364
RADIOLOGICAL CLEANUP OF ENEWETAK ATOLL
|!
r
{
Soil Cleanup Operations
t
free of ferric interference. The effects of the causeway’s steel support
members and retaining wall were found to be minimal beyond about 10
meters. The actual measurements of field intensity were made on the
existing grid with at least three samples taken at each node to minimize
erroneousreadings. At each point, a number from oneto ten was assigned
(the higher the number, the greater the probability of ferrous metal).
The results of this survey are shown at Figure 7-29. As was expressed by
U.S. Oceanography, the magnetometer can be used to give very rough
estimates of ferric material present. Notwithstanding this uncertainty, the
use of the magnetometer survey data in combination with other survey
results greatly assisted in the overall project.
r
5
pCi/g (disregarding depth) (Figure 7-31) and the estimates of debris
AOMON CRYPT CLEANUP CONCEPTS
The objective of the Aomon Crypt Project was to removeall debris and
subsurface contaminated soil above 400 pCi/g. The Bair Committee had
determined that the Aomon Cryptwas a special case; the 160 pCi/g criteria
for subsurface contamination should not apply. As a result of the
exploratory efforts, it was concluded that a sheet pile enclosure would be
required for excavation of the heavily contaminated soii and debris around
the center (node 45NE25) of the 5-by-5-meter grid system (Figure 7-33).
With two exceptions, no other soil contamination was found above 400
ee Ge te Oeee
locations from drilling (Figure 7-32) were used in conjunction with the
magnetometer survey for further exploratory activities and designation of
the sheet pile containment area.
2
2
2
at
eel
—
Deep-drill sampling was conducted by personnel from the U.S. Army
Engineer District, Mobile, Alabama, from 26 November 1978 to I4
January !979 (Figure 7-30). The primary purpose was to jocate the areas of
soil contamination in the crypt area. To achieve this objective, soil samples
were extracted at the nodes of the preestablished 5-by-5-meter grid at
depth intervals of 2 feet. Drilling proceeded until the drill bit struck either
the base coral reef or metal. This data, when combined with the
magnetometer survey, gave a better approximation of the location of
buried debris. The samples gathered were field screened using the IMP
and analyzed through chemical analysis at the radiological laboratory on
Enewetak Island. Horizontal locations of the contaminated soil above 400
CAUSEWAY
DEEP-DRILL SAMPLING