ARCHIVED REPORTS XR0006868 - Laserfiche WebLink

Home Browse Search

Water-level, Floating Hydrocarbon, and Total Well-depth ' Measurements 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 sonic 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 low- ering the sonic probe into the well. Liquid levels will be recorded relative to the tone emitted at the ground-water surface. The sonic probe will be ' decontaminated by being rinsed with deionized water after each use. Alternately, 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 monitoring 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 being rinsed with deionized water after each use. The baiier 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 in the field ' logbook. The ground-water elevation at each monitoring well will be cal- culated by subtracting the measured depth to water from the surveyed elevation of the top of the well casing. (Every attempt will be made to mea- sure 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 0.5 foot in the field logbook. ' PMt92V920201 a C - 3 Rev. 0 June 1, 1992