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f <br /> A S S O C I A T E S I N C <br /> GROUNDWATER FLOW DIRECTION <br /> Groundwater level measurements were collected from MW-1 through MW-6 on April 14, 2003 <br /> Groundwater levels ranged from 26 24 to 27 10 feet below the tops of the well casings, <br /> representing an average increase in the water table elevation of approximately 0 15 feet since <br /> January 2003 The water level data were used to develop the groundwater elevation contour map <br /> (Figure 3) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost <br /> aquifer beneath the site flowed generally towards the east with an apparent slight depression in the <br /> vicinity of the former UST area The average hydraulic gradient on April 14, 2003 was calculated <br /> to be 0 0006 ft/ft or approximately 3 4 ft/mile A summary of groundwater monitoring data is <br /> presented in Table 1 <br /> CONCLUSIONS <br /> Concentrations of petroleum hydrocarbon constituents decreased in the groundwater sample <br /> collected from MW-3 during the second quarter 2003 below levels measured during recent <br /> quarterly monitoring events The concentrations of petroleum hydrocarbon constituents detected <br /> in the groundwater sample collected from MW-3 during the second quarter 2003 represent <br /> historically low concentrations for groundwater samples collected from this well Low <br /> . concentrations of ethylbenzene, total xylenes, and TPHg were detected in the groundwater <br /> sample collected from MW-2 Concentrations of petroleum hydrocarbons remained at <br /> nondetectable levels in groundwater samples collected from MW-1, MW-4, MW-5, and MW-6 <br /> The direction of groundwater flow and magnitude of the hydraulic gradient are generally <br /> consistent with previous quarters <br /> RECOMMENDATIONS <br /> ATC recommends quarterly groundwater monitoring continue for the third quarter 2003 <br /> Please contact our office at (209) 579-2221 if you have any questions or comments <br /> Respectfully submitted, <br /> ATC Associates Inc <br /> Todd C Hafner ean�Homsey, P E <br /> Project Geologist CA Registered Civ 47410 <br /> 1, <br /> ,�'fie, <br /> • cc Gerald Thiemannl `; <br /> Jim Barton, RWQCB a , <br /> w Iwordpro1626051quan1yl2QR-2003 doc 3 <br /> C_ a <br /> a�- f . a <br />