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• DISCUSSION At the time of the fourth quarter monitoring event, groundwater was encountered in the monitoring wells at depths of 22 33 and 22 50 feet below ground surface (bgs) Groundwater elevations decreased by 0 70 and 1 10 feet in the monitoring wells since the August 22, 2002, monitoring event During the first quarter 2003 monitoring event, groundwater was measured in the wells at depths of 22 81 and 22 97 feet bgs Groundwater elevations decreased 0 47 to 0 48 feet since the November 13, 2002, monitoring event Groundwater elevations measured during the fourth quarter 2002 and the first quarter 2003, are generally consistent with historical data Since March 2000, groundwater elevations appear to exhibit a generally downward trend During the fourth quarter 2002 and first quarter 2003, TPHG, BTEX, or oxygenate compounds were not detected in well MW-1, with the exception of total xylenes (0 55 pg/L) detected in the fourth quarter 2002 During the fourth quarter 2002, TPHG (110,000 µg/L), benzene (2,100 pg/L), toluene (31,000 pg/L), ethylbenzene (5,600 pg/L), and total xylenes (26,800 pg/L) were detected in well MW-2 Oxygenates were not detected in this sample These concentrations were highly anomalous relative to historical data, being approximately 2 to 3 orders of magnitude higher than anything previously reported for this well During the first quarter 2003, TPHG was reported in well MW-2 at a concentration of 61 pg/L, and BTEX and oxygenate compounds were reported as none detected, similar to historical data for the well Considering that USTs at the ICB facility were removed in 1988, and the proximity of a former ARCO Service Station, a Chevron Service Station, and a Texaco Service Station to the subject site, the existence of co-mingled plume of dissolved phase petroleum hydrocarbons beneath the intersection of Charter Way and Lincoln Street, and review of historical analytical for MW-2, it appears that the elevated concentration of TPHG and BTEX constituents detected in well MW-2 during fourth quarter 2002 are anomalous, and . may be due to several factors (i a laboratory error, sample collection or handling procedures, etc } Stratus will continue to monitor for changes in petroleum hydrocarbon concentrations at MW-2 ATTACHMENTS • Table 1 Groundwater Elevation and Analytical Data • Table 2 Groundwater Analytical Results for Oxygenates • Figure 1 Site Location Map • Figure 2 Site Map • Appendix A Field Data Sheets • Appendix B Sampling and Analysis Procedures • Appendix C Certified Analytical Reports and Chain-of-Custody Documentation 49 P II B C\Stockton\Qrt1y120031IBC Stockton-I Q03 DOC 57-KATUS