MEND Report 2.22.4be
March 2000

SUMMARY

During the decommissioning of Les Terrains Aurifères (LTA-Barrick-Bousquet) site at Malartic, the preferred option for the rehabilitation of the acid-generating tailings impoundment consisted of constructing a composite cover. The cover was set up during the winter of 1995-1996 and completed in the fall of 1996. The site has been the subject of a monitoring study, within the frame of NEDEM 2000, for almost three years, with the involvement of Barrick, the Ministry of Natural Resources of Quebec and CANMET through the Canada-Quebec agreement on mineral development. A first report, concerning the construction and the instrumentation of the multi-layer cover (NEDEM 2.22.4a 1999) is available. Since that time, a new set of monitoring stations have been installed on the site in order to get a better in situ spatial representation of the present conditions, particularly in the slopes.

The present report concerns the performance of the cover during the period of 1996 to 1998. The main findings emanating from the present project are that, by capillary effect, the cover remained practically saturated over a period of three years, on the slopes as well as on top, and that the reduction of the average tailings oxidation flux was shown to be 95 % over the three years of observation.

Some zones showed local water contents lower than the design objective, particularly on the outer slopes having a significant drop in elevation. The performance observed in hydraulic break test cells indicate, however, that this type of structure would be effective in cases where supplementary intervention would be necessary in these drier zones.

Last Modified: 2003-11-26		Important Notices

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