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Laboratory results and Cham-of-Custody Forms for the period from January 1994 to February 1995 are included in Appendix D These ' analytical results are summarized below Former Tank SxtC #1r The chemical analysis results of ground water ' samples collected from the five monitoring wells located at Former Tank Site #1 are summarized in Table 4-3 Of the five monitoring wells, only wells MW-4 and MW-5 commonly exhibited detections of ' TPH and/or BTEX compounds during the monitoring period Hydrographs illustrating changes in benzene and TPH concentrations in ground water samples collected from monitoring wells MW-4 and ' MW-5 are shown on Figures 4-5 and 4-6, respectively TPH detections in samples collected from both wells decreased significantly over the monitoring period Samples collected from MW-4 exhibited their highest detections during the first sampling event (April 1991, 2 10 mg/1) and have intermittently exhibited non- detectable levels since 1992, TPH was not detected in any samples collected in the last three sampling events from this well Likewise, TPH concentrations in samples collected from well MW-5 have decreased significantly since inception of monitoring The highest TPH detection (20 mg/1) was detected during the first sampling event, samples collected during the last three sampling events exhibited TPH concentrations less than 1 mg/l ' Similarly, BTEX detections decreased significantly over time in samples collected from these two wells Benzene is the only BTEX compound that exceeded state Maximum Contaminant Levels (MCLS) in samples ' collected from MW-4 These benzene detections ranged from 0 0013 mg/l in the first sampling event to nondetect in the last three sampling events With the exception of one sample collected in May 1994, no ' BTEX compounds have been detected in samples collected from MW-4 since June 1992 All of the BTEX compounds exceeded the state MCLs at least once in samples collected from MW-5 during the monitoring ' period, however, toluene, ethylbenzene and xylene exceedances occurred only in the early phases of monitoring, and no exceedances were noted in MW-5 samples after March 1993 Benzene concentrations in MW-5 samples ranged from a maximum of 2 9 mg/l (March 1992) to 0 12 mg/1 (November 1994) and increased slightly during the last monitoring event to 0 21 mg/l Ethylene dibromide and organic lead were not detected in any ground water samples collected from Former Tank Site #1 Total lead detections were less than 0 04 mg/l in all samples collected from the site ' 4-7