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4 <br /> `11r <br /> • <br /> No floating product or sheen was observed in well MW 1 Groundwater monitoring data since <br /> December 1990 are summarized in Table 1 <br /> A potentiometric surface map for the July 29, 1996 monitoring event is presented on Figure 2 <br /> Groundwater beneath the site generally flows to the south with components to the southeast at <br /> an average gradient of 0 0045 feet per feet (approximately 23 8 feet per mile). Historically, <br /> groundwater elevation data has suggested an irregular groundwater surface beneath the site, <br /> possibly due to the heterogeneous nature of the soils and/or the varying well depths While <br /> attempting to sample well MWSR, it was discovered that the well was partially filled with <br /> concrete from site paving activities Water level data from MWSR was not used in calculating <br /> the gradient direction or magnitude <br /> On July 29, 1996, groundwater samples were collected from wells MW1R, MW2, MW3, <br /> MW4 and MW6, after purging at least three casing volumes of water No sample was <br /> collected from well MWSR due to the presence of concrete in the casing The well was <br /> destroyed and replaced with well MW5R2 On August 29, 1996, a groundwater sample was <br /> collected from well MW5R2 <br /> Monitoring wells were purged and sampled in accordance with the field methods included in <br />• Attachment 1. Well purge logs are included as Attachment 2 <br /> LABORATORY ANALYSIS <br /> Groundwater samples were transported under chain of custody protocol to Sequoia Analytical <br /> Laboratory in Redwood City, California (ELAP #1210) for analysis of benzene, toluene, <br /> ethylbenzene, and xylenes (BTEX), and methyl tertiary-butyl ether (MTBE) utilizing EPA <br /> method 8020, total petroleum hydrocarbons as gasoline (TPHg) and as diesel (TPHd) utilizing <br /> EPA method 8015 modified, and halogenated volatile organics (HVOCs) utilizing EPA <br /> method 8010 <br /> Petroleum hydrocarbons were detected in the samples collected from wells MW1R, MW2 and <br /> MW3 An unidentified hydrocarbon in the TPHd range was detected at concentrations ranging <br /> from 140 parts per billion (ppb) to 370 ppb in wells MW2 and MW3 TPHg was detected in <br /> the sample from monitoring well MW 1R at a concentration of 4,000 ppb MTBE was not <br /> detected in any of the samples Analytical results of petroleum hydrocarbon constituents are <br /> summarized in Table 2 Laboratory data sheets and chain-of-custody documentation are <br /> included in Attachment 3 <br />• <br /> 1500771QUARTLYL3QR-1996 doc Z <br /> • <br />