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■1Z1 INC <br /> Is 4 There was some evidence to suggest the action of natural biodegradation of <br /> petroleum hydrocarbon attenuation within the shallow water zone This was <br /> suggested by the reported significant discrepancy between calculated groundwater <br /> flow velocity and the distance petroleum hydrocarbon contamination has moved in the <br /> down-gradient direction <br /> 5 The anticipated groundwater remediation program proposed by McLaren (1989b) was <br /> planned to include hydraulic control and recovery of petroleum hydrocarbon- <br /> contaminated water As groundwater levels were anticipated to rise to shallower <br /> levels through natural fluctuation, any remaining hydrocarbons on soils which desorb <br /> and dissolve in the groundwater would be recovered by the groundwater treatment <br /> system <br /> 8 2 Groundwater Remediation <br /> The work by McClaren (1989b) and two subsequent quarterly sampling rounds conducted <br /> by WaterWork Corp indicated an area of dissolved petroleum hydrocarbons in <br /> groundwater at the site immediately below and adjacent to the former tank location No <br /> evidence of free product was found to be present in any of the monitoring wells (McLaren, <br /> 1989a) The estimated extent of dissolved petroleum hydrocarbon impacted area included <br /> the former tank pit and extended down-gradient approximately 70 to 100 feet (Exhibit 7) as <br /> estimated by McLaren (1989a) <br /> Recove of Dissolved Hydrocarbon Constituents <br /> The planned primary element of the groundwater remediation program at the site was the <br /> hydraulic control scheme The proposed recovery well operation was based on the data <br /> developed from the short-term pumping test conducted by WaterWork (1990) However, <br /> as pointed out by WaterWork (1990), short-term data are inherently suspect and the <br /> recovery rates must be adjustable to reflect long-term aquifer response <br /> 19150011005 32 <br />