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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 4101.1g/L and 5,200 p.g/L, respectively, in well OS-25.
<br />Maximum concentrations of BTEX and MTBE were detected in well OS-23 at concentrations of 130 p.g/L,
<br />750 p.g/L, 8201.ig/L, 1,300 1.1g/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 [ig/L, 110 p.g/L, 570 µg/L, 460
<br />1.1.g/L, and 1,900 p.g/L, respectively, in well 05-28. MTBE and TBA were detected at maximum
<br />concentrations of 60 p.g/L in OS-27 and 8,700 4/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 (pg/m3) in vapor probe SG-3. BTEX were detected at maximum
<br />concentrations of 51 .rg/m3, 160 ig/m3, 121.ig/m3, and 65 ig/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 />GH D 1Well Installation Work Plan Addendum !Attachment B111193145 (05)1 Page 4
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