Island, where there is increased runoff and recharge from large runway and
tarmac surface areas devoid of vegetation, does the lens water remain fresh.
Thus, the amount of potable ground water is not only dependent on the geolog:
of the island and the amount of annual rainfall, but also the density of
vegetation on the island.
With the current stand of vegetation on Bikini Island, a very heavy
rainfall, or lighter rainfall
occurring with short time intervals between
rainfall episodes, is required to produce a flow through to the lens.
The
total annual rainfall] and the rate at which it is delivered is very important
to the level of recharge of the lens in a given year.
For example, the
rainfall of 77 inches in 1986 was the highest in several
years and the
groundwater salinity decreased as a result; however, the salinities in the
various wells were still, for the most part,
high enough to render the water
unpotable.
REMEDIAL MEASURES
Based on the current concentrations of !3/Cs in vegetation and soil on
Bikini Island and our current diet model, it will take about 80 to 90 y for
radiological decay of '37Cs to reduce the !37Cs concentrations to a level that
the estimated radiological dose to residents from all exposure pathways would
be below current Federal guidelines.
As a result, we have been evaluating several
potential
methods for
reducing the amount of !37cs in the soil column and/or blocking the transfer
of '37cs from soil to plants. In general terms, the methods can be classified
as follows:
1}.
Excavation.
2.
Chemical competition.
3.
Matrix immobilization.
4.
Repeated cropping of vegetation.
Some of these options have been evaluated and rejected.
For example,
repeated cropping of vegetation that contains !'3/cCs, and its subsequent
disposal, to reduce the !3/Cs content of the soil is not a reasonable
solution.
The
limited
fresh
water
supply at
the Atoll
eliminates
any
consideration of irrigation on an island-wide basis, thus limiting the choice
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