Third Quarter 2019 Groundwater Monitoring (Partial):
3.3.1 Volatile Organic Compounds
Tetrachloroethene (PCE) and trichloroethene (TCE) are the primary VOCs that were detected in the groundwater samples collected from the monitoring wells. PCE was detected in 31 of the 32 wells sampled at concentrations ranging from an estimated 0.34J micrograms per liter (μg/L) in well MW-100 to 4,100 μg/L in well MW-9. The reported PCE concentrations were above the California maximum contaminant level (MCL) for drinking water standard of 5 μg/L in 27 of the 32 monitoring wells. TCE was reported in all of the wells at concentrations ranging from an estimated 0.74J μg/L in well MW-11 to 1,400 μg/L in wells MW-2 and MW-104. TCE was reported at concentrations above its California MCL of 5 μg/L in 30 of the 32 monitoring wells.
Some of the breakdown or “daughter products” from the degradation of PCE and TCE and other chlorinated VOCs can include cis-1,2-dichloroethene (DCE), trans-1,2-DCE and vinyl chloride. In addition to these compounds, other chlorinated VOCs reported in groundwater samples collected at the site include 1,1-DCE, 1,1-dichloroethane (DCA), 1,2-DCA and 1,1,2-trichloroethane (TCA). The distribution of these VOCs and other non-chlorinated VOCs in the wells that exceed their respective California MCLs are as follows:
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Cla-Val 1701 Placentia Avenue, Costa Mesa, California Project No. 14-0124
• cis-1,2-DCE: Reported in all 32 wells at concentrations ranging from an estimated 0.92J μg/L to 4,200 μg/L. Twenty-five wells had cis-1,2-DCE reported above its MCL of 6 μg/L.
• trans-1,2,-DCE: Reported in 25 of 32 wells at concentrations ranging from an estimated 0.22J μg/L to 27 μg/L. Four wells had trans-1,2-DCE reported at or above its MCL of 10 μg/L.
• 1,1-DCA: Reported in 22 of 32 wells at concentrations ranging from an estimated 0.99J μg/L to 5.8 μg/L. One well had concentrations of 1,1-DCA reported above its MCL of 5 μg/L.
• 1,1-DCE: Reported in 30 of 32 wells at concentrations ranging from an estimated 0.31J μg/L to 37 μg/L. Eleven wells had concentrations of 1,1-DCE reported above its MCL of 6 μg/L.
• 1,2-DCA: Reported in 8 of 32 wells at concentrations ranging from an estimated 0.20J μg/L to 2.3 μg/L. Three wells had concentrations of 1,2-DCA reported above its MCL of 0.5 μg/L.
• Vinyl Chloride: Reported in 21 of 32 wells at concentrations ranging from an estimated 0.21J μg/L to 3.6 μg/L. Nine wells had concentrations of vinyl chloride reported at or above its MCL of 0.5 μg/L.
• Benzene: Reported in 21 of 32 wells at concentrations ranging from an estimated 0.20J μg/L to 1.4 μg/L. Five wells had concentrations of benzene reported above its MCL of 1.0 μg/L.
Other VOCs reported during the first quarter 2019 sampling event below their respective MCLs or those which do not have an MCL included the following compounds:
• 1,4-Dioxane: Reported in 9 of the 9 wells sampled at concentrations ranging from an estimated 1.3J μg/L to 81 μg/L.
• 1,1,2-TCA: Reported in 12 of 32 wells at concentrations ranging from an estimated 0.22J μg/L to 3.0 μg/L.
• Chloroform: Reported in 23 of 32 wells at concentrations ranging from an estimated 0.20J μg/L to 13 μg/L.
• Chloroethane: Reported in 1 of 32 wells at an estimated concentration of 0.41J μg/L.
• Chlorobenzene: Reported in 13 of 32 wells at concentrations ranging from an estimated 0.21J μg/L to 1.3 μg/L.
• Methyl Tertiary Butyl Ether (MTBE): Reported in 4 of 32 wells at concentrations ranging from an estimated 0.32J μg/L to 2.9 μg/L.
The analytical results for VOCs reported in the groundwater monitoring well samples collected to date are shown on Table 4. It should be noted that sampling of wells for 1,4-dioxane had been suspended since the fourth quarter 2017 sampling event, but was started again during the third quarter 2018 for nine wells (RS, 2018). Previous results for 1,4-dioxane are also included in Table 4. Select VOCs found in groundwater are shown on Figure 4. The PCE and TCE plumes are shown on Figures 5 and 6,
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Click The Link Below for information on the vapor risk from migrating VOC's known as
The off gas ⬇️⬇️
