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' 14 June 2001 • AGE-NC Project No 98-0505 ' Page 4 of 5 ' Laboratory results of water samples analyzed for petroleum hydrocarbons are summarized in Tables 2, 3 and 4 The laboratory reports for the quarterly monitoring event (MAI Lab Nos 67663 through 67670) QA/QC reports and chain-of-custody form are included in Appendix C Concentrations of TPH-g and benzene in ground water are iIIustrated on Figures 4 and 5 ' 4.0. SUMMARY AND CONCLUSIONS ' The findings of the 15 and 16 May 2001 site investigation events include the following • Contamination by TPH-g was encountered in ground water samples collected from seven of ' the eight on site monitoring wells at the site(MW-1,MW-2,MW-3,MW-4,MW-6,MW-7 and MW-8) Concentrations as high as 100,000 µg/l were detected • BTEX constituents were detected in five of the eight ground water monitoring wells with concentrations as high as 7,900 µg/l benzene, 22,000 µg/1 toluene, 2,500 µg/1 ethylbenzene and 11,000 4g/1 total xylenes lie DIPE was detected in MW-8 at a concentration of 1 2 µg/1 and TBA was detected in MW-7 at a concentration of 22 µg/1 Fuel oxygenates had not been detected prior to the May 2001 monitoring event MTBE, ETBE and TAME were not detected in any of the ground water samples collected • 1,2-DCA was detected in ground water samples collected from seven of the eight monitoring I wells at the site at concentrations as high as 410 µg/l (MW-1) EDB was not detected in any of the ground water samples collected during the May monitoring event • The horizontal and vertical extent of contamination related to the former UST has not yet been defined in soil or ground water Measured ground water elevation is approximately 11 4 feet below msl, and was within the screened interval of the two shallow monitoring wells (MW-7 and MW-8) Ground water was approximately 10 feet above the screened intervals of MW-1 through MW-5 and was approximately 40 feet above the screened interval of the deep well MW-6 I5.0 RECOMMENDATIONS Based on the results of this and previous investigations, AGE recommends • Continued quarterly monitoring of the ground water monitoring network • Advanced GeoEnv►ronmental,Inc