The environmental risk assessment presented to the community of Oujé-Bougoumou March 31 is a wide-ranging overview of data collected from the region’s soils, water and sediments, as well as fish, birds and mammals. The “Screening Level Environmental Risk Assessment,” or SLERA, is not meant to assess risk to human health, but rather is a survey of many studies conducted over the last several years, and some from decades ago.
The review was conducted by environmental research firms RISCAN and Alliance Environnement Inc., with Denis Laliberté of the Quebec Environment Ministry as Project Manager. Riscan biologist Jacques Bérubé served as the Project Director.
The SLERA identifies three sites as presenting major impacts: the Barette-Chapais sawmill, the Opémiska mine, and the Joe Mann Mine. Sites of concern include the Corner Bay Mine Property and a former mining site on the backs of Lake Roberge. Other mining sites the study authors deem to pose a “minor” threat. Further concerns identified by the study include 19 illegal waste-deposit sites near Chapais and Chibougamau.
The Joe Mann Mine, about 65 km south of Chibougamau, began operation in 1950. As the study observes, untreated mine tailings containing mercury were long dumped in the Nemenjiche River, and the mine’s current mining effluent continues to be discharged year round, untreated, into the Nemenjiche.
The Principale Mine on Île Merrill in Lake Aux Dorés, now closed, discharged cyanide used to extract gold from mined ore into the lake. The study says restoration work attempted in 1989-90 is insufficient, and that the effluent from the Principale mine has a “significant effect” on invertebrates, which are consumed by lake fish in contaminated areas.
Three heavy metals measured in Lake Aux Dorés – arsenic, copper and nickel – often exceeded thresholds for adverse biological effects. Concentrations were up to 2.3 times the threshold for nickel, 15 times the limit for arsenic and 40 times the threshold for copper. These concentrations were found in the sediments near the mining activities of the Copper Rand and Principale mines, and abnormally high readings were found up to 3.5 km downstream from the tailings sites.
In Lake Chibougamau, meanwhile, thresholds for arsenic, copper, nickel, cadmium and chromium were exceeded at many test sites. Sites containing spawning grounds considered essential to the survival of Lake Trout populations showed readings of arsenic, copper, nickel and cadmium that exceeded thresholds. Low breeding rates for Lake Trout in Lake Chibougamau were observed in a variety of studies that were reviewed by the SLERA, with some researchers raising concerns that these low rates could be explained by the high metal contamination levels of spawning grounds.
Downstream from the Joe Mann Mine, the Nemenjiche River produced samples with readings 37 to 44 times the limit for arsenic, 19 to 27.5 times for copper and 7.9 to 11.7 times for mercury.
Studies of fish caught in Lake Aux Dorés showed concentrations above the detection limit for copper, iron, cyanide, manganese, mercury, strontium and zinc. In Lake Chibougamau, fish samples produced readings above the limit for copper, manganese, mercury, selenium, strontium and zinc.
The SLERA concludes that risk to aquatic life from mining effluent impacts on water quality are posed by the Joe Mann, Principale and Copper Rand mines, with the highest risks on the Nemenjiche River and the Lake Aux Dorés. Metal concentrations in sediments sufficient to cause risk are also in the Nemenjiche River, and in the Obatogamau Lakes, Lake Chibougamau and Lake Aux Dorés. This risk is blamed on mine tailings that “escaped” from tailings sites in the past.
Birds and mammals that feed on fish are considered at risk from levels of mercury and selenium high enough to cause risk in the affected areas. For example, mammals feeding on fish from Lake Chibougamau are at risk of selenium contamination.
Birds and mammals could also be affected by the metal concentrations in invertebrates that are a food source for fish. Thus, several layers of the food chain can be affected by manganese and barium found in collected samples. Again, these risks are concentrated in Lake Chibougamau and Lake Aux Dorés, though other areas, the authors note, cannot be excluded because there is not enough data from which to make a judgment.
A surprising conclusion the SLERA authors make is that mining activities are not to blame for the low breeding rates of Lake Trout in Lake Chibougamau, despite the high contamination levels found in spawning grounds there. They note that other spawning grounds with similar readings for metals produce higher breeding rates in concluding that mining contamination must not be a factor.
Overall, the authors do say that many of the risks identified can be linked to mining activities. “This is not surprising given that mining is one of the most important industries in the region and that over the last 50 years it has produced large quantities of tailings enriched in several metals,” the SLERA observes.
They identify a bias in the studies reviewed toward mining activities but acknowledge that “it must be admitted that this bias has merit since no other important industry in the region has been identified as a major source of contaminants.” Indeed, the concentration of metals in Lake Chibougamau and Lake Aux Dorés “is essentially permanent and can easily be many years old,” they write.
These areas are targeted for highest priority in their recommendations, especially areas closest to mining activities. They recommend herbivore data collection from at-risk areas on the shores of Lake Aux Dorés and Lake Chibougamau, testing for aluminium, manganese, mercury, arsenic and copper. Similar testing of sediments and benthic fauna (small aquatic invertebrates on which fish feed) in these areas is also recommended. Other recommendations suggest water testing and food fish monitoring.
Ultimately, the authors conclude that the costs of effective remediation efforts would be prohibitive.
“Risks are associated with parts of these aquatic systems that have been affected by the mining activities that have taken place in the region over the last 50 years,” they write. “The areas at risk are potentially extensive, and may cover, at varying degrees of risk, a substantial fraction of the bottom areas of these bodies of water. It is unrealistic to expect the complete remediation of such large areas since the costs and environmental impacts of such an endeavour would quickly become limiting.”
Instead, they recommend remediation efforts in specific, more extensively tested sites, and to limit future damage by controlling or limiting sources of contamination.
