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1• The pH, conductivity, and turbidity meters will be calibrated at a minimum at the beginning of each sampling day using commercially obtained.standards. Calibration will be checked two to three times during the day to evaluate the potential that the calibration is dff&g throughout the day. -If instrument drift is detected in the field, the measurements taken during purging and sampling will be adjusted accordingly. Example calibration logs are included in Appendix-C. During purging and sampling of the wells the instruments will be used in the same manner as during calibration. 2. Depth to water will be measured again, prior to sampling, in each well as described in Section 4.4.1 and recorded on the Purge Characterization and Sample Log. The volume of groundwater in the well casing will be calculated using the following equation(s): flinch well: _(Total Well Depth from the mark on the well casing (ft) - DTW (ft)) x 0.653 gal/fL 3.' Prior to purging, the-water•will.be-. ' ed-by-using-a.disposable'bailer that is clear enough to see through. Features such as immiscible layers will be noted and-measured- pIf immiscible layers-are observed the well wiH not be purged prior to sampling- -- 4. The well w�71 then be ed using the a s._Due to the-fact that the pumps must { P'i'g 8 PSK PSP Purge water from depths as great as-70 to 80 feet below ground surfac.,purcge rates range from 1/4 to 1 gallon per minute. This purge rate does not appear to exceed the recharge rates. of the wells, Purge water will be discharged to-the ground (see Section 4.4.6). Dtpth to water measurements: will be taken periodically dudng purging. The purpose of these measurements is to monitor drawdown.. If a decrease in groundwater elevation is the purge rate will be decreased until equilibrium(purge rate equals recharge rate) is achieved. The fivquency of measurement will be-once every five minutes initially decreasing to once every one-half hour once equilibrium has been reached. If equilibrium cannot be reached,it will be necessary to purge the well to dryness. Purge. until less than 10'o of the original volume of water re.mams in the well Hand bailing Pay be required to meet this objective. Monitor the DTW every 15 minutes to evaluate rex e. Start sample collection when either two fret of water has filled the well or.1.75 hours has since the end of p . Collect tioMe organics no later than two hours after Purging. Record all actions and measurements associated with purging a well dry on the PurZe Characterization and Sample Log. y 234U E4 11231 OR325 A•7 lnly 14,2000 der.rac.