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t <br /> Mr Lawrence H Beasley Project 22611-100 001 <br /> N July 18, 1997 <br /> Page 8 <br /> 1994 and groundwater plume appears to be stable and is limited to the area near the <br /> former UST complex Figure 11 presents the extent of dissolved hydrocarbons beneath <br /> the site Results of analyses are presented in Appendix A <br /> Based on subsurface investigations, the aquifer is comprised of silty to sandy silt The <br /> total pounds of 1 PHG presently in groundwater have been estimated using the average <br /> concentrations from wells MW-2 through MW-7 and VEW-1 (1,582 ppb or 1 582 ppm) <br /> collected during the first quarter 1997 sampling event The impacted surface is presented <br /> in Figure 1 i (approximately 49,851 ft2) The affected volume was estimated using a <br /> porosity of 35 percent (maximum porosity of sand, Fetter 1980) and density of water of <br /> 62 4 lbs/ft3 EMCON assumed that the entire water column observed in the monitoring <br /> wells (15 feet) to be impacted with hydrocarbons <br /> V 1=49,851 ft2 x 15 ft x 0 45 = 336,494 ft' <br /> Dissolved TPHG remaining= 1 582 mg/kg x 1 x 10 kg/mg x 62 4 lbs1W x <br /> 336,494 ft3 <br /> =33 21 lbs (approximately 5 gallons) <br /> Remediation <br /> CONCLUSIONS AND RECOMMENDATIONS <br /> EMCON recommends that a"No Further Action"status be granted based on the following <br /> • The source of contamination has been removed by excavation(UST removed in 1988) <br /> • Approximately 107 pounds of hydrocarbons have been removed by excavation and <br /> approximately 15,000 pounds of hydrocarbons have been removed via SVE <br /> • Approximately 5,492 pounds of hydrocarbons remain in soil and approximately <br /> 33 pounds(5 gallons)of dissolved hydrocarbons remain in groundwater <br /> • Dissolved hydrocarbon concentrations have decreased with time and groundwater <br /> plume appears to be stable and is limited to the vicinity of the former UST complex <br /> • There is no beneficial use of the first-encountered groundwater The nearest municipal <br /> well is currently inoperable and drinking water in this region is provided by reservoirs <br /> . In addition,the top of screen for municipal wells is approximately 260 feet bgs with a <br /> sanitary seal <br /> SACK 1261 ICLOS URE.-951dms I <br />