the islands of Gene and Flora, and only a sand bar now remains to
The types of nuclear events, shot frequencies, geographical locations,
distinguish the island of Helen.
Only 39 of the original 42 islands of
yields, generated particles, conditions after the tests, and other
the Atoll remain and make up a total land area of approximately 6.9 km?
factors determined the resulting distributions of transuranics and
that is situated on the reef whose area is 84 km,
in
influenced the physical and chemical forms of the elements deposited
the lagoon is 47.4 m;
km’.
the maximum depth is 60 m.
The average depth of
The lagoon area is 933
The main components in the
lagogn sediments included foraminifera, coral, Halimeda remains, shells
of mollusks, and fine material.
A brief historical review of testing at
Enewetak, abstracted from several unclassified documents
The sedimentary components in Enewetak Lagoon were studied
extensively during the late 1940s (Hm54),
the benthic environment.
(Ne73, Ci64,
Hi62), explains a few conditions responsible for the trarnsuranic
distributions and inventories at the Atoll].
The test series at Enewetak began jin 1948
Material finer than 0.5 mm in diameter
(Operation Sandstone)
was too fine to identify and was classified as fine debris.
towers on
when 37-, 49-, and 18-kt devices were detonated from ?00-{t
Distributions and average abundance of the sedimentary components were
14 May.
the islands of Janet, Sally, and Yvonne between 14 April and
described
1951,
(Em 54),
Fine debris made up 57% of the lagoon sediments and
testing was resumed
(Operation Creenhouse) and foul
In
tower shots
was abundant throughout the lagoon to within a few hundred feet from the
was again
were conducted during a 4?-da interval. The island of Janet
shore.
the location of two ground zeros.
A detailed description of the forms, living habits, populations,
In 1952,
the first thermonuclear
The
reef.
device (Mike) destroyed the island of Flora on the northwest
and specific relationships of the aquatic biological components at the
Mike event was a 10.4-Mt surface detonation occurring on Jl October,
Atoll is beyond the scope of this report.
Water surging from the point of the explosion sent a wave over adjacent
A significant number of
The
articles that were published between 1955 and 1974 and resulted from
zeros.
islands including Janet, the site of three previous ground
research conducted at the Enewetak Marine Biological Laboratory were
and
original crater where Flora had once been had an irregular outline
compiled recently in a three-volume report (En76).
refilled
was more than 1 mi in diameter, which, before it was partially
The individual
reports dealing with specific ecological studies at the Atoll, are too
ft deep.
by the returning rush of coral sediment, was almost 200
numerous to list.
crater is presently 90 ft deep,
The reader is referred to the compilation (En76)
descriptions of the biology
for
and ecology of the Atoll,
The most severe radiological impact on the aquatic environment of
Enewetak occurred during the nuclear test years between 1948 and 1958.
The 1952 series of
The
tests concluded with
the King event, a high-yield air drop over Yvonne Island.
In 1954 2
ever Mike
single device, Nectar, wis detonated on a Large Jocrted
Crater.
Not only did this test greatly disturb the radionuclides
DOD ARCETTRE