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L <br /> LAugust 11, 2000 -8- 003-7170 <br /> Monitoring well sampling protocols are described in Appendix A. All samples collected and <br /> L transported to an analytical laboratory will be preserved in a refrigerated cooler and maintained under <br /> chain-of-custody protocols. <br /> 4.2 Concentration Limits and Background Determination <br /> r <br /> Background values for each monitoring parameter must be established as part of the monitoring <br /> program. Concentration limits will be established for each parameter. Concentration limits are used in <br /> the detection monitoring program and are not to exceed the background values. In conjunction with <br /> appropriate statistical procedures, concentration limits provide the basis for identifying a release from <br /> a source. <br /> 4.2.1 Synthetic Organic Compounds <br /> Concentration limits for synthetic constituents (volatile organic compounds) will be set at the method <br /> detection limit. Synthetic constituents are not naturally occurring, and their presence in ground water <br /> or surface water,are an indication of impact. <br /> 4.2.2 Inorganic Constituents <br /> Currently at the site, ground-water data from the site's background or upgradient well defines the <br /> background data set and provides the basis for data comparisons. However, at the site, conditions <br /> make such comparisons inappropriate because the monitoring data show that concentrations for <br /> several of the constituents, including EC, chloride, nitrate, calcium, magnesium, and sodium, are <br /> consistently distinguishable among the wells. Since there is no unambiguous evidence of impact(e.g., <br /> VOCs have not been confirmed in site wells) the consistent differences in concentrations may be due <br /> to natural geologically derived spatial variations in the water quality. Where spatial variations exist, <br /> intrawell comparisons should be made instead of using a single background well. In other words, each <br /> well should function as its own background. <br /> Because only one surface-water monitoring point (pond no. 3) is included in the monitoring program, <br /> intrapoint comparisons should also be performed. <br /> Concentration limits for the site will be established for each monitoring point using historical data for <br /> .� the individual monitoring points. The method selected to determine concentration limits is the <br /> tolerance interval statistical method which is described below. <br /> Concentration limits cannot yet be established for general water-quality parameters due to insufficient <br /> data. For the establishment of background values, Title 27, Article 1 requires analytical data from all <br /> background monitoring points for a period of 1 year (four quarters). When the background data sets <br /> are complete,concentration limits for the general water-quality parameters will be calculated. <br /> Concentration limits for monitoring parameters will be updated on a quarterly basis as part of routine <br /> monitoring for the site. <br /> 4.3 Statistical Evaluation Methods <br /> r The proposed concentration limits for synthetic organic compounds will be set at the analytical <br /> detection limit for the analysis. Since synthetic organic compounds are not naturally occurring, their <br /> presence in samples from a monitoring well is an indication of a release from the site. Therefore, <br /> ` Roo-37 dm Golder Associates <br />