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Table 2, below, is a summary of the analytical results for a site in Virginia Beach, VA Figure 6 <br /> is a plot of benzene and DO concentrations and Figure 7 is a plot of benzene and ferrous iron, for <br /> the five monitoring wells at this site. The monitoring well network did not allow for the same <br /> concentration versus distance analysis as shown above for the Fairfax terminal. However, the <br />' inverse correlation observed between benzene and DO concentrations m Figure 6 suggests the <br /> role of aerobic biodegradation. In Figure 7, the higher ferrous iron concentrations in wells with <br /> the highest benzene concentrations suggest anaerobic biodegradation may be contributing to the <br /> configuration of the contaminant plume <br /> Table 2 <br /> Virginia Beach, VA <br /> Groundwater Analytical Data <br /> Sampling Date: 11/8/94 <br />' dissolved ferrous total <br /> monitor benzene oxygen iron redox titrate sulfate alkalinity <br /> well (ppb) (22M) m (m H m tri) to <br /> MW-1 <RL 112 01 282 177 116 59 25 <br /> MW-2 <RL 5 16 24 246 548 11 20 21 <br /> MW-3 <RL 238 2 235 573 61 58 43 <br /> MW4 310 <10 X10 -118 61 0 081 39 140 <br /> MW-5 610 0 3 7 5 -215 557 <RL 54 78 <br /> Note. RL is reporting IMUL <br /> Any of the following trends observed across a dissolved contaminant plume (with increasing <br /> contaminant concentrations) would suggest the potential occurrence of intrinsic bioremediation• <br /> A relative decrease in- A relative increase in- <br /> dissolved oxygen ferrous iron <br />' oxidation-reduction potential alkalinity <br /> nitrate <br /> sulfate <br />' The demonstration of intrinsic bioremediation rel P requires multiple lines of evidence, including <br /> analytical data which suggest bioremediation is actually realized in the field. The evaluation of <br />' indicator parameters across a dissolved contaminant plume can be used in the demonstration of <br /> intrinsic bioremediation. <br /> 1 ' <br /> 16 <br />