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November 2004 Monitoring Well Installation by SECOR
<br />From November 9 through 12, 2004, SECOR supervised the installation of one onsite groundwater
<br />monitoring well, MW-15, to monitor the vertical extent of hydrocarbon impact to groundwater. The well
<br />was installed to approximately 120 fbg. No soil samples were collected during well installation.
<br />Groundwater samples were collected following well development. TPHg, BTEX, and EDC were detected
<br />at concentrations of 89 p.g/L, 3.6 p.g/L, 9.8 µg/L, 1.7 µg/L, 8.0 µg/L, and 1.0 p.g/L, respectively. Further
<br />information is available in SECOR's July 28, 2005, Results of Vertical Assessment and Updated Site
<br />Conceptual Model.
<br />April 2005 Monitoring Well Installations by SECOR
<br />From April 11 through 15, 2005, SECOR supervised the installation of two onsite groundwater monitoring
<br />wells, MW-16 and MW-17, to monitor the vertical extent of hydrocarbon impact to groundwater. The wells
<br />were installed to approximately 120 fbg. No soil samples were collected from well MW-16; however, soil
<br />samples were collected from MW-17 at 10-foot intervals from 80 to 120 fbg. Groundwater samples were
<br />collected from each well following development. No petroleum hydrocarbons were detected in soil
<br />samples except for total xylenes at a concentration of 0.017 mg/kg in MW-17 at 120 fbg. TPHg and
<br />BTEX were detected in groundwater from both wells at maximum concentrations of 30,000 µg/L, 1,100
<br />p.g/L, 2,500 1g/L, 750 IA g/L, and 4,100 µg/L, respectively, in well MW-17. Further information is available
<br />in SECOR's July 28, 2005, Results of Vertical Assessment and Updated Site Conceptual Model.
<br />January 2006 Monitoring Well Redevelopment and Well Survey by SECOR
<br />On January 25, 2006, SECOR redeveloped groundwater monitoring well MW-17 to verify that previous
<br />groundwater samples were representative of conditions within the depth interval accessed by the well.
<br />The well was redeveloped by surging the well over the length of the screen interval and purging
<br />groundwater for approximately eight hours using air lift methods. Following redevelopment, well MW-17
<br />was sampled. TPHg and EDC were the only petroleum hydrocarbons detected at concentrations of 220
<br />µg/L and 2.1 µg/L, respectively.
<br />SECOR conducted a search for wells located within a one-mile radius of the site using Environmental
<br />Data Resources, Inc.'s (EDR) radius search. Ten wells were identified within one-mile of the site. Four of
<br />these wells were within one-half mile of the site. All wells were identified as up- and crossgradient from
<br />the site. Further information is available in SECOR's April 19, 2006, MW-17 Redevelopment Report.
<br />January 2008 Monitoring Well Installations by SECOR
<br />In January 2008, SECOR supervised the installation of five groundwater monitoring wells, MW-18 through
<br />MW-22, to delineate the newly named B' Zone located approximately between 55 and 70 fbg. Wells MW-
<br />18 through MW-21 were installed to approximately 65 to 70 fbg, and well MW-22 was installed to
<br />approximately 43 fbg. No soil samples were collected during well installation. Groundwater samples
<br />were collected following well development. TPHg was detected in groundwater samples from each well
<br />at a maximum concentration of 20,000 µg/L in well MW-18. BTEX were detected in groundwater samples
<br />at maximum concentrations of 130 µg/L, 520 p.g/L, 490 µg/L, and 2,800 p.g/L, respectively, in well MW-21.
<br />MTBE was detected in all five wells at a maximum concentration of 9,500 µg/L in MW-19. Tert-butyl
<br />alcohol (TBA) was detected in all five wells at a maximum concentration of 9,600 p.g/L in well MW-21.
<br />Further information is available in SECOR's May 7, 2008, Well Installation Report.
<br />GHD I Well Installation Work Plan Addendum I Attachment B 111193145 (05) I Page 3
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