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- WINZLERQSz_KELLY , 0 N 5 V L T I N G E N G I N E E R G Mr A K Jain March 4, 2005 Page 2 Chemical Analysis• Analytical Sciences Laboratory (Analytical Sciences) of Petaluma, California (a California-certified laboratory) analyzed groundwater ' samples for total petroleum hydrocarbons as gasoline (TPH-G) by EPA Method 8015M, and for benzene, toluene, ethyl benzene, and total xylenes (BTEX), oxygenated fuel additives, and lead scavengers ' by EPA Method 8260B ' GROUNDWATER MONITORING AND SAMPLING RESULTS The groundwater elevation data and flow direction are presented in Tables 1 and 2 A groundwater contour map (Figure 3) illustrates the groundwater elevation contours and flow direction at the site on January 13, 2005 As Figure 3 shows, the groundwater flow direction at the site was toward the northeast, at an approximate gradient of 0 01 ft/ft ' During purging activities, the parameters of pH, conductivity, temperature, and oxidation-reduction potential (ORP) were monitored in the groundwater extracted from the wells A summary of these ' indicator parameters is provided in Table 3 Table 4 summarizes the analytical results of groundwater samples collected from monitoring wells at the site Figure 4 depicts the concentrations of TPH-G, benzene, and methyl tert-butyl ether (MTBE) in the groundwater samples collected on January I3, 2005 The groundwater samples collected from MWA, MW-3, and MW-4 did not quantify any petroleum-related constituents above ' the laboratory's reportable detection limits MTBE was the only petroleum-related constituent quantified at diminutive concentrations in the groundwater samples collected from monitoring well MW-2 The Iaboratory noted the detection of tetratchlorethene (PCE) in monitoring well MW-4 at a ' concentration of 1 3 4g/L However, the State of California primary drinking water maximum contaminant level (MCL) for PCE is 5 gg/L The laboratory QA/QC included the use of method blanks to exclude false-positive analyses and the use of laboratory control samples to evaluate the percentage recovery of known analyte spikes The recovery percentages for all of the sample analytes were within acceptable ranges The complete laboratory report, QA/QC data, and the chain-of-custody form for the groundwater samples are included in Appendix B RECOMMENDATIONS The January 13, 2005 sampling event venfied that the concentrations of petroleum hydrocarbons (MTBE only) in the groundwater at the site are very low and well below MCLS Moreover, the deep well (MW-4) consistently did not contain any petroleum-related constituents, indicating that the lower aquifer is not impacted by the former fuel tank Winzler & Kelly's contract to provide