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<br /> A S S 8 C I A T E S I N C
<br /> and TPHg concentrations in shallow groundwater in September 2001 are shown on Figures 6 and
<br /> 8, respectively
<br /> The groundwater samples collected in December 2001 from groundwater monitoring. wells
<br /> MW5, MW9, and MW10 contained no detectable concentrations of TPHg, BTEX, MTBE,
<br />' TAME, ETBE, DIPE, TBA, 1,2-DCA, or EDB The groundwater samples collected from
<br /> groundwater monitoring wells MW4, MW7, and MW8, drinking water well DW, air sparge well
<br />'
<br /> ASI, and piezometers AS 1(s) and AS 1(d) contained detectable concentrations of TPHg and
<br /> BTEX, but contained no detectable concentrations of MTBE, TAME, ETBE, DIPE, TBA, 1,2-
<br /> DCA, or EDB The groundwater samples collected from groundwater monitoring wells MW1,
<br />' MW3, MW6, and piezometers PZ 1 a(s), PZ 1 a(d), and PZ 1 b(d) contained the highest
<br /> concentrations of TPHg and BTEX, but contained no detectable concentrations of MTBE,
<br /> TAME, ETBE, DIPE, TBA, 1,2-DCA, or EDB Isoconcentration maps depicting the benzene
<br /> and TPHg concentrations in shallow groundwater in December 2001 are shown on Figures 7 and
<br /> 9, respectively
<br />' Analytical results of groundwater samples are summarized in Table 2 Laboratory data sheets
<br /> and chain-of-custody documentation for groundwater samples are contained in Appendix D
<br /> 5.0 VAPOR EXTRACTION PILOT TEST
<br /> A vapor extraction pilot test was performed in accordance with ATC's Workplan for Vapor
<br />' Extraction and Air Sparge and Pilot Testing at Pacific Coast Recreation, 3755 Munford Avenue,
<br /> Stockton, California, dated June 27, 2001 The purpose of this test was to evaluate vapor
<br />' extraction as a viable remedial option for impacted soil and groundwater at the site and to collect
<br /> data to design a vapor extraction system 0111 el
<br /> ' 5.1 Vapor Extraction Test Methods and Procedures eve
<br /> On October 31 and November 1, 2001, ATC performed a short-term vapor extraction test and a
<br />' long-term vapor extraction test, respectively On the first day, a shortzterm vapor extraction test
<br /> was performed by ATC using vapor well VW2 as the vapor extraction point while monitoring
<br /> vacuum response in the surrounding wells, MW1, MW2, MW3, MW$, ASI, AS1(d), PZla(s),
<br /> ' PZ 1 a(d), PZ 1 b(s), PZ 1 b(d), V W 1 and V W3 (Figure 3) The test was approximately 2 hours in
<br /> length Flowrates, applied vacuums, influent and effluent VOC concentrations, and temperatures
<br /> were also monitored during the test Vapors were extracted using an internal combustion (IC)
<br /> engine equipped with a 5-hp blower and a moisture knockout chamber Two influent vapor
<br /> samples were collected during the test, one after 0 25 hours of operation and one after 1 75 hours
<br /> of operation An effluent vapor sample was collected after 0 25 hours of operation Samples
<br /> ' were submitted under chain-of-custody to Sequoia Analytical (FLAP 41624) and analyzed for
<br /> TPHg by EPA method 8015, BTEX by EPA method 8020, and MTBE, ETBE, DIPE, TBA, and
<br /> TAME by EPA method $260
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