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Site Investigation Work Plan Data Acquisition Carousel Cleaners, Sacramento, California and QA/QC 5.3.2 Accuracy Accuracy is a measure of bias in a measurement system. The closer that the value of the measurement agrees with the true value,the more accurate the measurement. This value will be expressed as the percent recovery for any spikes (LCSs and surrogates)as well as calibration recoveries. 5.3.3 Representativeness for Standard Reference Material Representativeness is a qualitative parameter that expresses the degree to which sample data accurately and precisely represent a characteristic of a population,variations at a sampling point, or an environmental condition. The purpose for sampling, selection of the sampling locations,number of samples to be collected, ambient conditions, frequencies and times for sample collection, and sampling techniques have been designed to ensure that the environmental conditions will be sufficiently represented. 5.3.4 Comparability Comparability is a qualitative parameter expressing the confidence with which one data set can be compared to another. Sample data will be collected and reported consistently,to be comparable with other measurement data for similar site samples and sample conditions. This goal will be achieved by using standard operating procedures to collect and analyze representative samples,reporting analytical results in appropriate and consistent units, and meeting similar accuracy and precision acceptance criteria. 5.3.5 Completeness Completeness is defined as the percentage of valid measurements to planned measurements.Valid data are values that are not rejected for any reason, including deviations from QC requirements. An objective of the sampling program is to establish the quantity of data needed to support the investigation. This objective will be achieved by obtaining samples for all types of analyses required at each individual location; a sufficient volume of sample material to complete the analyses; samples that represent all possible contaminant situations under investigation; and samples at critical data locations, such as background and control samples. Completeness will take into consideration adverse environmental conditions and the potential for justifiable change with respect to schedule and sample locations. The completeness goal for this project is 90 percent. 5.4 Quality Control Samples and Procedures 5.4.1 QC Checks The QC checks of both field and laboratory sample analysis will be used to assess and document data quality, and to identify discrepancies in the measurement process that need correction. Field QC samples may consist of field replicates(duplicates),trip blanks, and temperature blank samples. Laboratory QC may consist of method calibration,LCS,method blanks, surrogate spikes, and matrix spike/matrix spike duplicate samples. The analytical laboratory also will report any QC failures, such as calibration check samples that exceed control limits. 5-2