A Novel Approach to Assessing the Cause of Impacts on Benthic Macroinvertebrate Communities, and Distinguishing Between Sediment Vs Waterborne Effects Downstream of a Metal Mining Discharge

Hudbay has owned and operated a base metal mine and metallurgical complex in the
Flin Flon area of northwestern Manitoba for over 90 years. Zinc and copper ores are
processed from local mines and concentrates from external sources. The Flin Flon
tailings impoundment system (FFTIS) receives input from several processes, such as
mill effluent waste, dewatering from underground workings, surface runoff and storm
water drainage, and runoff from the town of Creighton. FFTIS effluent is discharged into
Flin Flon Creek, where it comprises approximately 70% of the creek volume. The
effluent concentration decreases as it flows into the Northwest Arm of Schist Lake,
where it is approximately 30%.
Benthic invertebrate community surveys downstream of the FFTIS have shown that
benthic invertebrate communities in Flin Flon Creek are severely impacted and
dominated by a single pollution-tolerant species: the midge larva Chironomus (Stantec
2005, 2007, 2009, 2011). In the NW Arm of Schist Lake, benthic communities are also
impacted but not to the same extent.