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<br /> • A S S O C I A T E S I N C
<br /> ' In 1993, soil borings MW3 MW4, and VW1 contained detectable concentrations of
<br /> TPHg and benzene at depths of 21 feet bgs Soil samples collected in 1995 from borings
<br /> ' AS1, PI, P3, and P4 contained detectable concentrations of TPHg and benzene at depths
<br /> of 10, 15, and 20 feet bgs Groundwater samples collected from wells MW1, MW3, and
<br /> ' MW4 have historically exceeded the Department of Health Services Maximum
<br /> Contaminant Level (MCL) for benzene However, concentrations of benzene in these
<br /> wells have decreased to concentrations below laboratory detection limits Historically,
<br /> benzene has not been detected in groundwater samples collected from wells MW2, MW5,
<br /> ' MW6, and MW7, or has only been detected at very low concentrations Fuel oxygenates
<br /> �f
<br /> have been detected in wells MW1, MW2, MW3, MW4, MW5, MW6, and MW7
<br /> 1 However, MTBE has been detected intermittently in wells MW2, MW3, MW4, MW5,
<br /> and MW6 and has been detected consistent) in MW1 in which concentrations have � Ty
<br /> �r '" decreased from 80 u 1 to below detection limits?
<br /> Pot- g/ The surface of the site ><s concrete or
<br /> ' paved with asphalt, which will hinder the migration of contaminants in the source area
<br /> caused by rain or surface washing from the soil to the groundwater Therefore, the
<br /> likelihood of contaminants in the vadose zone reversing or threatening to reverse the
<br /> ' mass reduction rate of groundwater pollutants is expected to be very low n n c t-�'I ica It el s.
<br /> Criterion 4: There are no existing water supply wells, surface waters or other receptors
<br /> threatened by the remaining contaminants in soil or groundwater.
<br /> A well survey for the site was performed by SEACOR in 1994 According to this well
<br /> ' survey, well 1N46E/4J2, located approximately 250 feet to the north, is the closest
<br /> domestic well/to the site However, this well is located in a hydrologically upgradient
<br /> direction from the site and according the EHD, the well has been abandoned The nearest
<br /> ' surface water, the Stockton Deep Water Channel is located approximately 1,400 feet to
<br /> the south, in an assumed crossgradzent direction For the investigation, groundwater
<br /> wells were installed only in the shallowest aquifer Laboratory analytical data from the
<br /> ' most recent groundwater sampling, conducted in November 2003, indicated that there
<br /> were no detectable concentrations of TPHg or BTEX compounds in wells MW2, MW5,
<br /> and MW6 Therefore, the likelihood of pollutants remaining in the aquifer threatening
<br /> wd t —o f Co--St f
<br /> these potential receptors is expected to be very low M-7---y lcis1!Y'
<br /> pra_3.r...eJ �"'"`�""`°r"�-Lclf c��; dJF„+d�• r�rxeJu'�,.d.
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<br /> Criterion 5: Pollutants remaining in groundwater do not create or threaten to create risk
<br /> l to human health and safety, or to future beneficial use(s) of groundwater
<br /> Patterns of existing and future demands for usable water resources in the
<br /> ' area must be considered in determining what period of time is reasonable to
<br /> reach non-detectable (or background) concentrations.
<br /> t As discussed in Criteria 4, there are no potential water supply wells, surface waters, or
<br /> other receptors located within 1,400 feet of the site The entire site is surfaced with
<br /> asphalt effectively limiting the exposure of the public to potential soil vapors Therefore
<br /> w 1271421reportslclosure doe 21
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