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0 <br /> CV=(II)(CD/2)2 ( )(7.48) <br /> where: <br /> CV = casing volume(gallons) <br /> CD = casing diameter(feet) <br /> HW = height of water column within well(feet) <br /> 7.48 = conversion from cubic feet to gallons. <br /> • Each well with sufficient recharge was purged of a minimum of three casing volumes <br /> and allowed to recover to 80 percent of the original well volume prior to sampling. <br /> Slow-recharge wells were purged of a minimum of one well volume and also allowed <br /> to recover sufficiently(for a period of no more than two hours)prior to sampling. <br /> • To assess the presence of fresh water coming into the well, dissolved oxygen (DO), <br /> electrical conductivity(EC),pH,turbidity, and temperature were monitored after <br /> approximately every two to five gallons of purging and were recorded on a Well Data <br /> Sheet. Sampling was performed when the total estimated purge volume was reached <br /> and the EC,pH, turbidity, and temperature stabilized to within 10%between <br /> consecutive readings. <br /> • Where a bailer was used for sample collection, a bottom-emptying device was <br /> inserted into the bailer, and the sample was transferred from the bailer to the <br /> container at a rate so as to minimize aeration. <br /> Groundwater Sampling Using Low-Flow Purging Methods <br /> • Groundwater monitoring wells that are equipped with dedicated sampling equipment <br /> were purged and sampled using low-flow purging methods. <br /> • With the weighted water-level meter in the well, the submersible pump was operated <br /> at a discharge rate that would minimize the decline in water level. <br /> • Discharged water was routed through a sampling chamber equipped with probes for <br /> measuring DO, EC,pH, turbidity, and temperature. When three consecutive readings <br /> of these field parameters had stabilized to within 10% of each other, the water quality <br /> was determined to be stable and samples were collected. <br /> Groundwater Sampling Collection and Preparation <br /> • Samples, including field, trip, and equipment blanks, were collected in approved <br /> sample containers (Table 1), and each container was filled completely and <br /> immediately capped, labeled, and placed in a cooler with ice. Samples for VOC <br /> analysis were filled by pouring the sample down the side of the container to minimize <br /> aeration and capped with no airspace. <br /> 2 Geo-Logic Associates <br />