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2.14 Discussion of Why Background is Unattainable Using Best Remedial Methods <br /> A minor amount of degraded petroleum compounds were present in soil/aquifer samples <br /> collected in 2003. Groundwater monitoring data shows that dissolved concentrations <br /> have declined to below chemical analytical detection limits. On this basis the <br /> groundwater is at "background" levels (contaminants not detected) in all monitoring <br /> wells. <br /> -,,,.2.15 Discussion and Estimate of Remaining Contaminant Mass in Soil and <br /> Groundwater Versus Contaminant Mass Removed <br /> The rough estimate of contaminant mass remaining in soil the vicinity of MW-2 is about <br /> six gallons TPHG and zero gallons Benzene. The rough estimate of TPHD contaminant <br /> mass remaining in soil the vicinity of MW-2 is about 57 gallons. <br /> The rough estimate of TPHG remaining in groundwater is zero gallons TPHG and <br /> Benzene. The rough estimate of TPHD remaining in groundwater is zero gallons. <br /> 2.16 Assumptions, parameters calculations and model used in any risk assessments <br /> (SOIL VAPOR ASSESSMENT) <br /> A soil vapor assessment was not performed for this site. <br /> 2.17 Assumptions, parameters calculations and model used in any risk assessments <br /> (GROUNDWATER FATE AND TRANSPORT) <br /> A groundwater fate and transport model was not performed for this site. The dissolved <br /> plume has remained near the edge of Delta Disposal. The plume size has decreased <br /> markedly from 2008 through 2009 to non-detected levels as shown in the historic well <br /> \ monitoring data. <br /> �1 2.18 Rationales why the conditions remaining at the site will not adversely impact <br /> water quality,human health and safety and other beneficial uses. <br /> The underground fuel storage tank source and residual soil contaminants have been <br /> removed from the property. Groundwater monitoring wells and quarterly monitoring has <br /> been ongoing since 2009 and has documented the position of the dissolved plume on the <br /> property and northerly groundwater flow direction. The dissolved plume has diminished <br /> to non-detected levels as shown in the historic well monitoring data. Further <br /> groundwater water quality problems are not anticipated from this plume on this basis. <br /> A 2000-foot well search was conducted in 2003. That survey showed that there were no <br /> drinking water wells in the project site area. The shallow aquifer in which the dissolved <br /> plume occurs is not known to be a drinking water aquifer nor is it used for any other <br /> water source according to Wright's information. Historic groundwater monitoring has <br /> shown the dissolved plume to be stable with little to no net downgradient movement and <br /> Page 8 of 17 <br />