ARCHIVED REPORTS_XR0009613 - Laserfiche WebLink

Home Browse Search

I Quarterly Monitoring Report October 2000 Canepa's Car Wash(Park Street) tanuary 1$,2001 Page 5 Iconcentrations of BTEX detected in the groundwater sample collected from MW-5 indicate a decrease in coiiL,entration of these constituents in samples collected from this well since July None of the analytes of I concern were detected in the groundwater sample collected from monitor wells MW-7 TPH-G was detected in the groundwater samples from MW-1 TPH-G and all BTEX constituents were detected in the groundwater samples collected from MW-2 and MW-5 Toluene, ethyl benzene, total xylenes, MTBE, and TPH-G were detected in the sample from MW-6 Concentrations of TPH-G and MTBE were detected in the groundwater sample collected from MW-3 A concentration of MTBE was detected in the groundwater sample collected from MW-4 The fourth quarter, 2000, laboratory analytical results 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 I5 2.1 DISCUSSION OF BENZENE CONCENTRATIONS The concentration of benzene has decreased over time in monitor well MW-2 (Figure 6, Appendix A) It I appears that as the groundwater elevation has risen, the concentration of benzene in MW-2 has decreased possibly as a result of lower concentrations being naturally bioremediated with available dissolved oxygen levels Benzene concentrations in MW-5 have increased and decreased as the groundwater I elevation has increased or decreased It is important to note that both wells are drowned, with 16 to 21 feet of water above the well screen, and thus we are not seeing the first groundwater with possibly higher concentrations I5.2.2 DISCUSSION OF MTBE CONCENTRATIONS I 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-3 and MW-4 5.2.3 DISCUSSION OF OTHER ANALYTE CONCENTRATIONS I Concentrations of toluene, ethyl benzene, total xylenes, and TPH-G have decreased over time in monitor well MW-2, but all have increased in monitor well MW-5 (Table A, Appendix B) In general, concentrations of analytes have decreased as the groundwater elevation has increased, except in MW-5, I which has seen an increase in contamination It is important to note thatsince all of the monitoring wells are drowned, we are probably not sampling the shallowest water with the highest concentration of contamination Since we are not sampling these high concentrations, the actual concentrations of the I plumes have not been measured and are not known According to Figures 3 and 4, the plumes probably extend beyond the site, therefore the current monitoring wells cannot measure the northern extent of the contaminant plumes i I I It,� CONDOR