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WASTE DISCHARGE IREMENTS ORDER NO. -10- SAN JOAQUIN COUNTY FOR POST-CLOSURE AND CORRECTIVE ACTION MONITORING CORRAL HOLLOW SANITARY LANDFILL SAN JOAQUIN COUNTY selected from among those methods which would provide valid results in light of any matrix effects or interferences. 11. "Trace" results -results falling between the MDL and the practical quantitation limit (PQL) - shall be reported as such, and shall be accompanied both by the estimated MDL and PQL values for that analytical run. 12. MDLs and PQLs shall be derived by the laboratory for each analytical procedure, according to State of California laboratory accreditation procedures. These MDLs and PQLs shall reflect the detection and quantitation capabilities of the specific analytical procedure and equipment used by the lab, rather than simply being quoted from USEPA analytical method manuals. In relatively interference-free water, laboratory-derived MDLs and PQLs are expected to closely agree with published USEPA MDLs and PQLs. 13. If the laboratory suspects that, due to a change in matrix or other effects,the true detection limit or quantitation limit for a particular analytical run differs significantly from the laboratory-derived MDL/PQL values,the results shall be flagged accordingly, along with estimates of the detection limit and quantitation limit actually achieved. The MDL shall always be calculated such that it represents the lowest achievable concentration associated with a 99% reliability of a nonzero result. The PQL shall always be calculated such that it represents the lowest constituent concentration at which a numerical value can be assigned with reasonable certainty that it represents the constituent's actual concentration in the sample. Normally, PQLs should be set equal to the concentration of the lowest standard used to calibrate the analytical procedure. 14. All QA/QC data shall be reported, along with the sample results to which they apply, including the method, equipment, analytical detection and quantitation limits,the percent recovery, an explanation for any recovery that falls outside the QC limits,the results of equipment and method blanks,the results of spiked and surrogate samples, the frequency of quality control analysis, and the name and qualifications of the person(s)performing the analyses. Sample results shall be reported unadjusted for blank results or spike recoveries. In cases where contaminants are detected in QA/QC samples (i.e., field, trip, or lab blanks),the accompanying sample results shall be appropriately flagged. 15. Unknown chromatographic peaks shall be reported, along with an estimate of the concentration of the unknown analyte. When unknown peaks are encountered, second column or second method confirmation procedures shall be performed to attempt to identify and more accurately quantify the unknown analyte.