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groundwater Wells MW-2 and MW-3 contained detectable levels of petroleum hydrocarbons A <br /> �' P Y <br /> ` program of quarterly groundwater monitoring and sampling was begun in March 1994 <br /> In August 1995, Smith Environmental conducted a subsurface site investigation to further define the <br /> extent of contamination in groundwater at the site Smith Environmental supervised the installation of <br /> monitoring wells MW-4, MW-5 and MW-6 These three new wells were developed and sampled <br /> along with monitoring wells MW-1, MW-2, and MW-3 Analytical results of groundwater samples <br /> from the six monitoring wells indicated the presence of elevated concentrations of petroleum <br /> hydrocarbons in the vicinity of wells MW-3 and MW-6, on the northeast corner of the site <br /> SAMPLING ACTIVITIES <br /> On April 1, 1997, groundwater samples were collected by Smith Technology personnel from <br /> monitoring wells MW-3 and MW-6 The locations of the monitoring wells are shown on Figure <br /> 2 Prior to collection of groundwater samples, the depth to water, pH, electrical conductivity, and <br /> temperature were measured in the monitoring wells and recorded A minimum of three well <br /> casing volumes were purged from each well prior to sampling The wells were allowed to recover <br /> and samples were collected from each well using dedicated disposable bailers <br /> The groundwater samples collected from each well were submitted to Argon Mobile Laboratories <br /> (FLAP cert no 1873) for analysis of total petroleum hydrocarbons as gasoline (TPHg), benzene, <br /> toluene, ethylbenzene, xylenes (BTEX), and methyl-tertiary-butyl-ether (MTBE) utilizing EPA <br /> methods 8015/8020 At the request of Ms Mary Meays of San Joaquin County Public Health <br /> Services Environmental Health Division (PHS/EHD), a duplicate sample was also collected from <br /> MW-3 and submitted to GTEL Environmental Laboratory (ELAP cert no 1845) for analysis of <br /> TPHg, BTEX, and MTBE Groundwater well purge and sample logs are contained in <br /> Attachment 1 <br /> ANALYTICAL RESULTS <br /> Petroleum hydrocarbon constituents were detected above laboratory method detection limits in <br /> the samples collected from well MW-3 The sample collected from well MW-6 contained no <br /> petroleum hydrocarbons above the method detection limit MTBE was not detected in well MW- <br /> 3, although it had a higher detection limut due to dilution factors A summary of analytical results <br /> is presented in Table 1 Laboratory data sheets and chain-of-custody documentation are provided <br /> in Attachment 2 <br /> GROUNDWATER FLOW DIRECTION <br /> Water level measurements were collected from wells MW-1, MW-2, MW-3, MW-4, MW-5 and <br /> MW-6 on April 1, 1997 Water levels ranged from 18 71 to 19 54 feet below the tops of the well <br /> casing elevations, representing an average increase in the water table elevation of approximately <br /> 2 73 feet since January 1997 Groundwater elevations have increased to the highest levels since <br /> w 1943731quartiyl2gr-1997 doe 2 <br /> • <br /> s�m <br />