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,s Mr Kyle Christie
<br /> �r
<br /> December 11, 1995
<br /> Page 2
<br /> All groundwater samples were analyzed for benzene, toluene, ethylbenzene, and xylenes
<br /> (BTEX) and total petroleum hydrocarbons as gasoline (TPH-G) by U S Environmental
<br /> Protection Agency (EPA) Method 503018020, and 8015 Modified Additionally, a
<br /> groundwater sample from well MW-3 was analyzed for fecal coliform Well MW-3 is within
<br /> 50 feet of a sewer line Fecal coliform analysis is required by San Joaquin County for any
<br /> wells within 50 feet of a sewer line
<br /> Results and Discussion
<br /> Figure 1 presents the groundwater elevations for each well The groundwater elevations were
<br /> highly variable across the site this quarter because of the influence of the remediation system
<br /> and could not be logically contoured Summaries of depth-to-water measurements and
<br /> calculated groundwater elevations are presented in Table 1 Water-level elevations in Table 1
<br /> are corrected for the presence of free product Since groundwater monitoring began in 1989,
<br /> the general groundwater flow direction has been to the northeast at this site, under hydraulic
<br /> gradients ranging from 0 001 to 0 005 Table 2 lists historical groundwater flow directions
<br /> and hydraulic gradients for this site
<br /> Depth-to-water on September 11, 1995 ranged from 13 21 feet below the top of the well
<br /> casing (TOC} in well BHD-1, to 15 96 feet below TOC in well E-11 Well E-10 contained
<br /> • approximately 1 31 feet of free product on September 11, 1995 Since the last quarterly
<br /> monitoring event (June 1, 1995), water-level elevations in all monitoring wells have
<br /> decreased an average of 194 feet
<br /> Benzene was not detected in wells E-5, E-7, E-12, PR-1, PR-2, BHD-2, MW-3, and MW-4,
<br /> but was detected in wells E-2, E-3, E-4, E-6, E-8, E-9, E-11, BHD-1, MW-1, MW-2, and
<br /> MW-5 at concentrations ranging from 7 4 micrograms per liter (pg/L) in well E-8, to
<br /> 1900 pg/L in well E-3 With the exception of wells E-5, E-6, E-9, and MW-1, these results
<br /> are consistent with previously reported results This quarter is the first time that benzene has
<br /> not been detected in well E-5 since sampling began in 1988 The benzene concentration
<br /> identified in well E-6 is the lowest it has been since sampling began in 1988 The
<br /> concentration of benzene in well E-9 is the highest it has been since sampling first began in
<br /> August 1988 Benzene was detected for the first time in well MW-1 since monitoring began
<br /> in November of 1993
<br /> TPH-G was not detected in wells E-12, PR-1, PR-2, BHD-2, MW-3, and MW-4, but was
<br /> detected in wells E-2, E-3, E-4, E-5, E-6, E-7, E-8, E-9, E-11, BHD-1, MW-1, MW-2, and
<br /> MW-5 at concentrations ranging from 75 pg/l in well E-7 to 150,000 µg11 in well E-9 These
<br /> results are consistent with previous results with the exception of wells E-5, E-6, E-9, MW-1
<br /> and MW-2 The TPH-G concentration is higher than previously reported values in well E-9
<br /> and MW-2, and is lower than previously reported values in wells E-5 and E-6 This quarter
<br /> is the first time that TPH-G was detected in well MW-1 since monitoring began in November
<br /> • of 1993 Analytical results of groundwater samples are summarized in Table 3 The
<br /> Use or disclosure of data continued on this sheet is subject to the restriction specified at the beginning of this
<br /> document
<br /> 20W,RFPOPTWRD95QTR DOC
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