2011-08-08_REVISION - M1977493 (36)

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• • Water Quality Monitoring Plan Climax Molybdenum Company Version: R1 Permit No. M -1977 -493 After collection of the baseline data, if graphical trends do not suggest declining water quality, no quantitative trend evaluation is needed. However, a trend that does suggest increasing concentrations in parameters will require a more rigorous statistical analysis and further actions by Climax to prevent potential impacts to the receiving water. The approach to determining whether there is a temporal trend will involve the following steps: 1. Based on temporal plots of the parameters of concern, define a window of time for evaluating whether a trend exists. 2. Develop an approach that corrects for the effects of seasonal effects and that is protective of the receiving waters. In other words, if seasonal peaks occur in concentrations, the evaluation should be performed to determine if there are trends in the peak concentrations. 3. Compare the most recent 4 sampling results against the 80th percentile upper prediction limit (UPL). If four consecutive sample results exceed the UPL this fact will be considered along with the other factors in the trend evaluation. Calculation of the 80th percentile UPL will be done using the one -sided Student t test equation (as presented in Section 5.1.2; with a =0.20 and substituting the mean for the NPL for the baseline dataset). 4. If a statistical test for a trend is needed, approaches such as Sen's or Mann - Kendall tests (Gibbons, 1994) will be used, if a sufficient number of samples are available to apply these tests. 5.2.3.2 Outlier Identification Outlier results can and do occur in environmental monitoring. Because monitoring of internal monitoring sites is being performed to detect changes in the water quality that may impact uses of Eagle Park Reservoir or Clinton Reservoir, a careful evaluation of the data will be necessary. The general practice will be to not remove outliers from the water - quality database, but to consider them in the visual and statistical trend evaluations. However, Climax will perform outlier testing using Rosner's outlier or other applicable test, considering the size of the available sample set and the validity of statistical tests for the circumstance, and report the results in its annual monitoring report. Test results identified as `outlier" will be maintained in the monitoring database. 5.2.3.3 Increase Monitoring Frequency If recent sampling results suggest that the water quality may be declining, in consideration of the evaluations described in Section 5.2.3.1, the sampling frequency at the identified sampling site may be increased to monthly, to better define changes that may be occurring. Samples will be collected during the period of the year when weather and site conditions allow access. This more frequent sampling schedule will be maintained until DRMS and Climax agree that the sampling period can be lengthened. For example, if monthly monitoring shows that the poorer quality sample was a temporary excursion and not indicative of a longer term trend, there would not be a need to continue the monthly sampling. Similarly, if the monthly sampling demonstrates that a trend is occurring and the data indicate that the trend is relatively consistent, quarterly or biannual sampling would be appropriate to monitor its behavior. EPP — Appendix C August, 2011 20