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Concentration limits for the facility may be updated annually for interwell comparisons to <br /> provide ongoing definition of water quality for the facility. The tolerance limits for the <br /> new wells will be prepared after eight data points are obtained. <br /> With the exception of pH, analytical data for the monitoring parameters will be compared <br /> to the upper concentration limit; an exceedance of an upper concentration limit may be <br /> indicative of a release from the landfill. Both an upper and lower concentration limit will <br /> be calculated for pH; pH values that fall below the lower limit or exceed the upper limit <br /> may be indicative of landfill impact. <br /> Because the performance standard for data evaluation is to provide a reliable indication <br /> of a release, the following procedures will be used to evaluate naturally occurring <br /> (i.e., inorganic constituents) monitoring parameters and COCs. The following procedures <br /> are considered necessary because naturally occurring compounds may not provide <br /> unambiguous indications of a release. <br /> During each monitoring event, the analytical results for the naturally occurring <br /> monitoring parameters will be evaluated, and a list of parameters will be compiled that <br /> meets the following criteria: <br /> • The naturally occurring monitoring parameter, or COC, is detected at a <br /> concentration which exceeds its concentration limit (or falls below in the case of <br /> pH). <br /> • The naturally occurring monitoring parameter, or COC, is not detected in the <br /> laboratory quality control samples. <br /> If two or more naturally occurring monitoring parameters or COCs that meet these <br /> criteria are detected in samples from the detection monitoring points in groundwater <br /> during a monitoring event, tentative indication of a release will be considered. <br /> For the purposes of identifying a release, TDS and EC will not be considered separate <br /> monitoring parameters because they both test for the same constituent (i.e., total ionic <br /> species in solution). In addition, because TDS and EC measure the total ionic species in <br /> solution, an increase in one parameter (e.g., chloride) may cause a correlated increase in <br /> TDS and EC. Observations of this nature will be closely scrutinized. Concentration of <br /> TDS, EC, and one major ion may not be considered a tentative indication of a release. <br /> Surface Water — Because of the limited amount of surface water data, concentration <br /> limits for the surface water cannot be calculated by the tolerance limit method as <br /> described above. In addition, because the surface water features are intermittent streams <br /> that are normally dry,the chemical makeup of the water can change significantly between <br /> flow events. For that reason a compound specific concentration limit cannot be defined <br /> at this time for inorganic constituents. However, the indication that a release has <br /> occurred will be assessed with each monitoring event in which continuously flow water is <br /> present between both the upstream (SW-1) and the downstream (SW-2) monitoring <br /> points. If the chemical concentration of any inorganic parameter is significantly higher at <br /> Foothill WQPS Rev Ldoc <br /> 4-4 <br />