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A method is proposed to verify whether wells and piezometers have been adequately sealed into the ground to avoid vertical communication between aquifers and thus prevent misleading results of both piezometric levels and contamination degrees. The method makes use of variable-head permeability tests that are not interpreted by the common graph of ln H versus t, but by the more fundamental graph of the water velocity versus the total head difference. Both presentations are mathematically equivalent. If there is some error in the “measured” piezometric level, it will be hidden in the common logarithmic diagram, but it can be easily detected with the proposed velocity diagram. The method is illustrated by typical examples of velocity diagrams and their interpretation. According to the author's experience, the practice of partial seals along piezometer pipes should be discouraged and a full-length seal is preferred.
ground water, piezometer, well, water level, contamination, permeability, reliability, proving method, evaluation
Research scientist, Ecole Polytechnique de Montréal, Sta.A, Montréal, Québec