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Quality Assurance/Quality Control Plan Page 11 <br />12.0 GROUNDWATER SAMPLING PROTOCOL <br />Prior to arriving at the sampling site, all sampling equipment will be washed with laboratory <br />grade detergent, and rinsed twice with tap water, once with acetone, and once with deionized <br />water. This procedure will be carried out on-site before sampling of other monitoring wells, <br />if more than one well is to be sampled with the same sampling device. <br />Immediately prior to sampling, the depth to water (DTW) in the well will be recorded. The <br />thickness of free phase LNAPL on top of the groundwater, if present, will be measured using <br />an interface probe. The procedure for monitoring is presented in Section 9.0 (Groundwater <br />Monitoring Protocol). <br />If free LNAPL is detected, analysis of groundwater at the interface for dissolved product will <br />not be conducted. A product sample will be collected for source identification, as needed. If <br />free product cannot be removed, an interval specific sampling device may be utilized to collect <br />a sample from below the zone of free product. Before collecting groundwater samples from <br />a well, the well will be purged until indicator parameters (temperature, conductivity and pH) <br />stabilize. This will entail the removal of at least four well casing volumes by bailing or <br />pumping. The criteria for determining well casing volumes and temporary storage of purged <br />water is outlined in Section 10.0, (Well Development Protocol). The indicator parameter <br />measurements will be taken both before and after purging of each well casing volume. Once <br />the well is purged and indicator parameters have stabilized, a sample will be collected after the <br />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 <br />sample containers. <br />Cross contamination from transferring pumps (or bailers) from well to well will be avoided by <br />utilizing dedicated equipment. Were this is not feasible, thorough cleaning of equipment will <br />be performed between sampling rounds. Sampling will proceed from the least contaminated to <br />the most contaminated well, if information is available before sample collection, or if it is <br />