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A S S O C I A T E S I INI C
<br /> monitonng wells and two of the soil bonngs were completed as vapor extraction wells The soil
<br /> boring, groundwater monitoring well, and vapor extraction well locations are shown on Figure 2
<br /> On July 3, 1997, the monitoring wells were developed and sampled for petroleum hydrocarbons
<br /> along with the adjacent property owner's well (CW) The samples from wells MW1, MW2, and
<br /> MW3 contained concentrations of total petroleum hydrocarbons as gasoline (TPHg) and benzene
<br /> ranging from 3,200 parts per billion (ppb) to 130,000 ppb and 920 to 11,000 ppb, respectively
<br /> Field activities and analytical results were detailed in Smith Technology's Summary Report dated
<br /> September 17, 1997
<br /> On March 24 and 25, 1998, ATC personnel supervised advancement of seven soil bonngs, ASB 1,
<br /> MW4, MW5, MW6, MW7, SB8, and SB9, at the site to depths ranging from approximately 26 5
<br /> to 62 feet bgs at the project site to 1) evaluate the horizontal and vertical extent of petroleum
<br /> hydrocarbon impacted soil and groundwater, 2) determine and define soil stratigraphy, and 3)
<br /> install groundwater monitoring wells (MW4, MW5, MW6, and MW7) within the uppermost
<br /> aquifer Groundwater samples collected from wells MW5, MW6, and MW7 contained elevated
<br /> concentrations of TPHg and benzene Field activities and analytical results were detailed in
<br /> ATC's Summary Report of Subsurface Investigation, dated August 14, 1998
<br /> SAMPLING ACTIVITIES
<br /> • On December 17, 1998, groundwater samples were collected by ATC Associates personnel from
<br /> monitoring wells MW 1 through MW7 and CW The locations of the monitoring wells are shown
<br /> on Figure 2 Prior to collection of groundwater samples, the depth to water, pH, electncal
<br /> conductivity, and temperature were measured in the monitoring wells and recorded A minimum
<br /> of three well casing volumes were purged from each well prior to sampling The wells were
<br /> allowed to recover and samples were collected from each well using dedicated disposable bailers
<br /> The groundwater samples collected from each well were submitted to State-certified Sequoia
<br /> Analytical (FLAP Cert No 12 10) for chemical analysis of TPHg, benzene, toluene, ethylbenzene,
<br /> and xylenes (BTEX) utilizing EPA methods 8015/8020 Groundwater well purge and sample logs
<br /> are contained in Attachment 1
<br /> ANALYTICAL RESULTS
<br /> TPHg and BTEX were detected above laboratory method detection limits in the samples collected
<br /> from wells MW1, MW2, MW3, MW5, and MW7, and TPHg was detected above laboratory
<br /> detection limit in the sample collected from .well MW6 The samples collected from wells MW4
<br /> and CW contained no detectable concentrations of petroleum hydrocarbons MTBE was detected
<br /> in samples from wells MW2, MW4, MW7, and CW, however these detections were not
<br /> confirmed by laboratory EPA method 8260 Previous groundwater samples were analyzed for
<br /> fuel oxygenates utilizing EPA method 8260 and none were detected indicating the recent
<br /> detection of MTBE is most likely a false positive due to chromatogram interference A summary
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