ARCHIVED REPORTS XR0001797 - Laserfiche WebLink

Home Browse Search

Water Level, Floating Hydrocarbon. and Total Well Depth Measurements Before purging and sampling occurred, the depth to water, floating hydrocarbon thickness, and the total well depth were measured using an onl/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 were measured by lowering the probe into the «ell Liquid levels were recorded relative to the tone emitted at the groundwater surface The sonic probe was decontarrunated by being rinsed with deionized water or steam cleaned after each use A bottom filling, clear Teflon'"' bailer was used to verify floating hydrocarbon thickness measurements of less than 0 02 foot Alternatively, an electric. sounder and a bottom-filling Teflon bailer may have been used to record floating hydrocarbon thickness and depth to water Tile 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 was measured by lowering the sensor into 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 atter each use The bailer was lowered to a point lust below the liquid level, ietrieved, and observed for floating hydrocarbon Liquid measurements were recorded to the nearest 0 01 foot in the Depth to Water/Floating Product Survey Form 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 deterrrune «hether the well screen was partially obstructed by silt, was recorded to the nearest 0 I foot on the Depth to Water/Floating Product Survey Form Well Purging Before sampling occurred, a polyvinyl chloride (PVC) bailer, centrifugal pump, low-flow submersible pump, or Teflon bailer was used to purge standing water in the casing and gravel pack from the monitoring well Monitonng %Nells were purged according to the protocol presented in Figure A-1 In most monitoring N, ells, the amount of water purged before sampling was greater than or equal to three casing volumes Some monitoring wells were expected to be evacuated to dryness after removing fewer than three 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 "as recorded as dry for the sampling event I