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Quartet ly Monitoring Report 0(,tnher 2000 Canepa's Car Wash (Pat k Street) lie January 25 2001 Page 5 groundwater sample fiom MW-1 was further analyzed and low concentrations ofcls-l,2-dichloroethene, trichloroethene, and tetrachloroethene wete piesent TPH-G and BTEX weie detected in the groundwater ' samples collected fionn MW-2 and MW-5 Low concentrations of benzene, ethyl benzene, TPH-G and MTBE were detected in the groundwater sample collected troin MW-3 Low concentration of MTBE were detected in the groundwater samples collected from MW-1, MW-4, and MW-6 The first quarter, ' 2001, laboratory analytical results geneially indicate that the area of groundwater contamination most impacted by petroleum hydrocarbons is in the northern portion of the site in the vicinity of monitor wells MW-2 and MW-5 ' 5 2 1 DISCUSSION OF BENZENE CONCENTRATIONS The concentration of benzene has decreased with time in monitor well MW-2 (Figure 6, Appendix A) As the groundwater elevation has increased, the concentration of benzene in MW-2 has decreased Benzene concentrations in MW-5 have generally increased as the groundwater elevation has increased It is important to note that both wells are drowned, with 16 to 21 feet of water above the well screen Therefore the first gioundwatet, with potential greater BTEX concentrations, is not being sampled 5 2 2 DISCUSSION OF MTBE CONCENTRATIONS ' Concentrations of MTBE in monitor well MW-6 have decreased slightly over time, with a recent increase in October 2000 (Figure 7, Appendix A) There has also been a reappearance of low • concentrations of MTBE in monitoring wells MW-1, MW-3, and MW-4 5.2 3 DISCUSSION OF OTHER ANALYTE CONCENTRATIONS ' Concentrations of toluene, ethyl benzene, total xylenes, and TPH-G have decreased over time in monitor well MW-2, but all have increased in rnonitor well MW-5 (Table A, Appendix B) In general, concentrations of analytes have decreased as the groundwater elevation has increased, except in MW-5, ' which has seen an increase in contamination It is important to note that since all of the monitoring wells are drowned, the shallowest water with the potentially highest contaminant concentrations is not being sampled Therefore, the actual concentrations of the plumes have not been measured and are not known ' Accoiding to r1gures 3 and 4, the plumes probably extend beyond the site, therefore the current monitorin i wells cannot ineasuie the northei n extent of the contdininant plumes I • �M CONDOR