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RADIOLOGICAL CLEANUP OF ENEWETAK ATOLL

with an average of 97 pCi/g before plowing. Soil profile readings showed a

rapid drop in contamination levels, a factor of 10 in the first 10
centimeters, and no elevated subsurface readings.
Four 25-by-25-meter areas were reserved as control areas and four were
selected for plowing. Most debris and vegetation was removed, and soil

sampling holes in these areas were filled and smoothed. The plow was
pulled by a USAE-operated D8 bulldozer, plowing to 3-foot depths with no

difficulty. The plow’s hydraulic system for raising and lowering the blade
was inoperative, therefore a front loader was used to drive the point into

the ground and lift it out. Consequently, plowing was accomplished by
making large turns at the ends of the furrows with the blade left in the

ground. Brush, dead limbs, and old signal cables tended to foul the plow
and had to be removed by bulldozer. Two of the plowed areas contained
good, dark earth down to approximately 30 centimeters while cover on the
other two was mostly coral and very shallow.

Plowed areas had to be backbladed with a bulldozer to provide a plane
surface for IMP measurement. The IMP surveys showed considerable
reduction in surface contamination on the plowed areas and nosignificant

changein the control areas.’
Frequent rain stabilized the soil, facilitating subsurface soil sampling.

Trenches cut with a backhoe retained their vertical structure. The soil in
the trench walls appeared to be well mixed, although occasional darker
patches and layers of organic origin appeared in the lighter coral regions.
The plowing experiment confirmed that, under the conditions foundat
Enewetak, surface contamination could be reduced substantially by
plowing. A multivariate statistical analysis confirmed the expectation that
the distribution of contamination would be altered considerably along the

entire profile.
Contamination was generally mixed throughout the plowedprofile, but

some was deposited at depths with little mixing. In mixed areas, the
contamination washighly diluted regardless of the original concentration.
Hot spots in concentrations of 25 to 50 percent of that of the original
surface contamination levels were foundatall of the depths sampled, with

most being observed at 30 centimeters or deeper. The Plow-X area
subsequently was reduced to less than 40 pCi/g by standard soil removal

procedures.
The plowing experiment was eminently successful, and it showed that—
without question—plowing could be used effectively to reduce surface

transuranic contamination and thus reduce thelikelihood of transuranic

resuspensionin air, with its potential inhalation hazard. However, VADM

Monroefirmly regarded plowing as a ‘‘measureof last resort.’’ He saw two
significant drawbacks that would result from plowing:

First, as pointed out by the Bair Committee, plowing merely distributed
the transuranics to lower levels in the soil. It in no way reduced the

bE

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