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i 1 Sample Collection Sample collection procedures include equipment cleaning, water-level and total well-depth measurements, and well purging and sampling Equipment Cleaning g Before the sampling event is started, equipment that will be placed in the well or will come in contact with ground water will be disassembled and cleaned thoroughly with detergent water, and then steam cleaned with deionized water During field sampling, equipment surfaces that are placed in the well or contact ground water will be steam cleaned with deionized water before the next well is purged or sampled Water-level, Floating Hydrocarbon, and Total Well-depth Measure- ments Before purging and sampling occurs, the depth to water, floating hydro- carbon 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 emus a continuous audible tone when immersed in a nonconductive fluid, such as oil or gasoline, and an inter- mittent tone when immersed in a conductive fluid, such as water Liquid levels will be recorded relative to the tone emitted at the ground-water surface The probe will be decontaminated by rinsing with a nonphosphate detergent solution and then double rinsing with deionized water or steam cleaning after each use Alternatively, an electric sounder and a bottom- filling, clear 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 monitonng well A low-current circuit is completed when the sensor contacts the water, which ' serves as an electrolyte The current is amplified and fed into an indicator light and audible buzzer, signaling when water has been contacted A sensitivity control compensates for highly saline or conductive water The ' electric sounder will be decontaminated by rinsing with a nonphosphate detergent solution and then double rinsing with deionized water after each PRA P91 K022 A0W Rev 0 February 7, 1992