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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 driffing 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 p 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 using will be calculated using the following equation(s): 4-in6 welh (Total Well Depth from. the mark on the well casing (ft) - DTW (ft)) 0.653 gaYfL .3-, Prior to purging, the-water-will.be%examined-by-using-a disposable-bailer that is clear- ,enough to sex through. Features such as . *risible layers will be noted and-measured. xf immiscible layers-are observed the well will not be purged prior to sampling. _JS4- The well will then be purged using the'pu rge-pumps-:Due to the-fact that the pumps must purge waxer from depths as great as-70 to 80 feet below ground surface;pdrge rates range from 1/4 to l 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 (sec Section 4.4.6)- Dcpth to water measurements will be taken periodically during purging. The purpose of -these mea=tments is to monitor drawdown. If a de�c in groundwater elevation is mooted,the purge rate will be dccreascd until equilibrium(purge rate equals recharge rate) is achieved. The frequency of measurement will be ones every five minutes initially decreasing to once every one-half hour once equilibrium has been reached- If equilibrium cannot be reached,it will be accessary to purge the well to dryness. Purge. until less than 10°/® of the original volume of water remaim in the well. Hand bailing may be required to meet this objective, Monitor the DTW every 15 minutes to evaluate recharge. Start sample collection when either two feet of water has filled the well or.1.75 hours has elapsed since the end of pmling. Collect volatile organics no later than two hours after purging. Record all actions and measurements associated with purging a well . dry on the Purge Characterization and Sample Log. t EO-R 1\231 oR32S A•7 July 14,2404 ioM x aa,IW_