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Groundwater Monitoring ARCADIS Report for the Semiannual Period from January 1 through June 30,2012 Lincoln Center,Stockton, California approximate southern crossgradient extent of the A-zone plume is defined by the non-detectable concentration of Hazardous Substances at MW-001A,and by the non-detectable/low-reported concentrations of Hazardous Substances at MW-003A, GEW-004A,and GEW-003A during the December 2011 sampling event.The A-zone plume of reported Hazardous Substances is approximately 1,100 feet wide near the eastern property boundary of Lincoln Center. Distribution of PCE and Total Hazardous Substances in B-Zone Groundwater Figures 10 and 11 illustrate the estimated distribution of PCE and total Hazardous Substances,respectively,in B-zone groundwater.The contours shown on these figures were developed using laboratory analytical data from groundwater samples collected during the December 2011 and June 2012 sampling events;however,only June 2012 sample results are plotted. During the June 2012 sampling event,the highest B-zone concentrations of PCE(6,000 pg/I)and total Hazardous Substances(6,399 pg/l, estimated)were reported in MW-215B. Figure 11 illustrates the extent of Hazardous Substances reported in B-zone groundwater.The estimated northern crossgradient is bounded by non-detectable concentrations of Hazardous Substances in monitoring well MW-200B(located at Lincoln Elementary School).The estimated southern crossgradient of the B-zone plume is defined by the non-detectable concentrations of Hazardous Substances measured in monitoring well MW-2048.The upgradient(western)extent of Hazardous Substances in the B-zone is defined by non-detectable concentrations of Hazardous Substances measured in monitoring well MW-0208,which is located on the western edge of the Lincoln Center property.The approximate downgradient(eastern)extent of the B-zone plume is near Inglewood Avenue,and is defined by the non-detectable concentrations of Hazardous Substances in well MW-212B.The B-zone plume of detected Hazardous Substances is approximately 1,400 feet wide near the eastern boundary of the Lincoln Center property. 2.3.2 Other VOCs This section presents a summary of VOCs,other than the Hazardous Substances, detected in groundwater samples collected at the Site from 1995 to date.A review of historical data indicates that chloroform has been reported most frequently in samples from monitoring wells.A summary of other VOCs detected in groundwater samples during the reporting period is presented in Table 3.A historical summary of VOCs,other than the Hazardous Substances,detected in groundwater samples collected at the Site m Un d GWJ 912£M0061XO 8