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• <br /> Groundwater-to-indoor <br /> Air Screening Level <br /> Constituent (uglL) <br /> TPHg 586 <br /> Benzene 185 <br /> n-Butylbenzene* 2,000 ' <br /> sec-Butylbenzene* 3,940 <br /> 1,2-Dichloroethane 111 <br /> Ethylbenzene 161,000 <br /> lsopropylbenzene (cumene) 522 <br /> Methyl-tertiary butyl ether(MTBE) 13,000 <br /> Naphthalene 205 <br /> n-Butylbenzene 20,900 <br /> Toluene 49,100 <br /> 1,2,4-Tnmethyl benzene 1,510 <br /> 1,3,5-Tnmethyl benzene 1,580 <br /> Xylenes 16,200 <br /> * Screening level is equivalent to the solubility limit The model output indicated that the groundwater <br /> concentration at or above the solubility limit is not of concern for the vapor intrusion pathway <br /> Comparison of Screening Levels to Groundwater Concentrations , <br /> The screening levels derived above were compared to groundwater concentrations detected over the <br /> past year (July 2004 to April 2005) This time period was selected as it includes monitoring events <br /> covering all four seasons and represents a full year of data Because an active remediation system is <br /> in place, using data older than the period selected is not representative of current conditions <br /> Table A-1 presents the screening levels for each constituent and the analytical result for each <br /> constituent in each well sampled Concentrations exceeding the screening level are highlighted As <br /> shown in the table, the majority of concentrations are below the screening level, indicating that the <br /> constituent does not pose a risk to human health via the vapor intrusion pathway Therefore, the <br /> remediation of these specific wells and constituents is considered complete for the vapor intrusion <br /> pathway and monitonng is no longer necessary <br /> J'Proi ects10694015098-2931Worldng%ReportslLatter 2 July 2005 <br /> Requesting Reduction In SamplinglVapor Intrusion <br /> Pathway Evaluation-Letter doc ' <br />