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connects the control panel to the sensor. Cable markings are stamped at 1-foot <br /> increments. The water level is measured by lowering the sensor into the monitoring well. <br /> A low-current circuit is completed when the sensor contacts the water, which serves as an <br /> electrolyte. The current is amplified and fed into an indicator light and audible buzzer, <br /> signaling when water has been contacted. A sensitivity control compensates for highly <br /> saline or conductive water. The electric sounder is decontaminated by rinsing with <br /> deionized water after each use. <br /> Depth to water is recorded to the nearest 0.01 foot in the field logbook. The groundwater <br /> elevation at each monitoring well is calculated by subtracting the measured depth to <br /> water from the surveyed elevation of the top of the well casing. The total depth of the <br /> well is then measured in the monitoring wells scheduled for sampling by lowering the <br /> sensor to the bottom of the well. The total depth of the well, used to calculate purge <br /> volumes and to determine whether the well screen is partially obstructed by silt, is <br /> recorded to the nearest 0.1 foot in the field logbook. <br /> Sample Collection <br /> Sample collection procedures include equipment cleaning, water level and total well <br /> depth measurements, well purging and sampling, surface water sampling, leachate <br /> sampling, and lysimeter sampling. <br /> Equipment Cleaning <br /> All sample containers are provided by the laboratory and prepared with preservatives as <br /> needed. <br /> During field sampling, equipment surfaces that are placed in the well or contact <br /> groundwater are decontaminated using a steam cleaner and deionized water before the <br /> next well is purged or sampled. <br /> Water Level and Total Well Depth Measurements <br /> Immediately before a monitoring well is purged, the water level and total well depth are <br /> measured using an electric sounder as described in the previous section "Groundwater <br /> Elevation Survey." The electric sounder is decontaminated by rinsing with deionized <br /> water after each use. <br /> Well Purging <br /> Before sampling occurs, standing water in the casing and gravel pack are purged from the <br /> monitoring well using a dedicated submersible pump. In most monitoring wells, the <br /> amount of water purged before sampling is equal to or greater than three casing volumes. <br /> Foothill WQPS Rev Ldoc <br /> A-2 <br />