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Steel Tape <br />To obtain a water level measurement using a steel tape, one needs to remove the <br />top cap of a well, disinfect the portion of the tape being lowered into the well, <br />chalk up the end portion of the tape expected to come in contact with the water <br />surface, lower the tape and record the depth to which the tape is extended, then <br />raise the tape using a hand crank and record the mark which identifies the <br />division between wet and dry chalk, and finally subtract the two measurements. <br />Pros: Can be used with very small opening in the well head. <br />Cons: Time intensive process to deploy and retrieve the tape; may require <br />multiple attempts depending on estimate of water level; difficult to read clearly <br />due to well condensation; requires disinfection of tape; limited to length of steel <br />tape (State's steel tape is 500 feet). <br />M-scope <br />To obtain a water level measurement using an M-scope one needs to open the <br />well to allow for a well measurement, disinfect the conductivity probe, and lower <br />the conductivity probe into the well until a voltage meter indicates that water has <br />been encountered. A water level is recorded by reading the amount of wire <br />attached to the probe at a specified measuring point when the circuit is <br />completed. <br />Pros: Provides clear indication of water level. <br />Cons: Many wells do not have large enough access ports for probe; lowering the <br />probe into the well can cause it to get tangled with electrical wires in well (as <br />occurred several times during Task 39.1); time intensive process to deploy and <br />retrieve in deep wells; may require two people to operate in deep well; requires <br />disinfection; limited to depth of cable attached to the probe (State's M-scope is <br />1,000 feet). <br />Airline <br />To obtain a water level measurement using an airline, one needs to have a <br />nitrogen tank, regulator, pressure gages and tube fittings. A tube leaving the <br />regulator is connected to the airline at the well. The airline is filled with nitrogen <br />gas and all the water is purged out of the airline. When the pressure in the airline <br />comes to equilibrium with the water level in the well a pressure level is noted. <br />This pressure is then converted into a depth to water level using the airline <br />depth. <br />Pros: Is anon-obtrusive method to measure water level; may be the only <br />available method to measure water level in well. <br />Cons: Requires nitrogen tank, gages and fittings; requires accurate airline depth; <br />airlines may have leaks; time intensive to set up connections; the accuracy of the <br />