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G �� - --.v 's"��� - - _ - - _ _ - y-�kyP n-.`.a; _ - s'�+••-. .� ,sir-bar <br /> I Sample Description <br /> r-- See attached Sample Description Information. <br /> The samiles were received under chain-of-custody, <br /> II - Analysis Request <br /> The following analytical tests were requested. <br /> Lab ID Analysis Descri tion <br /> 044405-0001 an 2 Total Petroleum Hydrocarbons <br /> Benzene, Toluene, Ethyl Benzene and Xylenes <br /> III _Quality Control <br /> A. Proect Specific QC. No project specific QC (i.e., spikes and/or <br /> duplicates) was requested. <br /> B. Method Blank Results. A method blank is a laboratory-generated <br /> sample which assesses the degree to which laboratory operations <br /> and procedures cause false-positive analytical results for your <br /> samples. <br /> No target parameters were detected in the method blanks associated <br /> with your samples at the reporting limit levels noted on the data <br /> sheets in the Analytical Results section. <br /> C. Laborator Control Samples. An LCS is a well-characterized matrix <br /> (blank water, sand or ce ite) which is spiked with certain target <br /> parameters and analyzed at approximately 10% of the sample load in <br /> order to establish method-specific control limits. The LCS <br /> results associated with your samples are on the attached <br /> Laboratory Contrnl Sample Report. <br /> Accuracy is measured by Percent Recovery as in: <br /> % recovery = measured concentration! x 100 <br /> (actual concentration <br /> Precision is measured using duplicate tests by Relative Percent Difference <br /> (RPD) as in: <br /> RPD = � recover test 1 - % recovery test 2) x 100 <br /> (X recovery test 1 + t recovery test 2 /2 . <br /> Control limits for accuracy (percent recovery) are based on the average, <br /> historical percent recovery +/-3 standard deviation units. Control limits <br /> for precision (relative percent difference) range from .0 (identical <br /> duplicate LCS results) to the average, historical reidtive percent <br /> difference + 3 standard deviation units. These control limits are updated <br /> on a quarterly basis. In cases where there is not enough historical data, <br /> EPA limits or advisory limits are set, with the approval of the Quality <br /> Assurance department. <br /> v <br />