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ME <br /> Offl EVA <br /> Coca-Cola EnterprisQ,, - West <br /> Job No. 9GO54 <br /> Soil gas surveys consist of the sampling and analysis of the soil gases that reside in the <br /> pore space of the wtsaturated zone above the water table. Since many of the common <br /> organic compound:, and industrial solvents exhibit significant .;vapor pressures and are <br /> relatively insoluble in water, their introduction into subsurface soils results in vapor phase <br /> perr._�ation and transport. Should these chemicals reach the water table and travel with the <br /> groundwater, vapors will continue to emanate from the contaminated groundwater into <br /> overlying soils. Thus, organic contamination of the subsurface soils or groundwater can be <br /> detected by measuring the relative concentration of volatile organics in the soil gas. <br /> Sampling locations for the soil gas survey were selected by superimposing an imaginary 20- <br /> foot grid over the existing tank area. The expected groundwater flow is to the southwest. <br /> Sample points were selected to encompass any groundwater flow in and around the old tank <br /> excavation, therefore locations were weighted heavily in the downgradient direction (Figure <br /> 2). Also, as analytical data were received, additional sampling locations were added to <br /> estimate the outer Iimits of the contamination plume. <br /> Soil gas samples were collected with a sampling probe consisting of 3/4-inch galvanized <br /> pipe tipped with a reusable aluminum point. A probe was driven inti the ground at each <br /> sampling Iocation to a depth of 5 to 13 feet below Iand surface using aTruck-mounted, <br /> hydraulically-actuated point driver. The probe was then pulled up 6 inches to expose the <br /> sampling interval. A regulated vacuum pump was attached to the probe with a teflon tube <br /> adaptor. A minimum of 2 to 5 liters of soil gas were purged to ensure that a representative <br /> soil gas sample would be collected. The samples were collected by withdrawing the soil gas <br /> T from a short piece of connecting silicon rubber tube using a calibrated glass syringe. <br /> Duplicate samples in volumes ranging from 1 ml to 2 ml, depending on the VOC <br /> W concentration, were also collected. All holes left in the ground or pavement surface from the <br /> soil gas point removal were filled with neat cement. <br /> 3 <br />