The GREGI research team has conducted, since 1992, a large amount of characterization and research work on the site of the South waste rock dump at La Mine Doyon, Quebec. This is part of a larger research program going on at this site since 1990 and aimed at the understanding and the solving of acid mine drainage problems associated with waste rock piles. This research program is part of the MEND national program and is funded by La Mine Doyon (owned by Lac Minerals and Cambior), by the Quebec provincial government through CRM and by the federal government through CANMET. This report is submitted to CANMET as required in the funding agreement.

Acid mine drainage (AMD) generation from waste rock dumps (WRD) constitute a challenging problem for the mineral industry of Canada. Unlike AMD generated by tailings ponds, AMD generated by WRD are more concentrated and can reach much higher flow rates. So, even if acid generating WRD are less common than acid generating tailings ponds, they constitute an important threat to the environment and must be managed at great cost by the mineral industry.

La Mine Doyon South waste rock dump is one of the largest acid generating dump in Eastern Canada. Since the beginning of this research program, numerous reports describing the site and the ongoing physico-chemical processes had been released by GREGI. It is now well established that the large magnitude of the AMD production at the WRD is related to the rapid supply of air and water to the reaction sites through convection and percolation in this very permeable porous medium.

Water entering a dump from precipitation is a key element in the AMD generation processes and is the main vector of acid release into the environment. This is why a complete characterization of the AMD processes in a waste rock dump must include a comprehensive water budget.

The first objective of this report is to present the hydrologic data made available by the various characterization programs going on at La Mine Doyon. This data is growing as monitoring continues and as new monitoring devices are regularly added. This report presents a preliminary analysis of a developing body of data and knowledge about hydrologic processes at La Mine Doyon South dump.

The measurement of hydrologic variables like rainfall, temperature and drainage flow rates is straightforward. But other key hydrologic variables, like infiltration, are more difficult to measure and some development of monitoring procedure or devices are included in the project. Automation of monitoring devices is also used to ease the task of on-site data collection and ensure a more continuous record of key data. The second objective of this report is to present both classical and innovative methodologies for monitoring hydrological processes at La Mine Doyon site.

The third and final objective of this report is to present a comprehensive water budget of the South dump. This budget must be consistent with observations provided by the geochemical and mineralogical data available. This type of information was used to build a geochemical mass budget related to the water budget through concentration and volume changes.

As stated earlier, classical hydrological methods were used when applicable. These include analysis of meteorological and climatic data from close by weather stations as well as the operation of an automatic weather station on the site. Weir stations and piezometers are also operated on the site. Some less standard instrumentation used in this project include lysimeters stations.

The methodology is thus straightforward. We try to measure as many hydrological variables as possible to obtain the longest and most accurate records as possible. This data is used to build the water budget. As the project has been going on for more than 4 years, some records are becoming more and more significant. Moreover, as the water budget picture becomes clearer, data deficiencies are identified and new monitoring devices are designed and put into operation.

The analysis of hydrological data collected is also supported with some modeling. Models are used to assess hydrologic variables that cannot be measured. Model calibration with measured data ensures genuine modeling estimations.

Last Modified: 2003-11-26		Important Notices

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