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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 1 be checked two to three 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 adpsted accordingly, Example calibration logs are included in.Appeudhc'C. During purging and sampling of the was the instruments will be used in the same manner as during calitnation, 2. Depth to water will be mustered again,prior to saamft- in each well as described in Section 4.4.1 and recorded on the Purge C haracterizatiort and Sample Log. The volume %of groundwater in the well casing will be calculatedcuing the following 4--inch 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 wilt-be-.c ned by-using- disposable:bailer that is clear- -enough to see through. Features such as humiscz'bie layers will be noted and measured_ ^If'i nmisci'ble layers-are observed the well will not be purged prior to sampling. 4- The well will then be ed using the-purge Due to the-fact that the prates I -` PmS $ Pm$ PCPs- must Purge water from depths as great as 70 to 80 feet below ground surfic;c,purge rates range from 1/4 to I gallon per minute_ ?his-purge rate does not appear to exceed the recharge k rates. of the wells. Purge water will be discharged to-the ground (see Suction 4.4.6)_ Depth to water measurcfinenu will be taken periodically during pig The Pmpose of these measurements is to monitor dxaw+down. If a decrcasa in groom elevation is .sroted,the purge rate will be d=i-_mqd until vimilibrium(purge rata equals recharge rate) _ is achieved. The frequency of measurement will be-once every five minutes iruitially dig to once every one4mWhour once equilibrium has beta reached. If equilibicrvm cannot be ruched,it will be necessary to purge the well to dryness_ Purge. Ura less than 104/o of the original volume of water_nmains in the well. .Hamid bailing may be required to meet this objective. Monitor the DTW every 15 minutes to evaluate r6charge. Start sample collation when wither two feet of water has filled the well or 1.75 hours has elapsed since the end of Purging. COUea vola#dc Organics no later than two hours alter purging. Record all actions and measurements associated with purging a well dry on the purge Characterization and Sample Log. a49-F011Z310It323 A-7 My 14,2000 20401Crclafe�dsr.lac.