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CLEARWATER G R O U P, I N C. The groundwater gradient at the subject location may be inconsistent with the local gradient for the following reasons: • The gradient (calculated on the basis of the existing'three monitoring wells) is I flat; the difference in groundwater elevations is only 0.04 to 0.06 foot - i The three wells are in close proximity to one another (the maximum distance between any two wells is approximately 75 feet) . i The spatial arrangement of the wells 15 not the optimum geometry for calculation of the data, given only three data points and the relatively flat gradient. II 4.2 .Groundwater Sample Analytical Results TPHg, TPHd, and BTEX were not detected -Ln concentrations exceeding method detection limits in any of the three groundwater samples (Table 1). Concentrations of TPHd ranged from 100 to 530 ppb in samples collected during the two previous sampling events. ' - On November 13, AEN- was requested to r -evaluate the results of the TPHd ; _ analyses in all three samples. Laboratory personnel re-integrated the chromatographs, and the original analytical results indicating nondetectable TPHd were confirmed. Analytical results are 'disp ayed graphically on Figure 4; and laboratory reports and chain-of-custody forms a e attached as Appendix B. 5.0 RECOMMENDATIONS Petroleum hydrocarbons were not detected i i any sample collected during this j monitoring event. Historically, gasoline consti ents have not been detected in any of the samples analyzed, although samples f om all three wells have contained TPHd. Clearwater recommends that these sults be confirmed by resampling groundwater for at least two more quarters. On October 4, 1995 Clearwater submitted the Workplan for Additional Site Assessment to Mr. Ron Rowe of the PHS/EI-11). The Workplan proposes drilling one soil boring in the former fuel dispenser location and installing four monitoring D-144 3Q95 3 November 28,1995 I t I