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P the monitoring well A low-current circuit was completed when the sensor contacted the water, which served as an electrolyte The current was 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 was decontaminated by being rinsed with deionized water after each use The bailer was lowered to a point just below the liquid level, retrieved, and observed for floating hydrocarbon Liquid measurements were recorded to the nearest 0 01 foot in the field logbook The groundwater elevation at each monitoring well was calculated by subtracting the measured depth to water from the surveyed elevation of the top of the well casing (Every attempt was made to measure depth to water for all wells on the same day.) Total well depth was then 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 was partially obstructed by silt, was recorded to the nearest 0 1 foot in the field logbook Well Purging Before sampling occurred, a bladder pump, pneumatic displacement pump, or bailer was used to purge standing water in the casing and gravel pack from the monitoring well Monitoring wells were purged according to the protocol presented in Figure A-I In most monitoring wells, the amount of water purged before sampling was greater than or equal to four casing volumes Some monitoring wells were expected to be evacuated to dryness after removing fewer than four casing volumes These low-yield monitoring wells were allowed to recharge for up to 24 hours Samples were obtained as soon as the monitoring wells recharged to a level sufficient for sample collection If insufficient water recharged after 24 hours, the monitoring well was recorded as dry for the sampling event Field measurements were recorded in a waterproof field logbook Figure A-2 shows an example of the Water Sample Field Data Sheet on which field data are recorded Field data sheets were reviewed for completeness by the sampling coordinator after the sampling event was completed The pH, specific conductance, and temperature meter were calibrated each day before field activities were begun The calibration was checked once each day to verify meter performance Field meter calibrations were recorded on the Water Sample Field Data Sheet Well Sampling A Teflon bailer or bladder pump were the only equipment acceptable for well sampling When samples for volatile organic analysis were being collected, the pump flow was regulated at approximately 100 milliliters per minute to minimize pump effluent turbulence and aeration Glass bottles of at least 40-millihters volume and fitted with Teflon-lined septa were used in sampling for volatile organics These bottles were filled completely to prevent air from remaining in the bottle A positive meniscus formed when the bottle was completely full A convex Teflon septum was placed over the positive meniscus to eliminate air After the bottle was capped, it was inverted and tapped to SAC/pj2\252U,25201000 las-94 pas 3 A-3 Rev 0 07/27/94