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Mr Terry Tarditi July 12, 2005 Page 3 Laboratory reports for the groundwater samples collected for these sampling events are included as Attachment B Analytical laboratory Kiff Analytical,Inc, Davis, California (California Department of Toxic Substances Control Certification No 2336) Sample exceptions None Shallow groundwater gradient Flat Shallow groundwater flow direction N/A Average depth-to-water 69 64 feet Average change in shallow groundwater elevation from 4th qtr (2004) to 1�, qtr (2005) -0 52 feet DISCUSSION Based on the second quarter's data, the groundwater hydraulic gradient remains • relatively flat, a reasonable hydraulic gradient could not be measured, as shown in Figure 2 Tlus flat hydraulic gradient is helping retard further lateral migration of constituents of concern originally documented by the field investigation results summarized in BC's Subsurface Investigation Results and Site Conceptual Model, June 28, 2004 The on-site supply well has been sampled on a quarterly basis since November 2002 and has never contained any detectable concentrations of any constituents of concern Therefore, sample results from this well are not included in the discussions below In addition, concentrations of 1,2-DCA and EDB have not been detected and are not included in the discussion below BTEX The reporting limits for all constituent concentrations in MW-1 were diluted due to known high concentrations of MtBE The dilutions were necessary because the MtBE concentrations were out of the calibration range for the target constituent The reporting limits remained the same for wells MW-2, MW-3 and MW-4 at 0 5 micrograms per liter (µg/L) BTEX concentrations were below their respective reporting limits in all of the wells consistent with previous quarters Per the PHS/EHD's request, BC has worked with the analytical laboratory to determine when it is feasible to quantify the BTEZ. constituents without damaging the equipment, especially in samples from MW-1 • T6zr rrport uar prepared to actordanrr unth the rlandardr of the enrrronmenial,onrmltzng radufit)at the lane it rvurpreparrd It rhould not be retied upon by pastier other lban More for idiom it war prepared and leen oil)to the extent of the nope of uvrk ulmb uxrr aalhars,'d Tbrr report doer not gmararalee ilial no addiiionalenrxronmenta!contamination Ge}and that derirzhedin lhz,report evrt,tit t/e rite P\27000\127960 r&1 Trucking GW Aimutonng 2005\Rc-port~\2nd-05ytr doc