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ATC Associates Inc. <br /> Quality Assurance/Quality Control Plan <br /> Revised February 1995 <br /> deionized water. this procedure will be carried out on-site before sampling of other monitoring wells, if <br /> more than one well is to be sampled with the sample sampling device. <br /> Immediately prior to sampling, the depth to water(DTW) in the well will be recorded. The thickness <br /> of product on top of the groundwater, if present, will be measured using an interface probe. The <br /> procedure for monitoring is presented in Section 9.0 (GrotmdwaterMonitoringProtocol). <br /> If free product is detected, analysis of groundwater at the interface for dissolved product will not be <br /> conducted. A product sample will be collected for source identification. If all free product cannot be <br /> removed, an interval specific sampling device may be utilized to collect a sample from below the zone <br /> of free product. Before collecting groundwater samples from each well, the well will be purged until <br /> indicator parameters (temperature, conductivity, and pH) stabilize. This will entail the removal of at <br /> least four well casing volumes by bailing or pumping. The criteria for determining well casing volumes <br /> and temporary storage of purged water is outlined in Section 10.0 (Well Development Protocol). The <br /> indicator parameter measurements will be taken both before and after purging of each well casing <br /> volumes. Once the well is purged and indicator parameters have stabilized, a sample will be collected <br /> after the water level approaches 80 percent of its initial elevation. Where water level recovery is slow, <br /> the sample will be collected after stabilization is achieved and enough water is present to fill sample <br /> containers. <br /> Cross contamination from transferring pumps (or bailers) from well to well will be avoided by utilizing <br /> dedicated equipment. Where this is not feasible, thorough cleaning of equipment will be performed <br /> between sampling rounds. Sampling will proceed from the least contaminated to the most <br /> contaminated well, if information is available before sample collection, or if it is indicated by field <br /> W:\Adnun\Shells\QAQC-98.D0C <br /> 13 <br />