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Page 3 <br /> Mr Michael Infurna Jr,Senior REHS <br /> October I t,2002 <br /> EHD requested that additional investigation be performed to assess the extent of <br /> petroleum impact PSC submitted a September 24, 2001 Subsurface Site <br /> Investigation Workplan to EHD, which proposed further assessment EHD <br /> approved this work plan in a letter dated October 16, 2001 <br /> PSCerformed the latest investigation in March of 2002 PSC drove 6 Geoprobe <br /> p g <br /> borings (PH-3 through PH-8), installed one groundwater monitoring well <br /> (MW-4), constructed one air sparging well (SP-1), one soil vapor extraction well <br /> (VW-1), and collected soil and groundwater samples for laboratory analysis <br /> Investigation findings, submitted to EHD in the May 14, 2002 March 2002 <br /> Subsurface Site Investigation report, included the following <br /> • Subsurface soils in the vicinity of the Site are primarily comprised of silt and <br /> clay to at least 50 feet <br />■ • Initial groundwater, situated in the clayey matrix, was typically observed at a <br /> depth of 30 to 35 feet Groundwater is slow to yield, but typically rises under <br /> confined pressure to about 23 to 25 feet <br /> • Groundwater flows easterlt at a gradient of about 0 0026 ft/ft <br /> • BTEX concentrations in soil samples collected above the groundwater table <br /> are relatively low compared to those obtained below Higher BTEX <br /> concentrations in soil samples collected below the groundwater table may be a <br /> result of the contaminated groundwater present within their matrix <br /> • TPHg concentrations in soil samples collected above the groundwater table <br /> are relatively higher compared to those obtained below BTEX concentrations, <br /> once potentially present in these higher TPHg-impacted soil samples, appear <br /> to have degraded <br /> j • The lateral extent of petroleum impacted soil appears to be narrowly confined <br /> in the vicinity of the former UST The vertical extent of impact is evaluated to <br /> be 50 to 55 feet <br /> • Oxygenate compounds have not been detected in any soil sample <br /> • BTEX and TPHg concentrations in groundwater at the MW-2 location are <br /> relatively high <br /> • BTEX and TPHg concentrations in groundwater at the MW-1, MW-3, MW-4 <br /> and PH-8 locations are relatively low or were not detected <br /> • BTEX and TPHg concentrations in groundwater at the PH-6 and PH-7 <br /> locations may be a result of previous retail gasoline operations at the 1725 El <br /> Dorado Street property <br />