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I <br /> (YVATC <br /> 1117 Lone Palm Avenue, Suite B <br /> Modesto, CA 95351 <br /> www.atcassociates.com <br /> 209-579-2221 <br /> A S S O C t A T E S I N C . Fax 209-579-2225 <br /> Environmental, Geotechnical and Materials Engineers <br /> concentration of 1 ,2-DCA was detected in the groundwater sample collected from MW3 . TBA <br /> r ' was detected in the groundwater samples collected from MW2, MW3 , and MW5 at <br /> `- concentrations ranging from 38 pg/L to 79 gg/L. The highest concentration of TBA was detected <br /> in the groundwater sample collected from MW5 . EDB was detected in the groundwater sample <br /> collected from MW8 at a concentration of 29 µg/L. Analytical results of groundwater samples <br /> are summarized in Table 3 . Laboratory data sheets and chain-of-custody documentation are <br /> _ contained in Appendix E. Isoconcentration maps depicting benzene, MTBE, and 1 ,2-DCA <br /> i concentrations in the groundwater samples collected from the shallow zone during the first <br /> ! <br /> quarter of 2008 are shown on Figures 8, 9, and 10, respectively. Isoconcentration maps depicting <br /> benzene and 1 ,2-DCA concentrations in the groundwater samples collected from the intermediate <br /> i <br /> zone during the first quarter of 2008 are shown on Figures 11 and 12, respectively. <br /> 5.0 GEOTRACKER DATA UPLOAD <br /> The monitoring well survey data were submitted electronically to the State Water Resources <br /> I Control Board (SWRCB) Geotracker database (confirmation numbers 4814543783 and <br /> 7247740805). Depth to water data and the laboratory analytical data associated with the first <br /> quarter 2008 sampling event were also submitted electronically to the SWRCB Geotracker <br /> database (confirmation numbers 2031666636 and 6538883924, respectively). Additionally, <br /> � ) boring logs assoiciated with MW16, MW17, MW18, and MW19 (confirmation numbers <br /> 64049521083 72744797465 9808104574, and 6880797445, respectively) were also submitted <br /> electronically to the SWRCB Geotracker database. Documentation of the data submittal is <br /> contained in Appendix F. <br /> 6.0 CONCLUSIONS <br /> The laboratory analytical results of the groundwater samples collected from monitoring wells <br /> !� MWl through MW6, MW8, MW9, and MW12 in March of 2008 are generally consistent with <br /> - recent historical analytical results of groundwater samples collected from these wells. MWl and <br /> MW8 located in the central portion of the site and MW6 in the southern portion of the site are the <br /> most impacted wells. The concentrations of benzene and xylenes increased, while the <br /> concentrations of toluene, ethylbenzene, 1 ,2-DCA, and GRO decreased in the groundwater <br /> sample collected from MWI with respect to the previous sampling event. The concentrations of <br /> BTEX, MTBE, GRO, EDB, and 1 ,2-DCA increased in the groundwater sample collected from <br /> MW8 with respect to the previous sampling event. The concentrations BTEX and GRO <br /> , l increased, while the concentration of 1 ,2-DCA decreased in the groundwater sample collected <br /> from MW6 with respect to the previous sampling event. The concentrations of BTEX and GRO <br /> detected in the groundwater samplecollected from MW6 represent historical highs for <br /> colle <br /> groundwater samples cted from _this well. The vertical extent of impacted groundwater <br /> beneath the site appears to be less than 120 feet bgs, based on data collected from previous <br /> sampling events. <br /> S:\Enviromental\28349Veports\lnv rpt 2008.doc 7 ATC Associates Inc. <br />