ARCHIVED REPORTS_PHASE II ENVIRONMENTAL SITE ASSESSMENT

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W1C]rR • Southwest, Inc. however, this detection may be indicative of an onsite source of TPH-g, which would be consistent with historical site usage. SWPPP maps show motor blocks have historically been stored near the location of B-2 (Hugo Neu& Sons, 1992 and The Learner Company, 1997). The three monitoring wells installed on the Learner site in 2002 following removal of the UST were located in the vicinities of B-8,B-11 and B-12. The wells were monitored quarterly during 2003, and during this time TPH-d was detected in all of the wells during all four quarters (Clayton Group Services, 2004). The highest TPH-d levels were consistently found in the well located near B-8, west of the hazardous materials container storage area. During this Phase II ESA, the highest dissolved TPH-d concentration was detected in the groundwater sample from B-8. Documented TPH-d contamination to groundwater remained when monitoring of the site was discontinued and the UST case was closed by the agencies in 2004. Detectable soil concentrations of TPH-d and TPH-g were also documented to have been left in place and may be contributing to soil and/or groundwater concentrations detected during this Phase II ESA. Widespread concentrations of TPH-d and TPH-mo in groundwater beneath the site may also be indicative of the long history of the site which has included auto shredding, onsite fueling, • vehicle and equipment maintenance and storage of a variety of petroleum products, as identified in the SPPCP. Learner has also stored and processed an extensive variety of metal products, including engine blocks from diesel trucks. The TPH-d and TPH-mo chromatograms typically show no recognizable pattern which is consistent with multiple sources and ages of petroleum hydrocarbons. The concentrations of TPH-d and TPH-mo in groundwater samples correlate somewhat with TPH-d and TPH-mo concentrations in one-foot soil samples (see Figure 4). Variations may be attributable to an array of factors including apparent multiple ages and sources of TPH releases, preferential pathways through coarser-grained subsurface soils and fluctuations in groundwater flow direction over time. It is not possible to compare the CAM17 metal analyses of groundwater samples from B-1 through B-7 with B-8 through B-18, since the former samples were not filtered and contained sediments. They provide a measurement of the total concentration of metals in the water samples, including dissolved and particulate metals. The latter samples were filtered and thus reflect only the dissolved metal components. Comparison of the dissolved metal concentrations from B-8 through B-18 to MCLS shows them all to be below MCL standards. • 704. PRI.05 27 July 21, 2008