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t 4 In August 1993, wells MW-1, MW-2, and MW-3 were monitored and sampled. Analytical results showed that MW-1 had no measurable concentrations of petroleum hydrocarbons in the groundwater. Weiss MW-2 and MW-3 contained detectable levels of petroleum hydrocarbons. A program of quarterly groundwater monitoring and sampling was begun in March 1994. In August 1995, Smith Environmental conducted a subsurface site investigation to further define the extent of contamination in groundwater at the site. Smith Environmental supervised the installation of monitoring wells MW-4, MW-5 and MW-6. These three new wells were developed and sampled along with monitoring wells MW-1, MW-2, and MW-3. Analytical results of groundwater samples f from the six monitoring wells indicated the presence of elevated concentrations of petroleum hydrocarbons in the vicinity of wells MW-3 and MW-6, on the northeast corner of the site. SAMPLING ACTIVITIES On October 23, 1996, groundwater samples were collected by Smith Technology personnel from monitoring wells MW-1 through .MW-6. The locations of the.monitoring wells are shown on Figure 2. Prior to coIIection of groundwater samples, the depth to water, pH, electrical conductivity, and temperature were measured in the monitoring wells and recorded. A minimum of three well casing volumes were purged from each well prior to sampling. The wells. were allowed to recover and samples were collected from each well using dedicated disposable bailers. The groundwater samples collected from each well were submitted to Argon Mobile Laboratories (FLAP cert. no. 1873) for analysis of total petroleum hydrocarbons as gasoline (TPHg), benzene, toluene, ethylbenzene, xylenes (BTEX), and methyl-tertiary-butyl-ether (MTBE) utilizing EPA - methods 801518020. Groundwater well purge and sample logs are provided in Attachment I. ANALYTICAL RESULTS Petroleum hydrocarbon constituents were detected above laboratory method detection limits in the samples collected' from both wells sampled. The samples collected from wells MW-3 and MW-6 contained TPHg at concentrations of 79,000 micrograms per liter [ug/1] and 1,500 ug/l, respectively. MTBE was not detected in any of the wells although well MW-3 had a higher detection limit due to dilution factors. A summary of analytical results is presented in Table 1. Laboratory data sheets and chain-of-custody documentation are provided in Attachment 1T. GROUNDWATER FLOW DIRECTION Water level measurements were collected from wells MW-1, MW-2, MW-3, MW-4, MW-5 and MW-6 on October 23, 1996. Water levels ranged from 2596 to 26.70 feet below the tops of the well ,casing elevations, representing an average decrease ' in the water table elevation of approximately 2.33 feet since July 1996. 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 towards the southeast with a w:W43731quw t1y14gr-1996Aoc 2 . • SMTH