Vale Base Metals has operated the Long Harbour Processing Plant (LHPP) since 2014. The hydrometallurgical process facility includes a concentrate re-grind circuit, pressure oxidation autoclaves, neutralization and impurity removal circuits, and electrowinning to recover nickel, cobalt, and copper metals. Waste streams from the various processing stages are neutralized with residues deposited into a subaqueous storage area near the plant site. The plant was designed to process low-arsenic content Voisey’s Bay sourced nickel concentrate (<0.001% As). In 2016, nickel concentrate from Vale’s Manitoba Division containing up to 0.1% arsenic was investigated as a possible candidate for recovery via the Long Harbour flowsheet. Test work was conducted at Vale’s Technology Center in Mississauga, Ontario, on the unit processes of autoclave leaching, arsenic fixation, final neutralization of both leach solutions and residues, and examination of residue stability over an 18-month period. With positive results, a plant trial was initiated in late 2021/early 2022 validating arsenic could be stabilized on the commercial scale and adhere to environmental regulations related to its deposition in the residue storage area. This paper discusses the challenges and opportunities associated with processing Manitoba nickel concentrate at the Long Harbour Processing Plant.