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CONESTOGA-ROVERS <br /> &ASSOCIATES <br /> areas enclosed by each of these lines are listed in Table D1and shown on Figure 5. Based on the <br /> approach and assumptions presented above,,the remaining mass of TPHd in_ soil is estimated at ' <br /> 91 pounds or 12 gallons. _ <br /> TPHg Mass in Soil: .:The average"concentration of TPHg in.soil.enclosed within the-l-mg/Kg <br /> isoconcentration line was conservatively estimated as.5 mg/Kg. .The average concentration of:. <br /> TPHg in soil enclosed within the 10-mg/Kg isoconcentration line.was conservatively estimated <br /> as 12 mg/Kg. The area: enclosed by.each of these lines are listed in.Table D2 and shown on <br /> Figure 6. Based on the'approach and assumptions presented above, the remaining mass.of TPHg <br /> in soil is estimated to be minimal.. <br /> MTBE Mass in Soil: The average concentrations of MTBE in soil enclosed within the 4-mg/Kg <br /> isoconcentration line was conservatively estimated.as.I mg/Kg. The area enclosed by this line is <br /> listed in Table D3 and"shown-on,Figure 5.'-Based on the'approach and d assumptions presented <br /> above,the remaining mass of MTBE in soil is estimated to be-minimal. <br /> TBA Mass in Soil: ,:-The-average concentrations of,TBA.in soil enclosed within the 1-mg/Kg <br /> isoconcentration line was.conservativelyestimated as 4 mg/Kg,eThe area enclosed by this line is <br /> `listed in Table D4:a6d.'shown on Figure 6.';Based_on.the approach and assumptions presented <br /> above,the remaining mass of TPHg in soil is estimated.to be minima-L.— <br /> Contaminant <br /> inimal.- ..Contaminant Mass in Groundwater" <br /> MTBE Mass in Groundwater: The'average concentrations of MTBE in groundwater enclosed <br /> A _ <br /> _ within the 1-µg/L isoconcentration line was conservatively estimated`as:4 µg/L. The area <br /> enclosed by this lineislisted in Table D5 and shown on Figure 7. The remaining mass of MTBE <br /> in groundwater is estimated'to be minimal. <br /> .14. Assumptions,parameters, calculations and model used_in-risk assessments, and fate and <br /> transport modeling; <br /> Not applicable; no models were=used. Y Ari`evaluation-of soil-vapor,intrusion to indoor air is <br /> provided in Attachment-E Based on &-conservative comparison�of site data.to ESLs, this site <br /> passes the Tier 1 analysis,which.indicatesthat residual levels of gasoline'constituents in soil and <br /> groundwater beneath the site do not pose's threat to indoor`air-quality. <br /> 0813 10 <br /> Worldwide Engineering, Environmental,Construction,and IT Services <br /> w ` r <br />