Methodology for Monitoring Ground Water at Uranium Solution Mines

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Abstract
Monitoring the chemistry of ground water near in‐situ uranium leach mines is complicated by chemical variations unrelated to the mining operation that result from (1) spatial differences in the aquifer environment, and hence, in the water chemistry, (2) inconsistent or inadequate sampling procedures, and (3) errors in chemical analyses. Differences in the chemistry of water from place to place in the aquifer should be identified in pre‐mining baseline studies and must be taken into account during monitoring of the leaching operation, because natural waters of chemistry different from that established at a particular well during the baseline sampling period may be drawn into the monitoring well by pumping. The most important factor in developing proper sampling techniques is the configuration of the well and pumping equipment; if the pump intake is set near the point where water enters the well, and if the pumping rate is kept low to reduce turbulent mixing of waters in the well, it is not necessary to pump a full well‐bore volume before collecting a sample. Errors in chemical data can be eliminated by proper storage and handling of the samples and by careful checking of the analyses for chemical balance and eliminating the analyses that do not balance properly. Interpretation of the chemical data should be made only after assuring that these monitoring problems have been taken into account.