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v OLTC A S S O C I A T E S I N C groundwater samples from all wells, and submitting groundwater samples for laboratory analyses. Water level measurements were collected from groundwater monitoring wells MW-1 through MW-6. The depth to water ranged from 7.58 to 9.28 feet below top of well casing elevation. Groundwater elevations have decreased an average of 1.10 feet since the previous quarterly monitoring event conducted in June 2002. The water level data were used to develop the groundwater elevation contour map (Figure 2). Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed in a northerly direction. The average hydraulic gradient on January 12, 2004, was calculated to be approximately 0.003 ft/ft or approximately 16 feet/mile. The data indicate a groundwater gradient that is generally consistent with previous groundwater gradients observed at the site. A summary of groundwater monitoring data is presented in Table 1. Groundwater elevations are referenced to feet above mean sea level. Groundwater samples were collected from monitoring wells MW-1 through MW-6. Prior to collection of groundwater samples a minimum of three well casing volumes were purged. The pH, electrical conductivity, and temperature were measured and allowed to stabilize before groundwater samples were collected. Samples were then collected from each well using disposable bailers. Purge water was contained in 55-gallon DOT approved drums. Groundwater `., well purge and sample logs are provided in Appendix A. The groundwater samples collected from each well were submitted with Chain of Custody Record to State-certified Argon Laboratories Inc. (ELAP Cert. No. 2359). The samples were analyzed for TPHg by EPA Method 801513; BTEX by EPA Method 802113; and MTBE, tert- amyl methyl ether (TAME), TBA, di-isopropyl ether (DIPE), ethyl-tert-butyl ether (ETBE), 1,2- dichloroethane (1,2-DCA), and 1,2-dibromoethane (EDB) by EPA Method 826013. RESULTS OF LABORATORY ANALYSES The laboratory analytical results indicate petroleum hydrocarbons were detected in the groundwater samples collected from monitoring wells MW-2 and MW-3. TPHg, BTEX, and MTBE were detected in the sample collected from MW-2 at concentrations of 500 micrograms per liter (µg/1), 200 µg/1, 2.1 µg/l, 3.6 µg/1, 1.9 µg/1, and 10 µg/1, respectively. TPHg, benzene, and ethyl benzene were detected in the sample collected from MW-3 at concentrations of 600 µg/1, 180 pg/1, and 45 gg/l, respectively. Petroleum hydrocarbons were not detected at or above the laboratory reported detection limits in the groundwater samples collected from monitoring wells MW-1, MW-4, MW-5, and MW-6. EDB and 1,2-DCA were not detected at or above the laboratory reported detection limit in any of the groundwater samples. Groundwater analytical results are summarized in Table 2. The laboratory analytical reports are included in Appendix B. `r V sAEnvironmenta1\1 786 1\reports\1 gmr2004.doc 3