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7.1 Blank Samples The analytical results of blank samples are used to assess the potential for contaminants to be introduced into the samples during container manufacture, container handling in the field, during shipment, or in the laboratory. 7.1.1 Equipment Blanks An equipment blank is prepared by exposing sampling groundwater containers or sample collection devices to the sampling environment without allowing them to mix with the matrix of interest. Equipment blanks will be collected after decontamination of the sampling devices by rinsing the collection device that would normally contact the sample with deionized water. Results obtained from the analysis of equipment blank samples are used to assess potential contamination from sample collection devices and ambient Site conditions. Other potential sources of contamination may include laboratory reagents, sample container and laboratory glassware cleaning procedures, and/or contact with analytical glassware or other apparatus during laboratory sample preparation and analysis. One equipment blank will be collected each day during which groundwater samples are collected. 7.1.2 Field Blanks Field blanks are aliquots of the deionized water used to collect the equipment blanks but are not exposed to the sample collection equipment. If an equipment blank analysis indicates the presence of contamination, the field blank analysis can be used to isolate the source of the contamination. A field blank should be collected each time an equipment blank is collected, or when a new source of water is used. One field blank will be collected each day during which groundwater samples are collected. 7.1.3 Laboratory Blanks Laboratory blanks are prepared in the analytical laboratory each day that samples are extracted, and are indicative of contamination that is derived from laboratory procedures. The rate of laboratory blank sample preparation and analysis per field sample extracted is specified in each analytical laboratories own internal QA/QC procedures. 7.2 Trip Blanks and Duplicate Samples Trip blanks can be used to identify systematic sources of cross-contamination and will be provided by the analytical laboratory. The trip blank containers, which will be filled with deionized water, will be stored in the iced cooler for the duration of the sampling episode and submitted to the laboratory for analysis along with the collected samples. Each cooler containing samples to be analyzed for TPH-GRO or VOCs will include one trip blank sample. Duplicate samples are separate samples collected from the same location at the same point in time. The analytical results obtained from these samples are used to assess the precision of sampling and analysis. There are several different types of duplicate samples that may be prepared. Quality Assurance/Quality Control Plan Tracy Corners Shopping Center 3225 North Tracy Boulevard Tracy,California 95376 Partner Project Number SM14-129814 Docket Number HAS-VCA 14/15-108 August 15,2016 Page 10