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x._1.2 Isoconcetttration:Mans Estimate of"zero line"of Dissolved Plunu <br /> i:econnaissance BoBarings and hfionitoring Welt P{acemetit <br /> Wright drilled and sampled four exploratory borings at the site in 200.3; one in the former <br /> tank pit location, and the remainder spread in the assumed down and cross gradient. flow <br /> directions. The results of the soil sand groundwater chemical analyses are presented in <br /> Tables 2 and 3. A second set of borings was drilled in 2008 to further characterize the <br /> site. Information collected during the 2003 and 2008 investigations indicated that <br /> t9issolved TPHD contaminants were present in groundwater below the site, and the <br /> tastribution indicated a north-northwesterly groundwater movement. Wright presented <br /> this information to HHD and the one monitoring well location was selected adjacent to <br /> the location of Boring B-5. <br /> groundwater Flow Direction and Monitoring Results <br /> Groundwater monitoring data collected in 2009 and 2010 indicates the flow direction <br /> below the site is northwesterly. The CH2M monitoring wells located in the shallow <br /> aquifer were used in conjunction with well MWWES-I to establish groundwater flow <br /> direction, but not for analysis of petroleum hydrocarbon constituents. Groundwater <br /> raonitoring events were conducted at the site in 2009 and 2010. Groundwater collected <br /> H 2009 was reported to contain a TPHD concentration just over the detection limit. <br /> TPHD was not reported in groundwater collected from the site in 2010. TPHG and <br /> fITEX were not detected in any of the groundwater sampling events. <br /> 1-1 summary, site delineation was performed using data collected from the nine <br /> reconnaissance borings and one groundwater monitoring well. Wright recommended <br /> consideration for closure following the 2010 monitoring,. A CSR was requested by the <br /> EHD in their letter dated September 23,2010, <br /> 2.13 Summary of Remedial hhthods for Soil and Groundwater <br /> Site cleanup in 1998 included UST source removal, excavated soil was returned to the <br /> excavation. No groundwater was pumped from excavation. <br /> 2.14 Discussion of 3Yhy IftackgmalldUnattainable Using Best Reinedial Method's <br /> 7 he UST tank removal and soil excavation was performed in 1998. Only TPHD has been <br /> detected in groundwater samples collected from this site, TPHG, BTEX, and fuel <br /> oxygenates do not appear to be present. Groundwater collected from MWWF.S-1 <br /> contained 51 ug/l TPHD only in 2009. No dissolved petroleum hydrocarbon constituents <br /> were detected in 2010. On this basis in our opinion the"background" of groundwater has <br /> been attained at the monitoring well. <br /> 4W)/CSR/Rept Page 8 of 17 <br />