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' The groundwater samples collected from each well were submitted to State-certified Argon
<br /> Laboratories Inc. (Environmental Laboratory Accreditation Program Cert, No. 2359) in Ceres,
<br /> California for chemical analyses of total petroleum hydrocarbons as gasoline (TPHg) and total
<br /> tpetroleum hydrocarbons as diesel (TPHd) utilizing Environmental Protection Agency (EPA)
<br /> Method 801513; benzene, toluene, ethylbenzene, and xylenes (BTEX) utilizing EPA Method
<br /> 802113; and methyl tertiary butyl ether (MTBE), ethyl tertiary butyl ether (ETBE) di-isopropyl
<br /> ' ether (DIPS), 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 MW1 through MW5, MW6a, MW6b, MW6c, MW7a, MW7b,
<br /> MW7c, MW8, MW9a, MW9b, MW9c, MW10a, MW10b, MW1Oc and EW1 on September 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). Water
<br /> levels in MW1 through MW6a, MW7a, MW9a, MW10a, and EW1, screened in the shallow
<br /> water-bearing zone, ranged from 6 6.8 3 to 67.50 feet below the tops of the well casing elevations.
<br /> Groundwater
<br /> in the shallow water-bearing zone beneath the site flowed towards the east during
<br /> the September 13, 2004 groundwater-monitoring event. The average hydraulic gradient in the
<br /> ' shallow water-bearing zone on September 13, 2004, was calculated to be 0.0003 ft/ft or
<br /> approximately 1.6 ft/mile. A summary of groundwater monitoring data is presented in Table 1.
<br /> ' 2.2 Groundwater Analytical Results
<br /> The groundwater samples collected from wells MW1 through MW4, and EW1 contained
<br /> detectable concentrations of TPHg and BTEX constituents. The groundwater samples collected
<br /> from wells MW5 and MW6a contained detectable concentrations of TPHg but no BTEX
<br /> constituents. None of the groundwater samples contained detectable concentrations of TPHd.
<br /> Groundwater samples collected from MW 1, MW2, MW4, MW5, MW6a, MW6b, MW6c, MW7,
<br /> MW7b, MW7c, MW8, MW10b and EW1 contained detectable concentrations of MTBE. The
<br /> ' groundwater sample collected from well MW2 contained a detectable concentration of TBA.
<br /> Groundwater samples collected from wells MW1, MW2, MW4, MW6b, MW7a, MW7b, MW7c,
<br /> ' MWIOb, and EW1 contained detectable concentrations of 1,2-DCA. - - --
<br /> Analytical results of groundwater samples are summarized in Table 2. Laboratory data sheets and
<br /> chain-of-custody documentation are contained in Attachment 2. Isoconcentration maps depicting
<br /> the TPHg and benzene are presented in Figures 6 and 7, respectively. MTBE concentrations in
<br /> the A, B, and C water bearing zones are presented in Figures 8, 9 and 10, respectively.
<br /> ' S:1268231QM reports\2004 3QR.doc 3 ATC Associates Inc.
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