Project Trinity 1945-1946 | Page 7

was chosen for its remote location and good
weather and because it was already owned by the Government. MED

obtained permission to use the site from the Commanding General of
the Second Air Force (Army Air Forces) on 7 September 1944 (12).
Figure 1-2 shows the TRINITY site with its major installations.
* Throughout this report, surface distances are given in metric units.
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.
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. The principal
buildings of the abandoned McDonald Ranch, where the active parts of
the TRINITY device were assembled, stood 3,660 meters southeast of
ground zero. Seven guard posts, which were simply small tents or
parked trucks like the ones shown in figures 1-3 and 1-4, dotted the test
site (9).
** Universal Transverse Mercator (UTM) coordinates are used in this
report. The first three digits refer to a point on an east- west axis, and
the second three digits refer to a point on a north-south axis. The point
so designated is the southwest corner of an area 100 meters square.
1.3 THE PROJECT TRINITY ORGANIZATION
The organization that planned and conducted Project TRINITY grew
out of the X-2 Group. LASL, though administered by the University of
California, was part of the Manhattan Project, supervised by the Army
Corps of Engineers Manhattan Engineer District. The chief of MED
was Maj. Gen. Leslie Groves of the Army Corps of Engineers. Major
General Groves reported to both the Chief of Engineers and the Army
Chief of Staff. The Army Chief of Staff reported to the Secretary of

War, a Cabinet officer directly responsible to the President. Figure 1-5
outlines the organization of Project TRINITY.
The director of the Project TRINITY organization was Dr. Kenneth
Bainbridge. Dr. Bainbridge reported to Dr. J. Robert Oppenheimer, the
director of LASL. A team of nine research consultants advised Dr.
Bainbridge on scientific and technical matters (3).
The Project TRINITY organization was divided into the following
groups (3):
o The TRINITY Assembly Group, responsible for assembling and
arming the nuclear device
o The TR-1 (Services) Group, responsible for construction, utilities,
procurement, transportation, and communications
o The TR-2 Group, responsible for air-blast and earth-shock
measurements
o The TR-3 (Physics) Group, responsible for experiments concerning
measurements of ionizing radiation
o The TR-4 Group, responsible for meteorology
o The TR-5 Group, responsible for spectrographic and photographic
measurements
o The TR-6 Group, responsible for the airblast-airborne condenser
gauges
o The TR-7 (Medical) Group, responsible for the radiological safety
and general health of the Project TRINITY participants.
Each of these groups was divided into several units. Individuals were
also assigned special tasks outside their groups, such as
communications and tracking the TRINITY cloud with a searchlight
(3).

1.4 MILITARY AND CIVILIAN PARTICIPANTS IN PROJECT
TRINITY
From March 1944 until the beginning of 1946, several thousand people
participated in Project TRINITY. These included not only the LASL
scientists, but also scientists, technicians, and workmen employed at
MED installations throughout the United States. 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). Most of the military personnel were part of the
Army Corps of Engineers, although Navy and other Army personnel
were also assigned to the project (4; 12).

CHAPTER 2
THE ACTIVITIES AT PROJECT TRINITY
The TRINITY nuclear device was detonated on a 100-foot tower
(shown in figure 2-1) at UTM coordinates 630266 on the Alamogordo
Bombing Range, New Mexico, at 0530 Mountain War Time, on 16
July 1945. The detonation had a yield of 19 kilotons and left an
impression 2.9 meters deep and 335 meters wide. The cloud resulting
from the detonation rose to an altitude of 35,000 feet (5). The
TRINITY detonation is shown in figure 2-2.
At shot-time, the temperature was 21.8 degrees Celsius, and the surface