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GROUNDWATER SAMPLING <br /> Prior to collecting a sample of groundwater from a well, the well will be purged by <br /> removing three or more well volumes of water, using either a pump or a bailer. A well volume <br /> is defined as the amount of groundwater in the well casing and the sand pack in the annular <br /> space surrounding the casing, assuming a sand porosity of 35 percent. The pH and electrical <br /> conductivity of the water will be measured periodically during the purging. <br /> The groundwater sample will be obtained with a teflon bailer equipped with a bottom- <br /> emptying valve. To release water from the bailer with minimal aeration, the protrusion on the <br /> bottom-emptying device actuates the bottom check valve and regulates the flow into the sample <br /> bottle. <br /> The sample bottle will be obtained precleaned from the analytical laboratory, and it will be <br /> specific with respect to size and material to the type of analysis to be performed. The bottle will <br /> be carefully filled to the very top, in order to create a meniscus, and sealed with a teflon-lined <br /> cap (septa). These precautions aid in eliminating air from the sample. The sample will be <br /> visually inspected to ensure that no air bubbles remain within. <br /> Depending on the type of chemical analysis required, samples will be preserved with acid <br /> and/or they are cooled to 4 degrees Celsius. Samples then will be labeled, stored, and transported <br /> in cooled ice chests to the analytical laboratory within the permissible holding time. <br />