Environmental Engineering Reference
In-Depth Information
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MWG107B
Upgradient
MWG101B
Denit. PRB
MWG112B
between
MWG104B
ZVI PRB
MWG110B
Downgradient
Monitoring well
FIGURE 7.12
Nitrate concentrations measured along cross-section C-C′ for B series monitoring wells.
7.10 Chlorinated Solvent Concentrations
Concentrations of chlorinated solvents at monitoring locations at the ends of
the PRBs (MWG13, MWG114, MWG115, MWG116, MWG117, and MWG118)
and in the Leederville formation (D series sampling locations) indicate that
the TCE plume is being captured by the remediation system. The concentra-
tion of TCE downgradient of the PRBs has been consistently below the eco-
logical screening criteria.
Concentrations for TCE, DCE, and vinyl chloride (VC) measured during
the quarterly monitoring program for the B series wells along the plume cen-
terline (Section C-C′ shown in Figure 7.10) are presented in Figures 7.13, 7.14,
and 7.15, respectively. Concentrations of TCE, DCE, and VC were converted
into a molar mass and the A, B, and C series results summed to obtain a
molar mass value for each location for the first four groundwater rounds and
are presented in Figure 7.16. Owing to a decrease in the number of sampling
location in subsequent quarterly monitoring rounds, only the total molar
mass for the upgradient (MWG107) and downgradient (MWG110) sample
locations are available and are presented in Figure 7.16.
Concentrations of chlorinated solvent within both the denitrification and
ZVI PRBs are usually below detection limits but occasionally they are detected
at levels only marginally above laboratory detection limits. Chlorinated com-
pounds have been detected downgradient of the system. It is currently uncer-
tain whether this is a rebound phenomenon or if samples collected from within
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