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WASTE DISCHARGE REQUIREMENTS ORDER NO. R5-2009-0049 -17- SAN JOAQUIN COUNTY DEPARTMENT OF PUBLIC WORKS HARNEY LANE LANDFILL SAN JOAQUIN COUNTY Monitoring Data Analysis 15. All monitoring data analysis methods shall be consistent with the performance standards specified in Section 20415(e)(9) and sampling standards specified in Section 20415(e)(12). 16. The statistical method shall account for data below the practical quantitation limit (PQL) with one or more statistical procedures that are protective of human health and the environment. Any PQL validated pursuant to Section 20415(e)(7) that is used in the statistical method shall be the lowest concentration (or value) that can be reliably achieved within limits of precision and accuracy specified in the WDRs for routine laboratory operating conditions that are available to the facility. Any Section 20415(e)(7) technical report submitted by the Discharger shall consider the PQLs listed in Appendix IX to Chapter 14 of Division 4.5 of Title 22, California Code of Regulations, for guidance when specifying limits of precision and accuracy. For any given constituent monitored at a background or down gradient monitoring point, an indication that falls between the MDL and the PQL for that constituent (hereinafter called a "trace" detection) shall be identified and used in appropriate statistical or nonstatistical tests. Nevertheless, for a statistical method that is compatible with the proportion of censored data (trace and ND indications) in the data set, the Discharger can use the laboratory's concentration estimates in the trace range (if available) for statistical analysis, in order to increase the statistical power by decreasing the number of"ties". Concentration Limits 17. Concentration limits (CLs) for corrective action monitoring shall be developed consistent with Monitoring Specifications E.18 through E.20 below. 18. For inorganic COCs for which at least 10% of the data from background samples equal or exceed their respective MDL (i.e., naturally occurring CDCs), the i Discharger shall use one of the following statistical data analysis methods for determination of CLs and detection of a release: a. Tolerance or Prediction Interval statistical-method; b. Analysis of Variance (ANOVA) statistical method; and/or c. An alternative statistical method authorized under Section 20415(e)(8) and approved by the Executive Officer under Section 20415(e)(7)). Background monitoring data shall be screened for trends prior to calculating CLs to ensure that the data represents a single statistical population (i.e., one that does not show appreciable variation per Section 20415(e)(10)). CLs shall be periodically updated, as necessary, to reflect current background conditions. If a significant trend is identified that reflects changes in background conditions, data prior to development of the trend shall not be included in updating s. Otherwise CLs shall include prior historical data. Statistical CLs shall also take into account 1 any seasonality in the data. Any'analyte that exceeds its statistical CL shall provide a preliminary indication [or, for a retest, measurably significant evidence] of a release at that monitoring point.