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7.0 CALIBRATION PROCEDURES AND FREQUENCY Calibration of instrumentation is required to ensure that the analytical system is operating correctly and functioning at the proper sensitivity to meet established reporting limits. Each instrument is calibrated with certified standard solutions and the linear range established for the analytical method. The frequency of calibration and the concentration of calibration standards is determined by the manufacturer's guidelines, the analytical method,or the requirements of special contracts. 7.1 GAS CHROMOTOGRAPHY(GC) -ORGANICS Quantification for samples that are analyzed by GC with element selective detectors shall be performed by external standard calibration. Standards containing the compounds of interest will be analyzed at various concentrations (minimum five levels) to establish the linear range of the detector. All calibrations must be performed using either average response factors or first-order linear regression (with a correlation coefficient requirement of> 0.995). Higher order fits will not be allowed. The resulting calibration curves must meet all method-specified criteria prior to sample analyses. The calibration curve or average response factor must be verified at the beginning of each day and at every tenth injection by a single point calibration standard. The response from the single point calibration standard will be checked against the average response factors or calibration curve established during initiation calibration. If deviations in the standard response are greater than those allowed by the method protocols, then a new calibration curve must be prepared. 7.2 CALIBRATION-WET CHEMISTRY Quantification of samples that are analyzed by ion chromatography or wet chemistry techniques will be performed by external standard calibration. A calibration blank and at least three calibration standards will be analyzed to establish the analytical curves. Continuing calibration checks and calibration blank analyses must be performed at a minimum frequency of 10 percent and after the last analytical sample. Initial and calibration verification results must fall within the control limits of 90-110 percent. 7.3 FIELD INSTRUMENT CALIBRATION Calibration of field instruments will be conducted daily whenever used during the sampling program. The field equipment will be maintained, calibrated and operated in a manner consistent with the manufacturer's guidelines and USEPA standard methods. 031090-10(4) -11- CONESTOGA-ROVERS&ASSOCIATES