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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 µg/L, 3.6 µg/L, 9.8 µg/L, 1.7 µg/L, 8.0 µg/L, and 1.0 µg/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 /> µg/L, 2,500 µg/L, 750 µg/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 µg/L, 490 µg/L, and 2,800 µg/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 µg/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)1 Page 3
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