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window, actions will be taken to correct the problem. The instrument must be recalibrated after any retention-time window failure and affected samples must be reanalyzed. 7.3 Method Detection Limits The method detection limit(MDL) is the minimum concentration of an analyte or compound that can be measured and reported with 99 percent confidence that the concentration is greater than zero. MDLs are established for each method, matrix, and analyte, and for each instrument used to analyze project samples. MDLs are derived using the procedures described in 40 Code of Federal Regulations 136, Appendix B (USEPA, 1990a). USEPA requires that MDLs be established on an annual basis. MDLs must be less than applicable reporting limits for each target analyte. A reporting limit(RL) of 0.5 micrograms per liter(gg/L)will be used for groundwater samples analyzed by USEPA Method 8260B and an RL of 0.005, µg/L in air will be used for soil vapor samples analyzed by USEPA Method TO-15 7.4 Instrument Calibration Analytical instruments will be calibrated in accordance with the procedures specified in the applicable method. All analytes that are reported should be present in the initial and continuing calibrations, and these calibrations must meet the acceptance criteria specified in the reference method. Records of standard preparation and instrument calibration will be maintained. Records should unambiguously trace the preparation of standards and their use in calibration and quantification of sample results. Calibration records will be traceable to standard materials as described in Section 5.1 .2. At the onset of analysis, instrument calibrations will be checked using all of the analytes of interest. `This applies equally to multiresponse analytes. At a minimum, calibration criteria will satisfy method requirements. Analyte concentrations can be determined with either calibration Environmental/LNC/workplan/Appendix3.wpd 19