This report presents a summary of work done on the monitoring and modeling of
acid mine drainage from the South waste rock dump at La Mine Doyon for the
period between September 1991 and December 1993. The main purpose of the
study was to measure physical and chemical properties of an actual waste dump
and to identify the key processes contributing to the generation of acid rock
drainage: hydrology, geochemistry, microbiology, and physical processes such as
oxygen, mass, and heat transfer.
Important physical parameters such as climatic data, temperature profiles within
the dump, total discharge of acid drainage from collecting ditches and chemical
composition of the effluents were monitored on a regular basis. Other parameters
were measured once or at irregular intervals: gas composition, piezometric levels,
leachate composition in the unsaturated zone, infiltration rates, particle size,
surface temperature. It is the first time that such a coherent and comprehensive set
of parameters is assembled in a large waste rock dump.
The data collected were presented in a progress report in November 1992 (Gélinas
et al. 1992) and a series of interim reports on specific topics from February 1993 to
March 1994: Guay, 1993 (procedure to enumerate iron bacteria); Choquette et al.,
1993a (rapid chemical techniques to monitor acid drainage) and 1993b (chemical
monitoring data at Mine Doyon); Lefebvre et al., 1993 (heat transfer analysis);
Locat et al., 1994 (physico-chemical and mechanical properties of waste rocks);
Choquette and Gélinas, 1994 (mineralogy and geochemical processes); Isabel et
al., 1994 (hydrology and water budget); Guay, 1994 (microbiological diversity).
Reports from Phase I of the project are also used here to present data on
monitoring installations and complete chemical analyses (including trace metals)
of selected monitoring points (Gélinas et al. 1991).
Again, this report does not present all the data available at the site but rather
integrates the information and analyses from the above sources, to present a
general synthesis of physical and chemical processes active in an acid generating
waste rock dump. We are also presenting some new information on numerical
modeling of acid mine drainage production in waste dumps.
