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1. The pH, conductivity, and turbidity meters will be calibrated at a minimum at the be of each sampling day using commercially obtained-standards. Calibration will be checked two to thrix times during the day to evaluate the potential that the calibration is drifting throughout the day. -If instrument drift is detected in the field, the measurements taken during purging and sampling will be adjusted accordingly Example calibration Iogs we included in Appen ® •C.. During purging and sampling of the wells the instruments will be used in the same manner as arming calibration. 2. Depth to water will be measured agam, prior to sampling, in each well as described in Section 4.4.1 and recorded on the Purge Characterization,and Sample Log. The voIcrme of groundwater in the well casing will be calculated using the following egnation(s): 4-inch well- '(Total Well Depth from the mark on the well casing (ft) - DTW (fc}) x 0-653 gal/ft. 3_ Prior to purging, the-water,wilt be-. ' ed-by using-a disposable:barer that is clear- ,enough to sec through- Features such as immiscible layers will be noted and-measured. If'unmzsct'ble layers-are observed the well will not be purged prior to sampling_ _. 4- The well will then be purged using the-purge s;Due to the-fact that the pumps must PBS water from depths as grant as 70 26 80 feel below ground surface,purge rates range from 1/4 to I gallon per minute. Tbis-purgc rate docs not appear to exceed the recharge rates. of the wells. Purge water will be discimrged to-the ground (ser Section 4.4.6)- Depth to water m inerts will be taken periodically during Pte& The purpose of these measurements is to monitor-drawdown- If a decrease in grouudwatcr elevation is noted,the purge rate will be deczeased until equilibrium(purge rate equals recharge rate) _ is achieved. The hequency of measurement will be-once every five minutes initially -to once every one-halfhour once en equilibrium has bereachecL drag If equilibrium cannot be reached;it will be necessary to purge the well to dryness_ Purge. - until less than l(T'/a of the original volume of water ins in the well. Hand bailing may be requhvd to meet this objective. Monitor the DTW every 15 minutes to evaluate recharge. Start sample collection when citha two feet of water has filled the well or 1.75 - hours has elapsed since the cad of purging. Collect volare organics no later than two heeirs after purging. Record all actions and measurements associated with purging a well dry on the purge Characterization and Sample Log. 23-4831149-R tt2310R325 A-7 July 14,2400 Copyrkhc 2000 KkkAUkr.ter-