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Page 3 Mr Michael Inform Jr,Senior REHS IP August 21,2000 petroleum product, and then purged a minimum of three well volumes from each well with clean, disposable bailers Free phase petroleum product was not observed in any of the wells Temperature, pH, and electrical conductivity ' parameters were also measured during the purging process to assess groundwater stability. Purged groundwater was placed in 55-gallon drums,which were subsequently removed from the site and properly disposed of Groundwater samples were collected from each well with its own dedicated ' bailer The samples were placed in clean, laboratory-provided glass containers, sealed, labeled, and stored in an insulated iced chest The samples were delivered to Acculabs, Inc laboratory in Davis, California, accompanied by chain-of- custody documentation, for chemical analysis Samples were analyzed for BTEX and TPHg compounds using EPA Method 602/8015 Samples were also analyzed for the oxygenate compounds tert-butanol (TBA), methyl-tert-butyl ether (MTBE), di-isopropy ether(DIPE), ethyl-tert-butyl ether(ETBE), and tert- amylmethyl ether(TAME) using EPA Method 8260B Groundwater Level Measurements As shown in Table 1 (Attachment 2), groundwater within the monitoring wells ' were measured by Philip at depths similar to those measured by GZA Groundwater depths ranged from 22 78 feet (below the top of the well casing) to 23 11 feet The corresponding groundwater elevations, evaluated during this ' monitoring period, ranged from minus (-)1169 feet to--11 83 feet relative to mean sea level As shown in Figure 3, groundwater flows southeasterly at an approximate gradient of 1 75 x 10"3 feet per foot Groundwater Sample Analytical Results ' While BTEX and TPHg concentrations in the current MW-2 groundwater sample remain relatively high,these concentrations are somewhat lower than those collected by GZA in July 1999 As shown in Table 2, benzene concentrations decreased from 20,000 micrograms per liter(ug/1) in the July 19, 1999 sample to 15,000 ug/1 in the June 29, 2000 sample TPHg similarly decreased from 120,000 ug/1 to 70,000 ug/l Benzene and TPHg groundwater sample results are illustrated in Figure 4 and Figure 5,respectively Acculabs reports are contained in ' Attachment 3 Unique to this recent monitoring event is the detection of petroleum hydrocarbons collected in the upgradient monitoring wells MW-1 and MW-3 Groundwater