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<br /> June 2009 Remedial Well Installations by Stantec Consulting Corporation
<br /> On June 16 and 17, 2009, Stantec Consulting Corporation (Stantec) supervised the installation of three
<br /> onsite remedial wells, OS-23 through OS-25, for oxygen injection pilot testing. OS-23 was screened in
<br /> the B Zone, OS-24 was screened in the A Zone, and OS-25 was screened in the B'Zone. No soil
<br /> samples collected during well installation were submitted for laboratory analysis. Groundwater samples
<br /> were collected from each well following well development. TPHg and TBA were detected in two of the
<br /> three wells at maximum concentrations of 410 µg/L and 5,200 µg/L, respectively, in well OS-25.
<br /> Maximum concentrations of BTEX and MTBE were detected in well OS-23 at concentrations of 130 µg/L,
<br /> 750 µg/L, 820 µg/L, 1,300 µg/L, and 11,000 µg/L, respectively.
<br /> June 2010 Remedial Well Installations by Stantec
<br /> From June 8 through 10, 2010, Stantec supervised the installation of three onsite remediation wells, OS-
<br /> 26 through OS-28, to further assess the effectiveness of injecting oxygen into the subsurface as a
<br /> remedial approach. All three wells were installed and screened in the B Zone. Soil samples were
<br /> collected every five feet during well installation, with select samples submitted for laboratory analysis.
<br /> TPHg and MTBE were detected in soil samples from each well at maximum concentrations of 1,800
<br /> mg/kg in OS-28 at 50 fbg for TPHg and 0.12 mg/kg in OS-27 at 70 fbg for MTBE. Benzene and toluene
<br /> were only detected in soil samples from OS-28 at concentrations of 5.4 mg/kg and 62 mg/kg,
<br /> respectively, at 50 fbg. Ethylbenzene and total xylenes were detected in soil samples from OS-27 and
<br /> OS-28 at maximum concentrations of 45 mg/kg and 200 mg/kg, respectively, in OS-28 at 50 fbg.
<br /> Following well development, groundwater samples were collected from each well. TPHg and BTEX were
<br /> detected in groundwater samples at maximum concentrations of 12,000 µg/L, 110 µg/L, 570 µg/L, 460
<br /> µg/L, and 1,900 µg/L, respectively, in well OS-28. MTBE and TBA were detected at maximum
<br /> concentrations of 60 µg/L in OS-27 and 8,700 µg/L in OS-26, respectively.
<br /> September 2010 Soil Vapor Probe Installations by Stantec
<br /> On September 24, 2010, Stantec supervised the installation of four temporary soil vapor probes, SG-1
<br /> through SG-4, to evaluate the potential vapor intrusion risks related to soil vapor emanating from
<br /> hydrocarbon impact to site soil and groundwater. Each soil vapor probe was installed to approximately
<br /> 5.5 fbg. Soil vapor samples were collected from each probe in 1-liter Summa canisters. Following
<br /> sampling, all four soil vapor probes were destroyed. TPHg was detected at a maximum concentration of
<br /> 1,500 micrograms per cubic meter(µg/m3) in vapor probe SG-3. BTEX were detected at maximum
<br /> concentrations of 51 µg/m3, 160 µg/m3, 12 µg/m3, and 65 µg/m3, respectively, in vapor probe SG-1.
<br /> Further information is available in Stantec's November 23, 2010, Soil Gas Survey Report.
<br /> January 2014 Soil Vapor Probe Installations by Arcadis
<br /> On January 21, 2014, Arcadis supervised the installation of two soil vapor probes, SVP-1 and SVP-2, to
<br /> verify the results of the 2010 soil vapor investigation conducted by Stantec. SVP-1 was a multilevel soil
<br /> vapor probe that was screened at 5 and 15 fbg and SVP-2 was a single vapor probe screened at 10 fbg.
<br /> Soil samples were collected for laboratory analysis during soil vapor probe installations. No petroleum
<br /> hydrocarbons were detected in any soil samples. Soil vapor samples were collected from each screened
<br /> interval using 6-liter Summa canisters. Toluene was the only petroleum hydrocarbon detected in any of
<br /> GHD I Well Installation Work Plan Addendum I Attachment B 111193145(05)1 Page 4
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