fresh water system was returned to operation and the water was declared radiologically safe to drink. The ventilation systems were cleared by the Radiological Safety Section on August 9th. All members of the boarding parties were carefully monitored (body checks for contamination were made daily) to guard against excessive radiation exposure, and remained quartered aboard ROCKBRIDGE.
On August 10th, all SALT LAKE CITY boarding parties were suspended. Two days later, members of the Radiological Safety Section checked all clothing which had been worn by men working aboard SALT LAKE CITY. Clothing and shoes registering above the tolerance level were collected and later disposed of by dumping at sea in weighted bundles. Navy data indicates that several members of the crew were sent to USS HAVEN (AH-12) for additional radiological monitoring. The results of those tests are presently unknown.
On August 12th and 13th, two teams of 80 men each boarded the ship for two hour periods to inspect the ship for damage.
On August 17th, 19 unidentified crewmembers boarded SALT LAKE CITY to heave in the port anchor. They were aboard three and one half hours before they evacuated the ship. Twenty-five members of the crew boarded the ship August 19th for four hours to prepare for an inspection. They all returned to ROCKBRIDGE after being given a radiological clearance in a special decontamination barracks ship (APL). The next day twenty-six men spent three hours aboard SALT LAKE CITY during an inspection. Before returning to ROCKBRIDGE they also were given radiological clearances in the APL.
SALT LAKE CITY was taken under tow by USS CHICKASAW (ATF-83) for Kwajalein Atoll on August 23rd. Six members of SALT LAKE CITY's crew were temporarily assigned to CHICKASAW to assist in the towing operation. The remaining SALT LAKE CITY crew arrived at Kwajalein from Bikini aboard ROCKBRIDGE on August 24th. When SALT LAKE CITY arrived at Kwajalein on August 25th, the special detail dropped anchor and returned to ROCKBRIDGE, having completed its assignment. Prior to SALT LAKE CITY's decommissioning on August 28th, the crew was officially transferred to various ships for further assignment.
ROCKBRIDGE was one of the operating ships in CROSSROADS whose involvement caused it to be temporarily listed as radiologically suspect. A degree of contamination did occur to virtually all of the non-target ships which remained in Bikini Lagoon for over ten days after Test BAKER. This was largely caused by low level radioactive contamination of the lagoon waters following Test BAKER and was confirmed to the exterior hull at or below the waterline and the internal salt water piping systems. However, in order to prevent contamination of the drinking water, CROSSROADS ships were instructed to scrape off marine growth near the waterline, not to steam evaporators in excess of 80%, and not to dismantle the evaporators without a radiation monitor being present.
A careful search of dosimetry data for CROSSROADS revealed that out of a total of 272 crewmembers and an undetermined number of passengers aboard ROCKBRIDGE, 18 individuals were issued film badges. During CROSSROADS film badges were issued to a percentage of the crew originally assigned to some of the ships. Film badges were generally issued to those personnel who re-boarded target ships or worked in other contaminated areas. The film badges of three individuals were either not returned of were rendered unreadable due to adverse environmental factors. Thirteen individuals received recorded radiation exposure readings of zero rem gamma; two badged ROCKBRIDGE personnel received exposure readings of 0.05 rem gamma each. (Nine of these badges were issued for the July 1st time period; seven badges were issued on August 12th, and two on August 13th.)
Out of a total of 338 crewmembers and an undetermined number of other persons embarked on SALT LAKE CITY during CROSSROADS, 212 individuals were issued film badges. Twenty-seven individuals' film badges were either not returned or were rendered unreadable due to adverse environmental conditions. The recorded mean for the remaining 185 badged individuals was 0.74 rem gamma with a range of exposure from zero to 0.87 rem gamma. SALT LAKE CITY badging was essentially limited to portions of August 1946.
Compared to other tests, exposures for CROSSROADS are relatively low. Approximately 99% of all recorded radiation exposures at CROSSROADS ranged from zero to 0.5 rem gamma. The highest recorded cumulative radiation exposure for any individual at CROSSROADS was 3.72 rem gamma. This exposure is within present national occupational radiation exposure standards which permit 5.0 rem gamma per year.