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. 23 May 1996 <br /> AGE-NC Project No 95-0132 <br /> Page 2 of 5 <br /> 2 3 MONITORING WELL INSTALLATION <br /> On 3 February 1993, one 2-inch diameter ground water monitoring well (MW-1) was installed at the <br /> Isite The location of the well is depicted in Figure 2 Low concentrations of total petroleum <br /> hydrocarbons quantified as diesel (TPH-d) was detected in the initial water sample In quarterly <br /> ground water monitoring during May 1993, petroleum hydrocarbons were not detected in any ground <br /> water samples, but in August 1993, diesel and benzene were detected at monitoring well MW-1 <br /> On 27 January 1995, two additional ground water morutoring wells (MW-2 and MW-3) were <br /> installed at the site Petroleum hydrocarbons were not detected in soil samples collected from either <br /> well <br /> All morutonng wells were sampled in February and November 1995 TPH-d was again detected in <br /> the ground water sample collected from MW-1 <br /> I <br /> 2 4 GROUND WATER DEPTH AND GRADIENT <br /> The water-table surface occurs at a depth of approximately 15 feet below surface grade (bsg) at the <br /> site under unconfined conditions With depth, the aquifer(s)become confined due to the presence of <br /> heterogeneous layers of sediment <br /> Ground water surface elevation contour maps, published by the San Joaquin County Flood Control <br /> Iand Water Conservation District, show the regional ground water flow direction to be towards the <br /> northeast <br /> 1 <br /> 3.0. QUARTERLY MONITORING AND SAMPLING PROCEDURES <br />' 3 l MONITORING WELL PURGE PROCEDURES <br />' On 09 April 1996, the depth to ground water and total depth in each well was measured to the <br /> nearest 0 01 foot, relative to the top of the well casing, using a Solinst water level meter The ground <br /> water surface elevation in each well was calculated by subtracting the measured depth to ground <br />' water from the relative reference point elevation marked on the top of the well casings (Table 1) <br /> The ground water surface elevation for each well was plotted on a scaled site map, and was used to <br />' generate the ground water surface elevation contours (Figure 3 -Relative Ground Water Elevation) <br /> After water levels were measured, approximately 7 5 gallons of water (a minimum of three well <br /> volumes)were purged from MW-1 and MW-3 utilizing a two-stage submersible pump By agreement <br /> 1 <br />