Enclosure (1) TO COMDTINST 16478.12
"background" level, was established at each location based upon the value of
the "perimeter" of 20 meters. This level established an on-site comparison
value for each mercury. The other values presented in Figure 3-9 reflect the
state and nationally established levels of concern for these metals in
sediment. These levels are established by a complex statistical method
described in the notes following at the end of this chapter. The important
point regarding these criteria is that they provide comparison values at which
various environmental or health effects might be expected.
In most cases, sample values were at or below the ER-M levels, however, there
were some elevated levels detected during post removal sampiling. In some
cases the level of mercury in comparable samples before and after removal
increased by over 800%, but they were not typical. Since the number of cases
of increases are low (in fact in some cases the percent changes are negative),
it appears that either the sample randomly discovered a "concentration spot"
or battery removals contributed to a transient recontamination of the field.
3-16
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