ISSN: 0149-6115
Published Online: 12 July 2006
Page Count: 8

Detecting and Quantifying Leakage Through Defective Borehole Seals: A New Methodology and Laboratory Verification

Chesnaux, R
Simon Fraser University,BC,
Geological and Mining Engineering, Ecole Polytechnique de Montreal,QC,

Chapuis, RP
Geological and Mining Engineering, Ecole Polytechnique de Montreal,QC,

(Received 22 February 2006; accepted 19 June 2006)

Abstract

A new method for quantifying leakage through poorly sealed boreholes is presented and verified using a laboratory scale sandbox experiment. The method applies to a leaky borehole between two aquifers separated by an aquitard. A nonreactive tracer is injected into an upper aquifer piezometer, and the lower aquifer is pumped at a fixed rate. First, the presence of the tracer in the recovered water indicates the existence of the hydraulic short-circuit and cross-contamination. The leakage rate associated with the pumping rate can then be determined by measurement of the recovered tracer concentration. By correlating the leakage rate with the pumping rate, the hydraulic properties of the defective seal can be determined and the degree of cross-contamination can be predicted for any pumping rate. The method will be useful for practitioners who need to evaluate the quality of a borehole seal. The method is successfully tested using a laboratory sandbox experiment.

Keywords:
groundwater protection, laboratory experiments, aquitard, confined aquifer, hydraulic short-circuit, cross-contamination, tracer tests

Paper ID: GTJ100500
DOI: 10.1520/GTJ100500
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