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S E C 0 R
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<br /> (GRO), BTEX, fuel oxygenates (MtBE, TAME, DIPE, EtBE, TBA), 1,2-DCA, and EDB by
<br /> EPA Method 82606.
<br /> During the first quarter 2005, each well was monitored and sampled on February 15,
<br /> 2005, except for well MW-14, which was reportedly damaged and could not be
<br /> accessed. Well MW-21, which had been discovered as paved over during the fourth
<br /> quarter 2004 monitoring and sampling event, was uncovered and accessed for
<br /> monitoring and sampling on March 24, 2005. Results are discussed below and are
<br /> summarized in TRC's Quarterly Monitoring Report, January through March 2005 dated
<br /> April 15, 2005, which is included in Attachment 1.
<br /> DISCUSSION
<br /> During the first quarter 2005, depth to groundwater ranged between 7.96 and 12.43 feet
<br /> bgs, which was in range of historical levels (approximately 5.5 feet to 13.5 feet bgs).
<br /> The direction of groundwater flow in the site vicinity was to southwest, which is also
<br /> consistent with the groundwater flow direction reported over previous quarters.
<br /> During the first quarter 2005, with the exception of a GRO concentration detected in well j
<br /> MW-3 (92 micrograms per liter [pg/L]), GRO and BTEX were not detected in the site
<br /> wells. With the exception of non-detectable concentrations of MtBE in wells MW-4, MW-
<br /> 11, MW-12, MWA 8, and MW-21, MtBE was detected in the other wells at concentrations
<br /> up to 420 pg/L. The highest concentrations of MtBE were detected in off-site wells MW-
<br /> ,r - 9 (420 pg/L), MW-10 (250 pg/L), and MW-19 (290 pg/L).
<br /> Evaluation of historical groundwater data indicates the presence of a large dissolved
<br /> plume, consisting predominantly of MtBE, extending from beneath the site to the south-
<br /> southwest. GRO and MtBE concentrations in wells MWA through MW-5, MW-8, MW-
<br /> 13, and MW-16 have decreased over time. With the exception of an increasing MtBE
<br /> concentration trend in cross-gradient well MW-9 (east of the site) and down-gradient well
<br /> MW-20 (south-southwest of the site), concentrations of GRO and MtBE have fluctuated
<br /> within historical levels in wells MW-6, MW-9 (GRO only), MWA 0, MWA 1, MW-14, MW-
<br /> 16, MW-18, MW-19, and MW-20 (GRO only). The dissolved plume is delineated to the
<br /> southwest by wells MW-15 and MW-21 and to the west by well MW-12. Three additional
<br /> wells (MW-22 through MW-24) are planned for installation during the second quarter
<br /> 2005 in an attempt to delineate dissolved impacts to the south, south-southeast, and
<br /> east-southeast of the site.
<br /> REMEDIAL PERFORMANCE SUMMARY
<br /> An OS system has been operational at the site since December 2002. A summary of
<br /> the operation of the OS system, and monthly groundwater sampling activities are
<br /> presented in the following sections. A site plan showing the layout of the OS system is s
<br /> included as Figure 1.
<br /> Ozone Injection Operation
<br /> The OS system consists of a panel mounted KVA Associates (KVA) C-SpargeTM System
<br /> that produces 4 grams per hour (0.009 pounds per hour) of ozone. Ozone is injected
<br /> I:1ConocoPhi111ps%Retai1 Sites111195XQSR&QRPS 2005/11195 QSR&QRPS 1 Q05.doc
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