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samples from MW-6 with maximum concentrations of 55.3 mg/kg and 157 mg/kg, respectively, at 60 fbg.
<br />Ethylbenzene and MTBE were detected in soil samples from wells MW-5 and MW-6 at maximum
<br />concentrations of 71 mg/kg and 33.8 mg/kg, respectively, at 60 fbg. Total xylenes were detected in soil
<br />samples from all three wells at a maximum concentration of 204 mg/kg in MW-6 at 60 fbg. In
<br />groundwater samples,maximum concentrations of TPHg, benzene, and total xylenes were detected in
<br />well MW-6 at concentrations of 2,300 p.g/L, 22 µg/L, and 79 µg/L, respectively. Maximum concentrations
<br />of toluene and ethylbenzene were detected in well MW-5 at concentrations of 15 µg/L and 16 µg/L,
<br />respectively. MTBE was detected at a maximum concentration of 16 µg/L in well MW-7. Further
<br />information is available in IT Corporation's August 16, 2001, Vertical Assessment Report.
<br />August and September 2001 Monitoring Well Installations by IT Corporation
<br />On August 30 and 31, and September 5, 2001, IT Corporation installed three groundwater monitoring
<br />wells, MW-8 through MW-10, to further delineate the vertical extent of hydrocarbon impact to groundwater
<br />beneath the site. All three wells were installed at approximately 80 fbg with the screened interval from
<br />approximately 69 to 79 fbg. Soil samples were collected every five feet during well installation and
<br />groundwater samples were collected following well development. TPHg and BTEX were detected in soil
<br />samples from each well with maximum concentrations of 4,400 mg/kg, 77 mg/kg, 50 mg/kg, 34 mg/kg,
<br />and 210 mg/kg, respectively, in MW-9 at 60 fbg. No MTBE was detected in any of the soil samples.
<br />Elevated hydrocarbon concentrations were reported in groundwater samples from each of the three wells.
<br />Maximum concentrations of TPHg, toluene, ethylbenzene, and total xylenes were detected in well MW-9
<br />at concentrations of 22,000 p.g/L, 260 µg/L, 1,100 p.g/L, and 3,600 p.g/L, respectively. The maximum
<br />concentration of benzene was detected in well MW-8 at 600 µg/L. No MTBE was detected in any of the
<br />groundwater samples. Further information is available in SECOR International Incorporated's (SECOR)
<br />May 29, 2002, Site Assessment Report.
<br />June and July 2003 Monitoring Well Installations by SECOR
<br />Between June 6 and July 11, 2003, SECOR installed four offsite groundwater monitoring wells, MW-11
<br />through MW-14, to delineate the lateral and vertical extent of hydrocarbons in groundwater. Select soil
<br />samples collected during well installation were submitted for laboratory analysis and groundwater
<br />samples were collected following well development. No TPHg, BTEX, or MTBE were detected in any soil
<br />samples. TPHg, benzene, toluene, and MTBE were only detected in groundwater samples from well
<br />MW-12 at concentrations of 65 µg/L, 0.57 µg/L, 0.63 p.g/L, and 2.2 µg/L, respectively. Further information
<br />is available in SECOR's September 30, 2003, Results of Offsite Assessment and Site Conceptual Model.
<br />May 2004 Soil Borings by SECOR
<br />From May 3 through May 7, 2004, SECOR advanced two onsite soil borings, SB-1D and SB-2D, to
<br />approximately 120 fbg to delineate the vertical extent of hydrocarbons in groundwater. Soil samples were
<br />collected continuously from 80 to 120 fbg during borehole advancement and groundwater samples were
<br />collected from each boring. No petroleum hydrocarbons were detected in any of the soil samples
<br />collected. The only petroleum hydrocarbon detected in groundwater samples was 1,2-Dichloroethane
<br />(EDC) at a concentration of 0.72 µg/L in SB-2D(VV) at 110 fbg. Further information is available in
<br />SECOR's August 13, 2004, Results of Vertical Assessment and Updated Site Conceptual Model.
<br />GHD I Well Installation Work Plan Addendum 1 Attachment B111193145 (05)1 Page 2
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