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concentrations of 930 milligrams per kilogram (mg/kg) at 2.8 mg/kg, respectively. 1,2-DCA was
<br /> detected in the soil samples collected from the borehole of MW5 at 50 and 89 feet bgs, MW6 at
<br /> ' 89.5 feet bgs, MW8 at 50.5 feet bgs, and MW9 at 50.5 feet bgs.
<br /> MTBE, DIPE, ETBE, TAME, EDB, and TBA were not detected in soil samples collected from
<br /> ' the boreholes MW5 through MW12. Analytical results of soil samples are summarized in Table
<br /> 3. Laboratory data sheets and chain-of-custody documentation are presented in Appendix D.
<br /> 4.2 Groundwater Analytical Results
<br /> Groundwater samples were not collected from MW7 and MW11 due to an obstruction in MW7
<br /> and grout infiltration in MWI1. BTEX constituents were detected in all of the groundwater
<br /> samples, with the exception of the groundwater sample collected from MW4. The highest
<br /> concentrations of benzene, 8,200 micrograms per liter (ug/L) and 6,700 ug/L, were detected in
<br /> the groundwater samples collected from MW8 and MW1, respectively. TPHg was detected in
<br /> the groundwater samples collected from MW1, MW2, MW3, MW5, MW6, MW8, and MW12.
<br /> ' The highest concentrations of TPHg, 120,000 ug/L and 54,000 ug/L, were detected in the
<br /> groundwater samples collected from MW1 and MW8, respectively. MTBE was detected in the
<br /> groundwater samples collected from MW2, MW3, MW9, MW10, and MW12 at concentrations
<br /> ranging from 1.5 ug/L to 55 ug/L. The highest concentration of MTBE was detected in the
<br /> groundwater sample collected from MW2. 1,2-DCA was detected in the groundwater samples
<br /> collected from MW through MW6, MW8, MW9, MW10, and MW12 at concentrations ranging
<br /> ' from 2.7 ug/L to 860 ug/L. The highest concentration of 1,2-DCA was detected in the
<br /> groundwater sample collected from MW8. TBA was detected in the groundwater samples
<br /> collected from MW2 and MW3 at concentrations of 53 ug/L and 29 ug/L, respectively.
<br /> 1 Analytical results of groundwater samples are summarized in Table 4. Laboratory data sheets
<br /> and chain-of-custody documentation are presented in Appendix D.
<br /> 5.0 CONCLUSIONS
<br /> ' The laboratory analytical results of soil samples collected from the vadose zone at approximately
<br /> 50 feet bgs indicate petroleum hydrocarbon impact in the vadose zone is generally confined to
<br /> the vicinity of MW7. Low concentrations of 1,2-DCA were detected in vadose zone soil samples
<br /> ' collected from the boreholes of MW5, MW8, and MW9. Low concentrations of petroleum
<br /> hydrocarbons were detected in soil samples collected from below the water table in the boreholes
<br /> of MW5, MW6, MW7, and MW8.
<br /> Petroleum hydrocarbons were detected in groundwater samples collected from all of the wells
<br /> sampled (MW1 through MW6, MW8, MW9, MW10, and MW12). MW4, MW9, and MW10
<br /> were least impacted and MWI and MW8 were most impacted. Benzene isoconcentration maps
<br /> for the shallow groundwater bearing zone and intermediate groundwater bearing zone are shown
<br /> r" on Figures 9 and 10, respectively. 1,2-DCA isoconcentration maps for the shallow groundwater
<br /> s:lEnviromenta11283491reports\sum.doc 5 ATC Associates Inc.
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