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z Mr Mike Infiurna Page 2 • well MW1D was 56 63 feet btoc Water level data are summarized in Table 1 Monitoring well locations are shown on Figure 2 Field data sheets are included in Attachment A Groundwater elevation was determined in each well by subtracting the depth to groundwater measurement from the respective surveyed wellhead elevation On June 9, the potentiometric surface of the A Zone wells ranged from 37 18 feet to 37 22 feet below mean sea level (MSL) The potent>ometrnc surface of the B Zone wells ranged from 37 07 feet to 37 28 feet below MSL The potent>ometric surface in C Zone well MW1D was 37 17 feet below MSL Due to the complexity of the well depthlpotentiometric surface relationship, groundwater gradient was interpreted in several ways Figure 3 interprets the gradient using data from the A and B Zone wells together Flow is toward the north-northwest at a gradient of approximately 0 0008 ft/ft Potentiometric surface maps utilizing data from the A and B Zones separately are depicted on Figures 4 and 5, respectively Flow in the A Zone is interpreted to be toward the east and northeast at a gradient of approximately 0 001 ft/ft while flow in the B Zone is toward the northwest at approximately 0 0008 ft/ft Note that an alternative interpretation for the A Zone would have flow toward the northwest Groundwater Sampling On June 9 and 10, 2004, the site wells were purged and sampled During purging, temperature, pH and electrical conductivity parameters were measured Purging continued until these M parameters had stabilized A minimum of three well casing volumes was purged from each well Purge water was contained in appropriately labeled DOT-approved 55-gallon drums Purge logs are included in Attachment A Groundwater samples were collected after adequate groundwater recovery Samples were collected in sealed, preserved VOAs and stored in an ice chest refrigerated to a temperature of approximately 4°C Samples were delivered under chain of custody protocol to Argon Laboratories (ELAP #2359) Sample analysis consisted of gasoline oxygenate additives, 1,2-DCA and EDB using EPA Method 8260B, BTEX using EPA Method 8021B, and TPHg using modified EPA Method 8015B GROUNDWATER ANALYTICAL RESULTS TPHg and BTEX compounds were not detected in the samples from wells MW5 and MW7 TPHg was detected in the samples from the rest of the wells at concentrations ranging from 250 to 85,000 parts per billion (ppb) Benzene levels in these wells ranged from 1 6 ppb in MW3 to 14,000 ppb in well MW 1 Analytical results are summarized in Table 2 Attachment B contains laboratory reports and chain of custody documentation Gasoline oxygenates and additives were not detected in wells MW3, MW5, and MW7 1,2-DCA was detected in each of the other wells at concentrations ranging from 15 ppb in MW 1 D to 1,800 ppb in MW1 A concentration of 2 5 ppb MTBE was reported in the sample collected from well MW1D, however, this result is suspect No other oxygenates or additives were detected 11GZA—FSIVOL_11DATA\GROUNDZEIHARRYS\Reports\QMR1200412QM2004a doc