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where: CV = (R) (CD/2)2 (HW)(7.48) is <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 and <br />allowed to recover to 80 percent of the original well volume prior to sampling. Slow - <br />recharge wells were purged of a minimum of one well volume and also allowed to recover <br />sufficiently (for a period of no more than two hours) prior to sampling. <br />For domestic wells the water was left to run for approximately 30 minutes prior to sample <br />collection. <br />• To assess the presence of fresh water coming into the well, a Horiba U-10 Water Quality <br />Meter® (or equivalent) was used to measure electrical conductivity (EC), pH, turbidity, and <br />temperature. The water quality meter was calibrated daily with a manufacturer supplied auto - <br />calibration solution. After approximately every two to five gallons of purging, field <br />parameters were recorded on a Well Data Sheet. Sampling was performed when the total <br />estimated purge volume was reached and the EC, pH, turbidity, and temperature stabilized to <br />within 10% between consecutive readings. <br />Groundwater Sampling Using Low -Flow Purging Methods <br />Groundwater monitoring wells at the Austin Unit that are equipped with dedicated sampling <br />equipment were purged and sampled using low -flow purging methods. <br />With the weighted water -level meter in the well, the submersible pump was operated at a <br />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 EC, pH, turbidity, and temperature with the water quality meter. When three <br />consecutive readings of these field parameters had stabilized to within 10% of each other, <br />with no discernible upward or downward trend, the water quality was determined to be stable <br />and samples were collected. <br />N <br />D:\F•rwardSAplan_f06.doe <br />Geologic Associates <br />