(2) indicates the effect of plowing Engehi only while modification (3) reflects
the additional effect of plowing all the northern islands.
Deeper plowing
or turning over the soil rather than mixing it would of course result in
even greater exposure rate reductions.
For example mixing to a depth of two
feet would reduce gamma exposure levels by an additional factor of two, while
covering ‘the sources with approximately a foot of uncontaminated soil would
essentially reduce the eventual integral gamma-ray doses from 137 cs and ©0¢9
to negligible values, ive.. doses everywhere similar to those calculated for
case IV.
Removing the first 6 inches of top soil which now usually contains
over two thirds of the activity, rather than plowing, would result also in
am mo
about a factor of three reduction in‘exposure rates.
Based on the result given in Table IV, however, extensive modifications
may not be necessary.
If we compare the unmodified integrated exposures with
values calculated for typical U. S. sea level locations which are also given
in Table IV, we see that even for Cases I, and Lp the 70 year integral
dose is only slightly greater than the comparable "typical" U. S. value.