DOE received several different estimates of the total volume of soil removed from Kickapoo. The
results for each of these estimates using mixed linear and exponential assumptions are:
Volume Distribution
Areas with
Estimate of
Total Volume Estimate
Subsurface
Total Volume
Contamination
Areas without
Total
Contamination
Removed
Subsurface
cu. yd.
cu. yd.
Activity
Ci
7 July 78, J3
22 July 78,
B Co 84th Engr
4000
1175
2825
0.45
4400
1290
3110
0.50
sample sheets
4500
1320
3180
0.51
22 July 78, FRST-truck
In order to check how much effect the models chosen have on the estimates of total activity
removed, the estimates were repeated assuming only linear gradients. That is, the average for areas
without subsurface contamination was computed as
0.5(131 + 31.8) = 81.4 pCi/g TRU.
In areas with subsurface contamination, the assumption was that the gradient was linear with a
positive slope of 20 em and linear with a negative slope below 20 em. The average concentration
would then be
0.4 [0.5(203 + 194)]+ 0.6
[0.5(194
+ 85.4)]
= 0.4 (198.5) + 0.6 (139.7) = 163.2 pCi/g TRU.
The computed activity removed for the various volume estimates under the all-linear assumptionis:
Estimated
Total Activity
Total Volume
Removed
4000 cu. yds.
4400 cu. yds.
4500 cu. yds.
0.50 Ci
0.55 Ci
0.56 Ci
The differences between the models are far less than the difference between the two methods (IMP
versus truck samples). The IMP methodis preferable for a number of reasons:
1,
2.
3.
4.
5.
The truck samples are biased high.
Truck volumes are difficult to estimate accurately, and are not likely to be consistent.
IMP readings average over a large area, thus taking a larger sample of the population.
IMP readings are unbiased and have much lower variance than soil samples.
Total activity computations are fairly insensitive to errors in fitting a function to the soil
gradient.
Therefore, the values derived by the mixed linear and exponential models are to be considered the
most reliable, and the IMP sampling data is preferable for future computations of total activity
removed.
(Editor's Note:
Following thorough reappraisal of various measurement parameters (ef. Tech Note
23) the final estimates of TRU activity in soil removed from Island Sally are:
Yuma 0.28 Ci; Hustead, 0.16 Ci; Aomon Crypt, 0.93 Ci; Island Total, 2.22 Ci).
B~-10-4
Kickapoo, 0.85 Ci;
shen
Date & Source of