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hydrocarbons in the monitoring wells in the past but have decreased to nondetectable levels with continued operation of the vapor extraction system (Table 1) GROUNDWATER SAMPLING AND GRADIENT EVALUATION RESNA personnel performed the latest quarterly groundwater monitoring of monitoring wells on December 29, 1994. At the direction of SJCPHS in a conversation on July 14, 1994, the number of wells to be sampled was decreased from six to three Field work consisted of ' measuring depth-to-water (DTV) levels in all wells, collecting groundwater samples from wells MW-1, MW-3, and MW-4, and submitting groundwater samples for laboratory analysis ' Water level measurements were collected from wells MW-1 through MW-6 The depth to water ranged from 65 34 to 65 97 feet below top of well casing elevation Groundwater elevations have increased an average of 1 80 feet since September 9, 1994 The water level data were used to develop the groundwater elevation contour map (Plate 3) Assuming that horizontal isotropic conditions prevail, groundwater in the uppermost aquifer beneath the site flowed in a northeasterly direction. The hydraulic gradient on December 29, 1994 was calculated to be ' 0 001 ft/ft or about 7 feet/mile These data indicate a slight change in gradient direction but no change in magnitude when compared with the previous quarterly monitoring results A summary of groundwater monitoring data is presented in Table 2 Groundwater elevations are referenced to feet mean sea level Groundwater samples were collected from three shallow groundwater monitoring wells, MW-1, MW-3, and MW-4 Prior to collection of groundwater samples a minimum of three well casing volumes were purged The depth-to-water, pH, electrical conductivity, and temperature were ' measured and allowed to stabilize before groundwater samples were collected No evidence of measurable floating product or hydrocarbon vapor was noted in the water samples Samples were then collected from each well using disposable bailers Purge water was contained in 55 ' gallon DOT approved drums and stored on-site pending proper disposal Purge water from previous sampling event did not contain detectable concentrations of petroleum hydrocarbons and was discharged to the ground surface The groundwater samples collected from each well were submitted with Chain of Custody Record to Sequoia Analytical Laboratories, a State Certified laboratory (FLAP #1210) Samples ' were analyzed for total petroleum hydrocarbons as gasoline (TPHg), total petroleum hydrocarbons as diesel (TPHd), and benzene, toluene, ethylbenzene, and total xylenes (BTEX) utilizing EPA methods 8015/8020 Groundwater well purge and sample logs are provided in Appendix A 54W561QUARTLYI4QMR1994 FNL 2 C:anonieEnvlronmental