Much of the NTS area is underlain by caliche hardpans, which
appear at the depth to which precipitation may reach, the result
of carrying small amounts of calcium salts in solution downward,
salt precipitation by water evaporation into the soil atmosphere,
and then loss to the open atmosphere above.
Wallace and Romney
have pointed out the possibility that Pu may also be taken into
this cycle, which is, of course, an efficient route for removing
an element from the mineral cycles of vegetation occurring there.
The possibility that Pu may reach the subsurface aquifers on a
time scale short of geological time appears very remote, or if it
did, that that water would be moved to a locality where drinking
or irrigation occurs is also remote.
In the very long terms that approach short geological time periods,
there appear to be other forces at work which may reduce Pu
availability to bioenvironmental cycles.
This is the general
geological process known as orogenic isostacy.
mountains rise, are eroded into the valleys,
By this process,
filling the valleys
at approximately the same rates as the mountains rise.
As a
result, present valley surfaces will eventually be covered by
weathered materials from the surrounding mountains and, with the
covering,
the Pu-contaminated surface will also be covered.
The
possibility is only of interest because of the very long half-
life of Pu, which is itself approaching geological time.
Finally,
there is the consideration of cost.
or may not be needed,
Fencing, which may
is certainly a very small expenditure
relative to most of the methods considered at present.
In addi-
tion, large amounts of soils will need to be moved and places
will have to be found to deposit it at further expense.
There
will be losses in transport, equipment will be contaminated, and
there will still be a potential problem in preventing redistribution even after the soils are at a new location.
to the fiscal costs,
there may be other costs.
In addition
Wallace and
Romney (1975) have pointed out some of the possibilities of longterm damage to ecosystems and those arguments will not be repeated
here.
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