The military policemen refused to return to Guard Post 2, insisting that they had received orders over their two-way radio from the Base Commander to evacuate their post and head for San Antonio, New Mexico, a town 28 kilometers northwest of the Guard Post. The Base Commander had noted that portions of the cloud were heading northwestward and, fearing that fallout from the cloud would contaminate Guard Post 2, had ordered the military police to evacuate. The chief monitor, however, had found no significant radiation levels anywhere along the northern part of Broadway nor around Guard Post 2. The Base Commander, after being contacted by the chief monitor, drove to the foxholes and ordered the guards to return to their post. This was the only unplanned incident during the onsite monitoring (1). After Guard Post 2 was reoccupied, the chief monitor returned to the roadblock at the intersection of Broadway and the North Shelter Road. The north shelter monitor informed the chief monitor of the sudden evacuation of the north shelter, whereupon the chief monitor surveyed the north shelter area and found intensities of only 0.01 and 0.02 roentgens per hour (R/h). The chief monitor then contacted the south shelter and informed Dr. Bainbridge that the north shelter region was safe for those who needed to return, that Broadway was safe from the Base Camp to Guard Post 2, and that Guard Post 2 was now manned so that personnel leaving for LASL could be checked out (1). The chief monitor then returned to the south shelter and assembled the monitors from the three roadblocks and Guard Post 4 to prepare for entrance into the ground zero area. The time was about 0815 hours. The military police at the roadblocks were given radiation meters to survey the adjoining area. Broadway from the south shelter to Guard Post 2 was remonitored occasionally to reassure the military police that there was no radiation problem. Monitors also surveyed the Base Camp for 24 hours after the detonation. No radiation above background levels was detected there (1). The following brief description of the radiological environment in the TRINITY test area is based primarily on the results of the remote gamma recorders situated in the test area and on results of the road surveys conducted after the detonation (1). Within about 1,400 meters of ground zero (except to the north), radiation intensities between 0.2 and 1.3 R/h were detected during the first few minutes after the detonation. These readings decreased to less than 0.1 R/h within a few hours. At greater distances to the east, south, and west, radiation levels above background were not detected (1).