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5 Data Quality Assessment The October 2018 data were assessed in accordance with the WQSAP (Dudek 2O17a). Data assessment procedures included review of quality control samples and sample custody documentation. 5.1 Water Levels The October 2018 water level measurements and field parameter data were assessed qualitatively for completeness and comparability to previous field data.The October 2018 field data were deemed satisfactory and usable based on this assessment. 5.2 Water Quality Laboratory analyses of groundwater samples collected in October 2018 were subjected to quality assurance/quality control evaluation. The evaluation included a review of the results of duplicate analyses, matrix spike recovery analyses, and holding times. The October 2018 analytical data for VOCs were deemed satisfactory and usable based on the data assessment. The October 2018 analytical data were also considered representative of groundwater quality at the site based on comparison with analytical data from September 1988 to the present. As part of quality control for the VOC analysis,4-bromofluorobenzene, dibromofluoromethane,and toluene-d8 were added as surrogates to each sample. Analytical results were compared to the known concentration of each surrogate and reported as a percent recovered. Percent recoveries for dibromofluoromethane all fell within the quality control limits of 76%to 132%. Percent recoveries for 4-bromofluorobenzene all fell within the quality control limits of 80%to 120°/x. Percent recoveries for toluene-d8 fell within the quality control limits of 80%to 128%.Thus, the data were deemed satisfactory. As part of quality control for the 1,4-dioxane analysis, 1,4-dioxane-d8 and nitrobenzene-d5 were added as surrogates to each sample. Analytical results were compared to the known concentration of each surrogate and reported as a percent recovered. Percent recoveries for 1,4-dioxane-d8 fell within the quality control limits of 30% to 120% in all samples analyzed. The associated method blank 1,4-dioxane-d8 surrogates were within quality control limits,and the percent recoveries of the nitrobenzene-d5 surrogates were within quality control limits for all samples analyzed. Therefore,the laboratory deemed the results acceptable. In addition to surrogates, matrix spike (MS), MS duplicate (MSD), and laboratory control samples were analyzed to assess accuracy. The MS/MSD percent recoveries for the site were within the quality control limits. Therefore,the data quality is deemed acceptable. MS/MSDs were analyzed by the laboratory to assess precision.All MS/MSD relative percent differences were within quality control limits.Therefore,the data quality is deemed acceptable. One field blank,one equipment blank,and one trip blank was collected duringthe October 2018 groundwater monitoring event. No VOCs were detected above the MDLs in any of the blanks. All samples analyzed for VOCs and 1,4-dioxane were analyzed within their holding times. D U D E K 10886-1 19 March 2019