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-20-- <br /> CHAPTER 5 <br /> FIELD QUALITY CONTROL PROGRAM <br /> In order to establish the credibility of the sampling/analysis <br /> program, Field QC samples must be submitted along with the <br /> groundwater samples . QC sample results will have direct bearing <br /> upon well sample results and will help establish the credit- <br /> ability of the program. A good QC record can be cited to support <br /> the results submitted to the regulatory agencies . QC samples <br /> must be submitted blind to prevent possible laboratory bias . All <br /> QC samples should be made up at the well site . The contract <br /> laboratories do bench QC in addition to the above field QC. <br /> There are four types of Field QC samples: duplicates , samples, <br /> spikes , and blanks . <br /> 5 . 1 DUPLICATES <br /> Duplicates are used to monitor the variance of sampling and <br /> analysis . <br /> 5 . 1 . 1 Duplicate samples are grab samples of well water <br /> taken at the same time and under the same conditions <br /> for the same test . <br /> 5 . 1 . 2 A minimum of 100 of all samples taken should be <br /> duplicate samples. <br /> 5 . 2 FIELD STANDARDS <br /> Field standards are made up for as many analytes of interest <br /> as practical for sample spiking purposes . <br /> Preparation and use of the stock concentrate for field <br /> standards is the responsibility of the assigned Chevron <br /> Research Company (CRC) chemist . <br /> All information on preparation, use, and safety is main- <br /> tained in the Groundwater Standard Log . <br /> 5 . 3 SPIKES <br /> Spiked samples are used to measure the relative accuracy of <br /> the analysis under real conditions (varying matrix <br /> background and interferences) . <br />