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total well-depth measurements, and well purging and'sampiing. <br /> Equipment Cleaning <br /> Before the sampling event-is started, equipment that will be placed in the;: ; <br /> well or will come in contact with ground water will be disassembled and <br /> cleaned thoroughly with detergent water, and then steam cleaned with <br /> deionized water. During field sampling, equipment surfaces that are <br /> placed in the well or contact ground water will be steam cleaned with <br /> deionized water before the next well is purged or sampled. <br /> Water-level, Floating Hydrocarbon, and Total Well-depth Measure- <br /> ments <br /> Before purging and sampling occurs, the depth to water, floating hydro- <br /> carbon thickness, and the total well depth will be- measured using an <br /> 0 oil/water interface measuring system. The oil/water interface measuring <br /> system consists of a probe that emits a continuous audible tone when <br /> immersed in a nonconductive fluid, such as oil or gasoline, and an inter- <br /> mittent tone when immersed in a conductive fluid, such as water. Liquid. <br /> levels will be recorded relative to the tone emitted at the ground-water. <br />• ! surface. The probe will be decontaminated by rinsing with a nonphosphate <br /> detergent solution and then double rinsing with deionized water or steam <br /> cleaning after each use. An electric sounder and a bottom-filling, clear <br /> Teflon® bailer will be used to record floating hydrocarbon thickness and <br /> depth to water if product thickness less than 0.02' is detected. <br /> The electric sounder is a transistorized instrument that uses a reel- <br /> mounted, two-conductor, coaxial cable that connects the control panel to <br /> the sensor. Cable markings are stamped at 1 foot intervals. The water <br /> level will be measured by lowering the sensor into the monitoring well. A <br />• low-current circuit is completed when the sensor contacts the water, which <br /> serves as an electrolyte. The current is amplified and fed into an indicator <br /> light and audible buzzer, signaling when water has been contacted. A <br /> sensitivity control compensates for highly saline or conductive water. The <br /> electric sounder will be decontaminated by rinsing with a nonphosphate <br />• detergent solution and then double rinsing with deionized water after each <br /> use. The bailer will be lowered to a point just below the liquid level, <br /> retrieved, and observed for floating hydrocarbon. <br /> Liquid measurements will be recorded to the nearest 0.01 foot in the field <br /> PRO P91 L028.DOC Rev. 0 February 6, 1992 <br />