Carl R. Maag

“ Except during bad weather, the entire ground zero area was visible from the roadblocks. No unauthorized person was ever detected entering the ground zero area (1) .
On 10 August, the Broadway roadblocks were removed, and mounted military policemen began patrolling around ground zero at a distance of 730 meters. Each guard was assigned to a daily six-hour shift for a period of two weeks; in the third week, the guard was assigned tasks away from the ground zero area. The mounted guards and their horses wore film badges. No exposure greater than 0.1 roentgen was registered. ”

“ Because the Allied conference in Potsdam, Germany, was about to begin and the President needed the results of the test as soon as possible, the TRINITY test organization adjusted its schedules accordingly and set shot-time at 0400 hours on 16 July (3; 12; 14) .
The final preparations for the detonation started at 2200 on 15 July. To prevent unnecessary danger, all personnel not essential to the firing activities were ordered to leave the test site. During the night of 15 July, these people left for viewing positions on Compania Hill,* 32 kilometers northwest of ground zero. ”

“ The three principal centers of the Manhattan Project were the Hanford, Washington, Plutonium Production Plant; the Oak Ridge, Tennessee, U-235 Production Plant; and the Los Alamos Scientific Laboratory in northern New Mexico. At LASL, Manhattan Project scientists and technicians, directed by Dr. J. Robert Oppenheimer,* investigated the theoretical problems that had to be solved before a nuclear weapon could be developed (12) .
* This report identifies by name only those LASL and MED personnel who are well-known historical figures. ”

“ They got out of their vehicle only once, at about 460 meters from ground zero, and spent a total of about ten minutes making this trip through the area. Each man's radiation exposure measured less than 1 roentgen (1) .
Most of the soldiers of the evacuation detachment remained in their bivouac area near Guard Post 2. According to a report written by the detachment commander, a reinforced platoon was sent to the town of Bingham, about 29 kilometers northeast of the test site, while offsite radiological safety monitors surveyed the area. ”

“ Ground zero for the TRINITY detonation was at UTM coordinates 630266.** Three shelters, located approximately 9,150 meters (10,000 yards) north, west, and south of ground zero, were built for the protection of test personnel and instruments. The shelters had walls of reinforced concrete and were buried under a few feet of earth. The south shelter was the Control Point for the test (12) . The Base Camp, which was the headquarters for Project TRINITY, was located approximately 16 kilometers southwest of ground zero. ”

“ Radiation Exposures at Project TRINITY
Dosimetry information is available for about 815 individuals who either participated in Project TRINITY activities or visited the test site between 16 July 1945 and 1 January 1947. The listing does not indicate the precise military or unit affiliation of all personnel. Less than six percent of the Project TRINITY participants received exposures greater than 2 roentgens. Twenty-three of these individuals received exposures greater than 2 but less than 4 roentgens; another 22 individuals received between 4 and 15 roentgens. ”

“ According to entrance logs, film badge data, and other records, about 1,000 people either worked at or visited the TRINITY site from 16 July 1945 through 1946 (1; 3; 8; 15; 16) .
Although supervised by Major General Groves and the Army Corps of Engineers, many Manhattan Project personnel were civilians. Military personnel were assigned principally to support services, such as security and logistics, although soldiers with special skills worked with the civilians (7; 12) . ”

“ The Site Monitoring Group was responsible for equipping personnel with protective clothing and instruments to measure radiation exposure, monitoring and recording personnel exposure according to film badge readings and time spent in the test area, and providing for personnel decontamination. The Offsite Monitoring Group surveyed areas surrounding the test site for radioactive fallout. In addition to these two monitoring groups, a small group of medical technicians provided radiation detection instruments and monitoring. ”

“ Most of those who sought this authorization were scientists and military support personnel whose job required that they work near ground zero. Except for a group of two military men and three civilians who went to ground zero on 16 and 17 July and a group of two civilians who approached as close as 90 meters on 18 July, the reentry personnel came no closer than 180 meters to ground zero. Of these personnel, the individual who received the highest exposure during the three days was an Army sergeant who received 15 roentgens. ”

“ The safety criteria established for Project TRINITY were based on calculations of the anticipated dangers from blast pressure, thermal radiation, and ionizing radiation. The TR-7 Group, also known as the Medical Group, was responsible for radiological safety. A limit of 5 roentgens of exposure during a two-month period was established. ”

“ Military police at Guard Post 4 and at three roadblocks set up along Broadway controlled entry into the area. Guard Posts 3, 5, 6, and 7 were within 3,000 meters of ground zero and thus remained unmanned. At the south shelter, the Medical Group set up a "going-in" station where personnel were required to stop to put on protective clothing (coveralls, booties, caps, and cotton gloves) and pick up monitoring equipment before entering the ground zero area. ”

“ 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. ”

“ Civilian and military scientists and technicians, with assistance from other military personnel, placed gauges, detectors, and other instruments around ground zero before the detonation. Four offsite monitoring posts were established in the towns of Nogal, Roswell, Socorro, and Fort Sumner, New Mexico. An evacuation detachment consisting of 144 to 160 enlisted men and officers was established in case protective measures or evacuation of civilians living offsite became necessary. ”

“ The metric conversion factors include: 1 meter = 3.28 feet; 1 meter = 1.09 yards; and 1 kilometer = 0.62 miles. Vertical distances are given in feet; altitudes are measured from mean sea level, while heights are measured from surface level, unless otherwise noted. ”