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5.2 Water Samples <br /> IOn April 23, 1993, Murray & Associates collected rou duplicate p groundwater samples from <br /> the four newly installed monitoring wells Each sample was evaluated for total petroleum <br /> hydrocarbon constituents and volatile aromatic compounds The results of these analyses <br /> are summarized in Table 2. Complete analytical reports are presented in Appendix 4. <br /> Included in Table 2 are the relative State or EPA Action levels for each of the constituents <br /> analyzed <br /> Table 2 <br /> ' Analytical Results -- Water Samples <br /> Constituents Sample ID State <br /> u Action <br /> MW-1 MW-2 MW-3 MW-4 Levels MCL <br /> ' Benzene 17,000 ND 17,000 15 07 5 <br /> Toluene 39,000 ND 16,000 ND 100 2,000 <br /> Ethylbenzene 4,900 ND 1,600 ND 680 680 <br /> Xylene 25,000 ND 12,000 ND 620 440 <br /> Total Pet Hyd. 180,000 400 83,000 ND - - <br /> ' ND = Not detected <br /> MCL = EPA Drinking Water Standards and goals for Maximum Contaminant Levels <br /> High concentrations ofetroleum hydrocarbon P y products were found in two of the four <br /> newly installed groundwater monitoring wells Although, MW-1 was initially considered <br /> to be the up-gradient well, the direction of groundwater flow as shown in Figure 4, appears <br /> to have nearly reversed itself since completion of our initial subsurface investigation in <br /> April, 1992 The current direction of groundwater flow appears to be toward the <br />' southeast, perhaps as a result of large volume pumping from the City of Lathrop's four <br /> municipal wells, located approximately 1-mile south east of the Langston property (Figure <br /> 5). This change in groundwater flow direction coupled with heavy seasonal rainfall over <br /> the past year has resulted in a change in the configuration and size of the plume of <br /> 15 <br /> 1 <br />