|
i
<br /> i
<br /> DCA), and 1,2-dibromo ethane (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 MWI through MW5, MW6a, MW6b, MW6c, MW7a, MW7b,
<br /> MW7c, MW8, MW9a, MW9b, MW9c, MW1Oa, MWIOb, MWIOc and EW1 during the June 21-
<br /> 22, 2005 monitoring event The water level data were used to develop the groundwater elevation
<br /> contour maps for the shallow (A), intermediate (B), and deep (C) groundwater zones (Figures 3
<br /> through 5)
<br /> MWI through MW6a, MW7a, MW9a, MW10a, and EW1 are screened in the shallow water-
<br /> bearing zone During the June 21-22, 2005 event, water levels in these wells ranged from 63 78
<br /> to 65 13 feet below the tops of the well casing (TOC) elevation Groundwater in the shallow
<br /> zone beneath the site flowed towards the northeast during the June 21-22, 2005 groundwater-
<br /> monitoring event The average hydraulic gradient in the shallow water-bearing zone during the
<br /> June 21-22, 2005 monitoring event was calculated to be 0 002 ft/ft or approximately 10 6 ft/mile
<br /> MW6b, MW7b, MW9b and MW1Ob are screened in the intermediate water-bearing zone Water
<br /> levels in MW6b, MW7b, MW9b, and MW1Ob ranged from 64 58 to 65 90 feet below TOC
<br /> • elevation Groundwater in the intermediate zone beneath the site flowed towards the south during
<br /> the June 21-22, 2005 groundwater-monitoring event The average hydraulic gradient in the
<br /> shallow water-beanng zone during the June 21-22, 2005 event was also calculated to be 0 0004
<br /> ft/ft or approximately 2 1 ft/mile
<br /> MW6c, MW7c, MW8, MW9c and MW10c are screened in the deep water-bearing zone Water
<br /> levels in these wells ranged from 64 08 to 66 06 feet below TOC elevation Groundwater in the
<br /> deep zone beneath the site flowed towards the southeast during the June 21-22, 2005 groundwater-
<br /> monitoring event The average hydraulic gradient in the shallow water-bearing zone during the
<br /> June 21-22, 2005 monitoring event was also calculated to be 0 001 ft/ft or approximately 5 3
<br /> ft/mile
<br /> A summary of groundwater monitoring data is presented in Table 1
<br /> 2.2 Groundwater Analytical Results
<br /> The groundwater samples from the June 21-22, 2005 monitoring event in MWI, MW2, MW3,
<br /> MW5,MW6a and EW1 contained detectable concentrations of TPHg BTE and/or X constituents
<br /> were detected in samples from MWI, MW2, MW3 and EW1 None of the groundwater samples
<br /> contained detectable concentrations of TPHd
<br /> • MTBE was detected in groundwater samples from MWI, MW2, MW4, MW5, MW6a, MW6b,
<br /> MW6c, MW7a, MW7b, MW7c, MWIOa, MW10b and EW1 The groundwater samples from
<br /> MW2 and MW6a contained detectable concentrations of TBA Groundwater samples from
<br /> S 1268231QM reports\2005 2ndQR doc 3
<br />
|