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r • 3.0 RESULTS 3.1 Depth to Groundwater and Groundwater Flow Direction The depth to groundwater on April 5 was approximately 27 feet below grade (Table l) This depth is approximately 2 5 feet greater than a year ago, but about 2 feet less than in December 2003 Using the 3-point method to contour these values yields a groundwater elevation (piezometric surface) map with a uniform gradient of 0 0027 ft/ft sloping to the southwest (Figure 3) This is the first time since the wells were installed that flow was in this direction Usually the flow direction is southeast, although 1n January 2003 it was to the northeast 3.2 Laboratory Results Hydrocarbon concentrations in JLM-4 continue to be below the detection limit except for MTBE (26 parts per billion--ppb) and TBA (I 1 ppb) This is the first time that TBA has been detected to this well and the second consecutive quarter to which MTBE has been detected (at twice the concentration of the previous quarter) This suggests that gasoline oxygenates have migrated to this well since the third quarter of 2003 Oxygenate and lead scavenger concentrations in JLM-3 and JLM-5 remained constant this quarter, but Total Petroleum Hydrocarbon and BTEX concentrations rose in both wells This is probably due to differences in laboratory procedures or interpretation of the • data acquired using EPA method 8015 Samples collected in the fourth quarter of 2003 were analyzed by Excelchem Analytical Laboratory gather than by McCampbelI Analytical Because there is less variability in the analysis of data using EPA method 8260, the oxygenate and lead scavenger data from the two laboratories are more consistent Which laboratory's EPA 8015 data are more accurate is unknown perhaps 1t would be advisable in the next sampling event to have both laboratories analyze the samples using both methods, or submit duplicate samples to three laboratories to compare the EPA 8015 results and determine which laboratory should be used in the future � I 4.0 CONCLUSIONS AND RECOMMENDATIONS In the Fourth Ouarter 2003 Monitoring Report we observed that concentrations have declined in both JLM-3 and JLM-5 over time and remained at or below detection Iimits in JLM-4, suggesting that natural attenuation may lead to site cleanup without the necessity for active remediation The declining pattern pertains only to TPH-g and BTEX, gasoline oxygenate and lead scavenger concentrations have remained largely unchanged throughout the past two years except for the recent rise in JLM-4 (Table 2) Whether the apparent decline in non-oxygenate concentrations is real is now somewhat uncertain, because concentrations reported in April 2004 rose above those reported in late 2003 Hence, continued monitoring is necessary to establish a clear pattern in the concentrations of all analytes Due to the uncertainty regarding the concentrations . reported by different laboratories using EPA method 8015,we recommend one of the following three protocols 1) collect duplicate samples and instruct both Exclechem and 3