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' • � KLEINFELDER well boring soil samples were below applicable regulatory levels and appear to be consistent with background levels. ' Kleinfelder recommends removal of the stockpiled soil from the three excavations to an appropriate landfill and according to the current laws and regulations ' 6.2 GROUNDWATER SAMPLING DISCUSSION Groundwater flow direction at the site is estimated towards the northeast at a gradient of ' approximately 0.0028 ft./ft. based upon soundings on July 6 and July 11, 2001. Depth to water was measured at depths of about 9 to 10 feet bgs. See Table 5 and Plates 3 and 4 for tabular and ' graphical representations of the elevation data and groundwater contours. Pumping influences and seasonal groundwater fluctuation may also affect groundwater flow and gradients. ' Four (4) groundwater samples were collected around the perimeter of LE-C and analyzed for petroleum constituents including TPH-G, BTEX, Oil & Grease, 5 LUFT Metals, and 5 Oxygenates (See Section 5.2 for details). The results of these soil samples are summarized on ' Table 4 in the Appendix. Three of five metals (Cr, Ni and Zn) and the analyte xylenes were detected from one or more of ' the four groundwater samples submitted for analyses. The concentrations of dissolved metals detected in the four groundwater samples were found to be below State and Federal MCLS. Total xylenes were detected in a single groundwater sample collected from temporary well TW-1. TW-lis located southeast and cross-gradient of LE-C and downgradient of the former tank farm of the previous owner R&B Trucking Company. Based on this observation it does not appear that this constituent in groundwater is related to contaminants from LE-C, but may be the residual ' affect of the former R&B tank farm. Xylenes were detected from the TW-1 groundwater sample at a concentration of 0.75 µg /1, which is below the State and Federal Primary Maximum ' Contaminant Levels (MCLS) for xylenes of 1,750 and 10,000 µg/1, respectively and is representative of naturally occurring background levels. Temporary well TW-2 was installed downgradient of SE-B. Based on this observation and that a groundwater sample collected from this well was none detected for the requested analyses (see Section 5.2), it does not appear that the contaminants associated with SE-B have impacted ' groundwater. ' 6.3 POTENTIAL SOURCES OF CONTAMINATION At this time the source of contamination from location SE-B and LE-C is unknown. The R&B ' maintenance shop, AST, USTs and secondary containment structures were generally located on the western portion of the site and operations have existed since approximately the late 1960's to 1990's. The maintenance shop in particular was formerly located over LE-C and in proximity to 204341-11.E01/2011R959 Page 28 of 31 Copyright 2001,Kleinfelder,Inc. August 21,2001