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Trace concentrations of VOCs were reported in groundwater samples collected from MW-1 and <br /> MW-2 during 2002 monitoring. In most cases, the detected constituents were also found in one <br /> or more QC blanks, and were therefore considered"false positive"results. No resampling was P <br /> required during the 2002 monitoring period. <br /> Only two VOCs(which were not also detected in a QC blank)were detected in groundwater <br /> samples from MW-3 during 2002 (MTBE and 1,4-Dichlorobenzene). No resampling was <br /> requested due to the previous detections of VOCs in this well and the suspected release. <br /> Surface Water ' <br /> Only one surface water sample was collected during 2002,the"first storm" surface water <br /> samples. Statistical results from the"first storm" sampling event indicate an exceedance of the <br /> concentration limit for Total Suspended Solids(TSS) at sampling point S-2. However, <br /> concentrations of TSS in samples from S-1 and S-2 were much higher than any previously <br /> recorded concentration. Also,the concentration of TSS at the upgradient point(S-1)was greater <br /> than the concentration at the downgradient point (S-2). This is consistent with historical data in <br /> which the mean and median concentrations of the upgradient point are greater than those of the <br /> downgradient point. These results lead the County believe that there is no impact from the <br /> landfill on surface/storm water. TSS concentrations will be monitored accordingly per the <br /> WDRs. All other reported concentrations of constituents were below established concentration ' <br /> limits. <br /> HISTORICAL TIME SERIES PLOTS <br /> Historical Time Series Plots are located in Appendix F. Note that constituents that are not <br /> detected are plotted at a value of half their respective detection limits. Some outliers were ' <br /> removed from data sets containing general water quality parameters (i.e. TDS, Chloride,Nitrate, <br /> Sulfate,pH, EC,Turbidity)prior to plotting. No outliers were removed from data sets containing <br /> VOCs or COCs (Metals). ' <br /> MONITORING ANALYTICAL DATA , <br /> Historical groundwater and surface water monitoring data is contained on the attached diskette. <br /> The disk contains Excel files and Sanitas compatible text files in tab-delimited format. The text <br /> files can be used for statistical analyses. <br /> Foothill Sanitary Landfill Department of Public Works/Solid Waste t <br /> e Quarter and Annual 2002 Groundwater Monitoring Report H-2 County of San Joaquin <br />