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January 1988, Anderson Consulting Group (ACG) installed wells MW-4 and <br /> MW-5 ACG subsequently drilled soil borings 90-1 and 90-2, and installed <br /> wells MW-6 and MW-7 in February 1990, then MW-8 in September 1990 <br /> Philip (formerly Burlington Environmental) installed wells MW-9 through <br /> MW-13 in March 1994, and piezometers PZ-1 and PZ-2 and air sparge well <br /> SP-1 in September 1994 <br /> I <br /> Philip performed a soil venting and air sparging pilot test in October and <br /> November of 1994 to evaluate the effectiveness of this remediation <br /> technology Soil venting tests were performed using well MW-1, and air <br /> sparging tests were performed using well SP-I Results of the tests, contained <br /> in Philip's February 1, 1995 Final Remediation Plan, indicated that soil <br /> venting and air sparging would be effective in remediating hydrocarbon <br /> impact <br /> In June 1995, Philip proceeded with the installation of air sparging wells SP-2 <br /> through SP-6 However, implementation of the sparge and vent remediation <br /> was postponed due to petroleum hydrocarbon concentration reductions that <br /> were observed to be naturally occurring at the site <br /> In May 1999, Philip performed the latest subsurface investigation using cone <br /> penetrometer (CPT) technology Three CPT borings (CPT-1 through CPT-3) <br /> were driven, and soil and groundwater samples were collected for analysis <br /> This CPT investigation indicated that the lateral extent of impacted <br /> groundwater is largely contained within Earthgrain's property boundaries <br /> Results from this investigation were reported in Philip's May 1999 Subsurface <br /> Investigation and Groundwater Monitoring Report <br /> 13 Historic Groundwater Conditions <br /> Assessment of petroleum hydrocarbon impact in groundwater has been <br /> performed at this site since July 1987 Historic groundwater monitoring <br /> indicates that decreases of petroleum hydrocarbon concentrations have <br /> occurred due to natural degradation Benzene concentrations in samples <br /> collected from well MW-1, located near the original source of the petroleum <br /> release, have decreased from a high of 6,800 micrograms per liter (µg/L) in <br /> July 1987 to a low of 170 µg/l, in October 1998 (see Table 4) Total <br /> petroleum hydrocarbons as gasoline (TPH-G) concentrations in samples from <br /> MW-I have decreased from a high of 196,000 µg/L in April 1993 to a low of <br /> 15,000 µg/l, measured during this August 1999 monitoring event (see Table 3 <br /> and Table 4) <br /> Oxygenate compounds methyl tert butyl ether (MTBE), ethyl tert butyl ether <br /> (ETRE), tert butyl alcohol (TBA), and tert amyl methyl ether (TAME) have <br /> never been detected in site groundwater samples (see Table 5) The oxygenate <br /> compound di-isopropyl ether(DIPE) has been measured at concentrations less <br /> s <br /> August 1999 Groundwater Monitoring Report Prepared for THE CARTHGRAINS COMPANY Prepared by Philip Services Corp <br /> P I62400132 121382£G\6240014510899MON DOC October 9, 1999 <br />