ARCHIVED REPORTS XR0000115 - Laserfiche WebLink

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1 ' Mr Ron Rowe 11/25/98 1 Groundwater Elevation Data ' Groundwater elevations measured in facility monitoring wells on October 28, 1998 (summarized in Table 1), ranged from minus (-)22 13 to—22 92 feet MSL Groundwater levels in the wells decreased approximately 2 6 feet from the ' previous monitoring event performed in May 1998 As shown in Figure 3, the groundwater flow direction is easterly at a gradient of about 2 8 x 10-3 foot per foot, which is consistent with historic trends (summarized in Table 2) ' Petroleum Hydrocarbon Analytical Data BTEX and TPH-G concentrations were only measured in samples collected from ' monitoring wells MW-1, MW-4, MW-10 and MW-12 Petroleum concentrations were not detected in samples collected from the other monitoring wells The benzene concentration in the monitoring well MW-1 sample was measured at 170 ' micrograms per liter(gg/L) The benzene concentrations in the samples collected from wells MW-4, MW-10 and MW-12 were measured at 1 1 µg/L, 10 µtg/L, and 11 µg/L, respectively ' TBA, MTBE, ETBE, and TAME concentrations were not detected in any groundwater sample during this monitoring period, nor have they ever been detected in any other monitoring period DIPE was detected in the sample collected from monitoring wells MW-12 at a concentration of 12 µg/L DIPE has occasionally been detected in samples collected from.well MW-1, which is located near the original source of the petroleum release, and from well MW-7 ' The DIPE concentration measured in the sample collected this period from well MW-12 is similar to those measured during previous monitoring events Figure 4 illustrates the approximate extent of DIPE impact in groundwater based on this monitoring event and on previous monitoring events ' Certified laboratory reports and chain-of-custody documentation are presented in Appendix C Current BTEX, TPH-G, and oxygenate analytical results are ' presented in Table 3 Historic TBA, MTBE, DIPE, ETBE, and TAME results are presented in Table 4 Historic BTEX and TPH-G analytical data are listed in Table 5 Historic tabulation and graphical presentations showing decreases in total petroleum hydrocarbons as gasoline (TPH-G) and benzene concentrations ' are presented in Table 6 and Table 7, respectively SUMMARY ' The extent of petroleum-impacted groundwater has been delineated, and appears to be contained solely within the Earthgrain's property boundary Current BTEX ' and TPH-G concentrations measured in samples collected during this monitoring event are consistent with a significant decreasing trend of petroleum impact The historic high TPH-G and benzene concentrations shown in Figure 6 demonstrate the notable decreases that these parameters have achieved The benzene ' concentration in samples collected from well MW-1, which was measured at a high of 6,800 µg/L in July 1987, is currently at 170 µg/L The TPH-G concentration in samples collected from well MW-1 have decreased from 1 1