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HHk-22-1955 18:55 GftHDIEPtT P.02/06 Gradient corporation MEMORANDUM To: Lisa W. Kaul, EPC Date: March 22, 1995 From: Lisa Kulju Krowitz Subject: Data Quality Assessment for data collected at Lincoln Center in Stockton, California cc: Mike Buck, Riddle & Isola Susan Chaprdck, Gradient Corporation A data usability assessment was performed on the volatile organic data for the 20 aqueous samand the associated field QC samples (2 equipment and 6 trip blanks) collected at Lincoln Center in Sples Stockton, fic Analytical Laboratory. The data usability assessment California. All samples were analyzed by Paci focused on only the main chemicals-of-concern at the site: tetrachloroethylene, trichloroethylene, and dichloroethylene (including 1,1-dichloroethylene, cis-1,2-dichloroethylene, and trans-1,2- dichloroethylene). The primary objective of the data usability assessment is to make known and quantify, where applicable, the uncertainty in the data such that the end user is aware of potential biases, false positives, and false negatives in the analytical data. Qualifiers are applied to the data during the usability assessment process to flag these uncertainties. Data that are unqualified or qualified "U" (not detected), a "d" (estimated), or "U1" (estimated detection/quantitation limit) are usable for project decisions. Data qualified "R" (rejected) are unusable as the level of uncertainty in the value is unacceptable for basing project decisions, risk calculations, or litigation. During the data usability assessment three of the six key indicators of data quality, as described in USEPA guidance, as affected by analytical laboratory procedures were evaluated. These included: accuracy, precision, and sensitivity. Due to insufficient project information, three other data quality indicators including representativeness, comparability, and completeness could not be evaluated during this assessment. The data were assessed based on the National Functional Guidelines for Evaluating Organic Analyses 1988, Guidance for Data Usability in Risk Assessment (Part A), Publication 9285.7-09A 1992, USEPA SW-846 Method 8260for Volatile Organic Analysis,and Gradient's professional judgment. The following quality assurance/quality control (QA/QC)parameters were evaluated during the data usability assessment review: Holding times to assess the accuracy of the results. Method, trip, and equipment blank results to assess laboratory and field contamination. Matrix spike and matrix spike duplicate(MS/MSD) recoveries to assess accuracy of the results relative to laboratory performance and specific sample matrix. g!1propcts\dq\9504100,mem r Gradient Corporonon