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<br /> ASSOCIATES I N C .
<br /> petroleum hydrocarbons as diesel (TPHd) utilizing Environmental Protection Agency (EPA)
<br /> Method 8015B; benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA Method
<br /> 8021B; and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE) di-isopropyl
<br /> ether (DIPE), tertiary amyl ether (TAME), tertiary butyl ether (TBA), 1,2-dichloroethane (1,2-
<br /> DCA), and 1,2-dibromoethane (EDB) utilizing EPA Method 8260B. Groundwater well purge
<br /> and sample logs are contained in Attachment 1.
<br /> 2.1 Groundwater Flow Direction
<br /> Water levels were measured in MWl through MW5, MW6a, MW6b, MW6c, MW7a, MW7b,
<br /> MW7c, MW8, MW9a, MW9b, MW9c, MW10a, MW10b, MW10c and EW1 on December 13,
<br /> 2004.
<br /> The water level data were used to develop the groundwater elevation contour maps for the
<br /> shallow (A), intermediate (B), and deep (C) groundwater zones (Figures 3 through 5). MW 1
<br /> through MW6a, MW7a, MW9a, MW 10a, and EW 1 are screened in the shallow water-bearing
<br /> zone. Water levels in these wells ranged from 66.27 to 67.37 feet below the tops of the well
<br /> casing (TOC) elevation. Groundwater in the shallow zone beneath the site flowed towards the
<br /> East-Southeast during the December 13, 2004 groundwater-monitoring event. The average
<br /> • hydraulic gradient in the shallow water-bearing zone on December 13, 2004, was calculated to be
<br /> 0.0002 ft/ft or approximately 1.1 ft/mile.
<br /> MW6b, MW7b, MW9b and MWIOb are screened in the intermediate water-bearing zone. Water
<br /> levels in MW6b, MW7b and MW 10b ranged from 66.61 to 66.71 feet below TOC elevation.
<br /> The water level in MW9b was under pressure and DTW ranged from 73.48 to 72.75 feet below
<br /> TOC. Groundwater in the intermediate zone beneath the site flowed towards the Southeast during
<br /> the December 13, 2004 groundwater-monitoring event. The average hydraulic gradient in the
<br /> shallow water-bearing zone on December 13, 2004, was also calculated to be 0.013 ft/ft or
<br /> approximately 68 ft/mile.
<br /> MW6C, MW7c, MW8, MW9c and MWIOc are screened in the deep water-bearing zone. Water
<br /> levels in these wells ranged from 66.11 to 67.88 feet below TOC elevation. Groundwater in the
<br /> deep zone beneath the site flowed towards the East-Southeast during the December 13, 2004
<br /> groundwater-monitoring event. The average hydraulic gradient in the shallow water-bearing zone
<br /> on December 13, 2004, was also calculated to be 0.0005 ft/ft or approximately 2.6 ft/mile.
<br /> A summary of groundwater monitoring data is presented in Table 1.
<br /> 2.2 Groundwater Analytical Results
<br /> The groundwater samples collected from MW1 through MW3, MW5, MW6a and EW1
<br /> contained detectable concentrations of TPHg. The groundwater samples collected from MW5
<br /> contained detectable concentrations of TPHg but no BTEX constituents. All BTEX constituents
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