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r <br /> Quality Assurance/Quality Control Plan Page 11 <br /> • <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 carred 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 to Section 9.0 (Groundwater <br /> Monitoring Protocol) <br /> If free LNAPL 1s 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 transfemng 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 />