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25 March 2002 AGE-NC Project No. 95-0106 Page 3 of 4 4.2. ANALYTICAL RESULTS OF GROUND WATER SAMPLES Petroleum hydrocarbons were detected in the ground water samples collected from monitoring.well MW-4, located north,of the site in the generally down-gradient direction; TPH-g,benzene, toluene, r ethylbenzene and total xylenes were detected at concentrations of 4,200 micrograms per liter 83 4g/l, 12, µg/l, 180,pg/l and 56 gg/l;respectively. No additional hydrocarbon-compounds were ' detected in the samples analyzed; MW-1 was not sampled_ this quarter. Analytical results of groundwater,samples are summarized on Table 2. The laboratory report(MAI ' Lab ID 91028 through 91034), QA/QC and chain-of-custody are included in-Appendix B. x ' 5.0. SUMMARY AND CONCLUSIONS The following conclusions were drawn from the results of the site investigation: , • The groundwater was generally northward on 20 February 2002, and gradients were - calculated to range from 0.006 toward.the north-northwest to 0.007 toward the north- northeast: • Dissolved petroleum hydrocarbons were detected in ground water sainples from monitoring well MW-4,located down-gradient off-site from the former UST excavation;MW-1 was not ; sampled this quarter.' • BTEX compoundsw ere detected in the water sample collected from MW-4. The concentration :of benzene in the sample exceeded the State, of California maximum contaminant level(MCL) of.l µg/l for drinking water. Analytical'data,from monitoring wells MW-2-and.MW-7 limits the horizontal extent of dissolved-hydrocarbons.south and east of the'site, respectively. Analytical,data from wells MW-3 and MW-6 limits the extent of dissolved hydrocarbons northeastward of'the site. ' Analytical data from monitoring well MW-5 limits the extent of dissolved,hydrocarbons north-westward"of the,'site. The extent of-dissolved hydrocarbons"'to• the west is not ' completely'defined at;this time. '; •: Continued detection of TPH-g and BTEX in ground water samples collected from the off-site well MW4 indicates that the plume of impacted ground water has migrated off-site towards ' the north, however, the general lack of detection,of hydrocarbons in the MW-7, MW-6, MW-,5 and MW-3 wells shows that the plume is not wide-spread and has not migrated northeast of MW-4 or northwest of,the former UST,pit. Advanced GeoEnvironmental,Inc.