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EIS• <br /> 5 6 leA-1 <br /> Groundwater-to-Indoor <br /> Air Screening Level <br /> Constituent (ug/L) <br /> TPHg 58.6 <br /> Benzene 18.5 <br /> n-Butylbenzene* 2,000 <br /> sec-Butylbenzene* 3,940 <br /> 1,2-Dichloroethane 111 <br /> Ethylbenzene 161,000 <br /> Isopropylbenzene (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-Trimethylbenzene <br /> 1,510 <br /> 1,3,5-Trimethylbenzene 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 monitoring is no longer necessary. <br /> J:1Projecls\069401509B-293\Working\Reports{Letter 2 July,2005 <br /> Requesting Reduction in SamplingWapor Intrusion <br /> Pathway Evaluation-Letter.doc <br />