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m . taafte ae <br /> i <br /> 2.0 Background and Previous Investigations <br /> 36Is located in the northeast portion mishaps within the eastern North Balloon area and near <br /> the northeast comer of former Building that (Figure 1). One ZOOM lion diesel fuel UST was removed <br /> mom SHAD-136 in Aprl1100. Although soil and groundwater investigations were conducted at SHAD-06 <br /> between 19W and 2003, the site was net formally dosed by the CMD. In 2014 and 2015, additional snit, <br /> and groundwater Investigations were conducted at SHAD-136, to determine whether residual <br /> i eontam nation existed and, if sty, the concentrations and extent. Free duct was identifiedinthe son <br /> Fares A two soll sample lommons, DP0137 and DPO138 (Figure 2), In 2014, but was not delineated. Mom <br /> information on the 2014 SHAD-136 invmtiptbn is reported in the FieldSomplisB eeportfor USTs 12, 147,, <br /> 148, and Former Amfing stares Arco(uu, 2015al.Additionalinvestigations, Including uF measurements; <br /> (Appendix A), free product monitor m, and groundwater monitoring were conducted in 2015 Duane 3 <br /> and Figure al, to evaluate the extent and mobility of free product at SHAD-136. <br /> Up resuhs indicated the presence of free product in soil in a limited area at SHAD-136 <br /> (Figuree2). Monforingwell MW335Awas installed In May20151n the thickest portion ofthefree product <br /> plume, based on the LIF measurements. From May 29 until September 10, 2015, monmdng for the <br /> accumulation of free product was performed at MW335A. TPH and TPH-related compounds were <br /> detected In groundwater at MW335A: however, neither free product nor a TPH sheen was observed in <br /> Unwell. The free product mass appears to be immobile and does not pose a threat in downgradlent wells. <br /> Under the CAVB low threatclosure polity, groundwaer-specific criteria at SHAD-136 were met as <br /> described In a Memorandumtothe Site File (Appendix B). Free product was ldentlBed in sail between lA <br /> and la it and poses no risk from the direct ntact exposure pathway, unless deep excavation Is <br /> m perfo ed.Fi co <br /> gures 3 and A show the estimated vertical event of free product at SHAD-136. In addition, <br /> concentrations of ban toluene, ethNben: n and xylene (BTFx)compounds and naphthaleneson <br /> 1 ( vapor wereless than the B low-threat closure polity vapor Invaso ncentration critria for <br /> residential use, and no buildings exist or are planned at SHAD-136. However, SHA4136 cannot currently <br /> be considered as a low-threat because free product is present ((sWe, 2012). Therefore, W 6 need to he <br /> implemented at SHAD-136 to prom human health from residual free product and TPH concentrations <br /> in soil. <br /> AMm En msmem , <br />