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at the sample site. When plastic bottles and caps are used, they will <br />be constructed of linear polyethylene. All sampling containers will <br />be used only once and discarded after analysis is complete. <br />Immediately prior to well purging, the water level and total ,depth of <br />the wells will be measured using an electric sounder. (The electric <br />sounder should be a transistorized instrument that uses a reel - <br />mounted, two -conductor, coaxial cable which connects the control panel <br />to the sensor. A low -current circuit is completed when the sensor <br />makes contact with the water, which serves as an electrolyte. The <br />current is amplified and fed into an indicator light and audible <br />buzzer, thus signaling when water has been contacted.) Water levels <br />will be recorded to the nearest 0.01 foot in the field logbook. When <br />possible, the total depth will be measured by lowering the sensor to <br />the bottom of the well. Well total depth will be recorded to the <br />nearest 0.5 foot in the field logbook for use in purge volume calcula- <br />tions. The electric sounder will be decontaminated with deionized <br />water after each use. <br />Prior to sampling, standing water in the casing and sand pack will be <br />purged from the well using either a dedicated positive displacement <br />bladder pump or a dedicated pneumatic displacement pump. The amount <br />of water purged prior to sampling will be greater than or equal to <br />four casing volumes so that water representative of the in situ ground <br />water is obtained. <br />During the purging operation, purged water will be monitored for tem- <br />perature, pH, and specific conductance at an approximate frequency of <br />one measurement per casing volume removed. Prior to collecting sam- <br />ples for laboratory analysis, these parameters must be stabilized to <br />verify that stagnant water has been evacuated from the well; that <br />PJ9 9390207.00D A-2 <br />