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•' - Laboratory Quality Assurance • Documentation of instrument performance checks • Documentation of instrument calibration • Documentation of the traceability of instrument standards, samples, and data • Documentation of analytical and QC methodology (QC methodology includes use of spiked samples, duplicate samples, split samples, use of reference blanks, and check standards to check method accuracy and precision) - Field Quality Assurance • Documentation of sample preservation and transportation • Documentation of field instrument calibration and irregularities in performance Internal laboratory quality assurance checks will be the responsibility of the contract laboratories. Data and reports submitted by field personnel and the contract laboratory will be reviewed and maintained in the project files. Tv es of Quality Control Checks Samples are analyzed using analytical methods outlined in EPA Manual SW 846 and approved by the California Regional Water Quality Control Board-Central Valley Region • in the Leaking Underground Fuel Tanks (LUFT) manual and appendices. Standard contract laboratory quality control may include analysis or use of the following: • Method blanks — reagent water used to prepare calibration standards, spike solutions, etc. is analyzed in the same manner as the sample to demonstrate that analytical interferences are under control. • Matrix spiked samples — a known amount of spike solution containing selected constituents is added to the sample at concentrations at which the accuracy of the analytical method is to satisfactorily monitor and evaluate laboratory data quality. • Split samples — a sample is split into two separate aliquots before analysis to assess the reproducibility of the analysis. • Surrogate samples — samples are spiked with surrogate constituents at known concentrations to monitor both the performance of the analytical system and the effectiveness of the method in dealing with the sample matrix. • Control charts — graphical presentation of spike or split sample results used to track the accuracy or precision of the analysis. • Quality control check samples — when spiked sample analysis indicates atypical instrument performance, a quality check sample, which is prepared independently of the calibration standards and contains the constituents of interest, is analyzed to confirm that measurements were performed accurately. Page 4