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Chemical analysis . The groundwater samples collected were analyzed for Total Petroleum Hydrocarbons as Gasoline (TPHG) ; Benzene, Toluene, Ethylbenzene and Xylene (BTEX) and Methyl-tert-butyl ether (MTBE) . The groundwater samples were analyzed for TPHG by EPA Method 8015 modified with purge and trap preparation 5030 (GC/FID) with detection limits of 50ug/l. EPA Method 602 was utilized for BTEX with a detection limit of 0. 5ug/l as required by the SJCEHD. The results of the analysis of the groundwater samples in parts per billion (ppb) are shown in Table 3 . The laboratory data sheets with detection limits and COC documentation are contained in Appendix B. TABLE 3 March 11, 1996 Groundwater Sample Analysis Results in ppb. Sample TPHG MTBE B T E X MW-1 320 ND 1. 1 1.4 1. 4 3 .7 MW-2 3 , 600 30 66 6. 5 100 17 MW 33 6, 500 64 2 , 000 35 110 30 ND = Not Detected The concentrations of TPHG and BTEX in the groundwater are high. Quarterly sampling should be continued. SUMMARY, CONCLUSIONS AND RECOMMENDATIONS The groundwater samples from the three wells had actionable levels of TPHG and Benzene. The calculated gradient is to the southeast at approximately 0. 002 ft/ft. The gradient has shifted from a southwesterly to a southeasterly direction with a slight slope. The local groundwater recharge conditions irrigation and slough depths are most likely the main influences on the gradient. The levels of TPHG and BTEX in groundwater are similar to the values reported in the prior quarterly environmental investigation at this site. Continued quarterly monitoring readings obtained over a longer period of time should indicate a consistent gradient or provide a reason for the gradient variability. We propose continued quarterly sampling and gradient data measurements. 6