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7.2.1 Field Duplicates <br /> Soil and sediment duplicate samples are actually co-located samples (i.e., samples collected as close to <br /> the same depth interval and proximity as possible). Field duplicates are handled, transported, and <br /> analyzed in the same manner as the other samples collected on the same day. Field duplicate testing may <br /> also be performed for headspace analysis of VOCs and other field measurements. The analytical results of <br /> field duplicate samples are used to assess the reproducibility of sampling procedures, sample handling, <br /> and analytical procedures. Duplicate samples collected in the field represent the heterogeneity of field <br /> conditions. Therefore, the precision estimates obtained from analysis of field duplicate samples are <br /> expected to have substantial associated variability. <br /> Duplicate soil vapor samples will be collected from the same temporary soil vapor probes into a second <br /> Summa canister. Duplicate groundwater samples will be collected from the same bailer or peristaltic <br /> pump into new volatile organic analysis vials. <br /> As required by DTSC, 10 percent of the total number of soil, soil gas, indoor air, and groundwater samples <br /> collected for analysis will be duplicate samples. <br /> 7.2.2 Laboratory Duplicates <br /> Laboratory duplicate samples consist of two sample aliquots collected from the same sample container <br /> and analyzed independently. Analysis of laboratory duplicate samples allows for assessment of laboratory <br /> precision of spiked analytes and other unspiked positive results. Samples will be prepared and analyzed <br /> at the rate specified in each analytical laboratories internal QA/QC procedures. <br /> 7.3 Spiked Samples <br /> Spiked samples are prepared in the laboratory to evaluate the accuracy of the analytical procedure. Three <br /> different types of spiked samples are prepared including: <br /> • Laboratory control samples <br /> • Matrix spike/matrix spike duplicate samples <br /> • Standards <br /> 7.3.1 Laboratory Control Samples <br /> A laboratory control sample (LCS) and a duplicate LCS are prepared by spiking two aliquots of a blank <br /> matrix with the target analytes for each method. Alternatively, a certified Standard Reference Material <br /> (SRM) may be extracted and analyzed as a LCS. The percent recovery and the percent difference are <br /> calculated by dividing the concentration detected by the concentration spiked and multiplying by 100. QC <br /> criteria are established for each analytical method. Samples will be prepared and analyzed at the rate <br /> specified in each analytical laboratories internal QA/QC procedures. <br /> 7.3.2 Matrix Spike/Matrix Spike Duplicate Samples <br /> Matrix spike/matrix spike duplicate (MS/MSD) samples are prepared by spiking two aliquots of a field <br /> sample with target analytes (or a subset of the target analytes). Percent recovery is calculated in the same <br /> manner as described above for LCS. MS/MSD samples are used to evaluate the accuracy of the method <br /> for the specific sample matrix. They also provide precision data for both the spike analytes and unspiked <br /> Quality Assurance/Quality Control Plan <br /> Tracy Corners Shopping Center <br /> 3225 North Tracy Boulevard <br /> Tracy,California 95376 <br /> Partner Project Number SM14-129814 <br /> Docket Number HAS-VCA 14/15-108 <br /> August 15,2016 <br /> Page 11 <br />