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i These samples monitor the laboratory's instrumentation, sample bottle storage facility, sample bottle preparation techniques, sample storage refrigerator, and glassware preparation cleanliness techniques. The laboratory maintains a written QA/QC Standard Operating Procedure (SOP) document that is available upon request. The SOP describes in-house procedures to ensure the quality of analytical activities. Where not otherwise specified for particular analytical methods, general internal quality control checks include the use of method blanks, surrogate spikes, matrix spikes, and duplicates. These quality control check techniques are described below. Method Blank Anal A method blank is a volume of deionized or distilled laboratory water, or, in the case of soil/sediment samples, a purified solid matrix. The laboratory will carry method blanks throughout the entire analytical scheme. Method blank volume or weight must be approximately equal to the sample volume/weight. The results of method blank analysis will not exceed the quantitation limits applicable to the particular analysis protocol and sample matrix. For method blank exceedences, the laboratory will take corrective action and document that action. The laboratory will re-extract, re-purge, and re-analyze all samples that the laboratory has processed with the faulty method blank. The laboratory will not use the results of method blank analysis to adjust or correct other sample data. Surrogate Spikes Surrogate compounds resemble sample analytes chemically, but rarely occur as species in the sample itself. The laboratory will perform surrogate spiking on all field and control samples in order to monitor preparation and analysis of samples prior to purging or extraction. Where the analytical method protocol identifies specific spiking solutions, the laboratory will use these solutions and will follow the relevant procedures if any sample or blank falls outside the surrogate spike limit criteria. Matrix Spikes and Duplicates/Spike Duplicates To assess analytical accuracy, the laboratory will automatically perform matrix spikes at frequencies appropriate for the specific analysis. To 5-4