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15
16
oaNORTH >
FIGURE B-9-8. Plow X~1 Soil Sampling Locations
Locations denoted "( )" were deep (about 120 cm) sample holes made prior to site
selection to characterize the soil down to coral bedrock or water. The "x" locations were
profile sampled to 50 em before plowing to better define the radioactivity profile over the
plow experiment area in the region in which mixing was expected to occur due to
plowing. Those positions designated "o" were sampled to 50 em depth after plowing for
evaluation of the plowing effects. Tables B-9-1 and -2 summarize the results of IMP
screening the pre-plow profile samples.
Only the 241Am (pCi/g) results are given in each case. Samples were taken with the
standard 5 em thick sidewall sampling tool. Sample depth designates the centerline of the
sample point unless a spread is denoted (i.e., 5 to 10) in which case these are the sample
boundaries. Sample locations are keyed to the grid coordinates shown in Figure B-9-8.
For example: 1-13 is the center "( )" of the lower lefthand corner block of Figure B-9-8
and 2.25-16.25 is the "x" in the upper righthand corner block of Figure B-9-8.
A plot of the average 241Am activity versus sample depth, for the four blocks plowed,
is given in Figure B-9-9,
Plowing Experience
1.
Site Preparation
One of the first tasks involved was to fill in those holes dug for soil profile sampling by the
backhoe. Once these were smoothed, the area was carefully staked and the control plots were
roped off. Miscellaneous debris were dragged from the site and brush was generally cleared
out. Though vegetation cover in this area was relatively light, a front-end loader was used to
remove most of it. A concrete block about 0.5 m cube was found buried just below the surface
in the corner of block 2-14. This was removed with a front-end loader prior to starting
plowing. "Control" areas were cleared to a lesser extent than planned plow areas.
2.
Problems Encountered/Challenges Met
The inability of the hydraulic ram to raise and lower the plow required that a front-end loader
Stand by to put the point in the ground and lift it out. This inconvenience resulted in plowing
around the plot, through each section, without taking the plow out of the ground. Much brush
B-9-16