The Fermont waste water treatment plant discharges through lakes Daviault and Sans-Nom into Carheil Lake, in the Moisie River watershed. In April 2011 it was reported that water management experts in Sept-Îles were concerned about cyanobacteria, or blue-green algae, that had been found in Carheil Lake and had potential to further affect the Moisie River. The bloom was due to phosphorus discharge from the treatment plant, which has since been reduced.
Fermont is in an area of rounded hills and flat areas with peat bogs, wetlands and many lakes and small streams. The valleys show the influence of glacial action and contain undifferentiated glacial till and fluvioglacial deposits of sand and gravel. Lake Perchard, to the north of Fermont, supplies the town with drinking water.