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V Equipment Cleaning Before the sampling event starts, equipment that will be used to sample groundwater will be disassembled and cleaned with detergent water and then rinsed with deionized water. During field sampling, equipment surfaces that are placed in the well or comes into contact with groundwater during field sampling will be steam cleaned with deionized water before the next well is purged or sampled. Water Level, Floating Hydrocarbon, and Total Well Depth Measurements Before purging and sampling occurs, the depth to water, floating hydrocarbon thickness, and the total. well depth will be measured using an oil/water interface measuring system. The oil/water interface measuring system consists of a probe-that emits a continuous audible tone when immersed in a nonconductive fluid, such as oil or gasoline, and an intermittent tone when immersed in a conductive fluid, such as water. The floating hydrocarbon thickness and water level will be measured by lowering the probe into the well. Liquid levels will be recorded relative to the tone emitted at the groundwater surface. The sonic probe will be decontaminated by being rinsed with deionized water or steam cleaned after each use. A bottom-filling, clear Teflon® bailer will be used to verify floating hydrocarbon thickness measurements of less than 0.02 foot. Alternatively, an electric sounder and a bottom-filling Teflon bailer may be used to record floating hydrocarbon thickness and depth to water. The electric sounder is a transistorized instrument that uses a reel-mounted, two-conductor, coaxial cable that connects the control panel to the sensor. Cable markings are stamped at 1-foot intervals. The water level will be measured by lowering the sensor into the monitoring well. A low-current circuit will be completed when the sensor contacts the water, which serves as an electrolyte. The current will be amplified and fed into an indicator light and audible buzzer, signaling when water had been contacted. A sensitivity control compensated for highly saline or conductive water. The electric sounder will be decontaminated by being rinsed with deionized water after each use. The bailer will be lowered to a point just below the liquid level, retrieved, and observed for floating hydrocarbon. Liquid measurements will be recorded to the nearest 0.01 foot on the depth to water/floating product survey form. The groundwater elevation at each monitoring well will be calculated by subtracting the measured depth to water from the surveyed elevation of the top of the well casing. (Every attempt will be made to measure depth to water for all wells on the same day.) Total well depth will then be measured by lowering the sensor to the bottom of the well. Total well depth, used to calculate purge volumes and to determine whether the well screen is partially obstructed by silt, will be recorded to the nearest 0.1 foot on the depth to water/floating product survey form. Sac1N:\CamPklDatalArchiveWco154691ReporLs15469p101doe-95VS&I IT Corporati on B-2 02/28/00