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THIRD QUARTER,2003 GROUNDWATER MONITORING REPORT 3AMAR OIL DISTRIBUTION NOVEMBER 2003 Total xylenes were detected in the samples from all of the wells except MW-5, MW-6A, MW-6B, MW-7A and MW-713 at concentrations ranging from 28.6,ug/l in MW-3 to 19,200,ug/l in EW-1. MTBE was detected in the samples from all of the wells except MW-3, MW-6A and MW-7A at concentrations ranging from 11 pg/l in MW-5 to 180,000 µg/1 in NIW-1. Tertiary butyl alcohol (TBA) was detected in the sample collected from MW-1 at 3,600,ug/l. DIPE, ETBE, and TAME were ND in all samples taken this quarter. 1,2 DCA was detected in samples from MW-1, MW-2 MW- 4, MW-6B and EW-1 at concentrations ranging from 11 µg/1.in MW-2 to 2,900µg/1 in MW-1. The pH measurements taken this quarter during monitoring well purging were all lower than would be expected. This appears to be due to instrument malfunction. The pH meter will be checked and recalibrated prior to the next monitoring event. Water temperature stabilized during purging with maximum variation between the 2nd and 3`d well volume extraction of 0.1°C. Groundwater analytical data are summarized in Table 2 and shown on Figure 5. Copies of the laboratory reports with COC documentation are included in Appendix C. . Discussion The level of hydrocarbon constituents in the offsite wells remained relatively low except for MTBE in MW-613, which was reported at 2,600,ug/l MTBE. In both sets of cluster wells, concentrations dropped in the deeper wells for all constituents, except MTBE in MW-6B, which was essentially unchanged and TPH-G in MW-6A, which increased. As in the last quarter, the deeper wells (B), showed higher concentrations than the shallower wells(A), however the differences were smaller this quarter. Monitoring well MW-1 showed the highest results of any of the wells. EW-1 and MW-1 appear to represent the heart of the impacted groundwater plume. The other onsite wells showed similar results to those found the last three quarters, which are less than historical levels. - SCHEDULE The next quarterly monitoring event is scheduled for December 2003. The Fourth Quarter 2003 Monitoring Report will be submitted by January 31, 2003. 6