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April 20, 1990 <br /> GROUND-WATER SAMPLING AND ANALYSIS <br /> Ouality Assurance/Ouality Control Obiectives <br /> The sampling and analysis procedures employed by Gettler-Ryan Inc. <br /> (G-R) for ground-water sampling and monitoring follow specific Quality <br /> Assurance/Quality Control (QA/QC) guidelines. Quality Assurance <br /> objectives have been established by G-R to develop and implement <br /> procedures for obtaining and evaluating water quality and field data <br /> in an accurate, precise, and complete manner so that sampling <br /> procedures and field measurements provide information that is <br /> comparable and representative of actual field conditions. Quality <br /> Control (QC) is maintained by G-R by using specific field protocols <br /> and requiring the analytical laboratory to perform internal and <br /> external QC checks. It is the goal of G-R to provide data that are <br /> accurate, precise, complete, comparable, and representative. The <br /> definitions for accuracy, precision, completeness, comparability, and <br /> representativeness are as follows: <br /> - Accuracy - the degree of agreement of a <br /> measurement with an accepted referenced or true <br /> value. <br /> - Precision - a measure of agreement among <br /> individual measurements under similar <br /> conditions. Usually expressed in terms of the <br /> standard deviation. <br /> - Completeness - the amount of valid data obtained <br /> from a measurement system compared to the amount <br /> that was expected to meet the project data <br /> goals. <br /> - Comparability - expresses the confidence with <br /> which one data set can be compared to another. <br /> - Representativeness - a sample or group of <br /> samples that reflects the characteristics of the <br /> media at the sampling point. It also includes <br /> how well the sampling point represents the <br /> actual parameter variations which are under <br /> study. <br /> As part of the G-R QA/QC program, applicable federal, state, and local <br /> reference guidance documents are followed. The procedures outlined in <br /> these regulations, manuals, handbooks, guidance documents, and <br /> journals are incorporated into the G-R sampling procedures to assure <br /> that; (1) ground-water ' samples are properly collected, (2) <br /> ground-water samples are identified, preserved, and transported in a <br /> manner such that they are representative of field conditions, and (3) <br /> chemical analysis of samples are accurate and reproducible. <br /> 7tgeffler — ryan inc. (415)783-7500 Page 6 <br /> .. general and environmental conlraclors <br />