Over the last year at Clarabelle Mill, three circuit reconfigurations were implemented. One circuit reconfiguration, A Cleaning', was initiated due to a furnace failure at the smelter complex, and two of the circuit reconfigurations, increased copper (Cu) separation' and the Interim IsaMill circuit', were seen as opportunities to increase cash flow through the mill. A Cleaning and the Interim IsaMill circuit took advantage of engineering design already completed for a major capital project. The engineering for each was modified, as needed, and construction of the required portions of the capital project was fast tracked. The increased Cu separation circuit change used existing test and plant equipment to increase the plant Cu concentrate production. Implementation of the projects required teams that included operations, maintenance, technical support, project management and capital project resources. This paper discusses the business reasons driving the changes and the forethought or synergies with other work, which made them a success, and what was learned through each project. CITATION:Taylor, A, Lawson, V and Barrette, R, 2012. Responding to the challenge - Necessity driving circuit change, in Proceedings 11th AusIMM Mill Operators' Conference, pp 247-254 (The Australasian Institute of Mining and Metallurgy: Melbourne).