and the specified removal criteria.
Mr. McCraw read extracts from the four
removal criteria contained in the operations plan (OPLAN 600-77) (Encl 6).
Miss Barnes stated that it would be impossible to reach even the 50 percent
confidence level of not having missed significant subsurface contamination
without doing much more profile sampling.
For example, to find a particular
region of contamination two feet wide, under worst case with the seam parallel
to the grid lines, would require sampling every four feet.
To provide such
characterization would require commitment of substantial resources.
If the characterization is done on a simple yes-no criteria the sampling
need not be so precise.
Using the highest contamination level recorded on the
island, 3200 pCi/g, Dr. Crites demonstrated a calculation showing that a pocket
of contamination which would average greater than 400 pCi/g over a 21 meter
(68.8 ft) field of view would be approximately seven meters in diameter,
Thus
sampling on a grid of less than seven meters should locate such a minimum
pocket size subsurface contamination of interest.
There was discussion of the one half distance technique for determining
the presence or absence (yes~no) of subsurface contamination.
Available data
indicates only a few sample locations showing subsurface contamination at
greater than 400 pCi/g levels.
a 200 foot grid,
Sample locations are spaced on approximately
Moving one half the distance between greater than and less
than sampie points iteratively should provide boundary definition of contamination areas of interest.
This investigation would be limited to those areas
where available data indicates high subsurface contamination levels, thus
reducing the effort involved.
of the iterative half distance.
The "7 meter" criteria would set the lower bound