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where: CV=(n)(CD/2)2 (HW)(7.48) <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 /> Checker®was used to measure electrical conductivity(EC),pH, turbidity, and temperature. <br /> The Horiba U-10 Water Quality Checker®was calibrated daily with a manufacturer supplied <br /> auto-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 Horiba U-10 Water Quality Checker®. <br /> When three consecutive readings of these field parameters had stabilized to within 10%of <br /> each other,with no discernible upward or downward trend, the water quality was determined <br /> to be stable and samples were collected. <br /> • <br /> 2 <br /> DAForwardSAplan w06.doc <br /> Geologic Associates <br />