In June 2021, we had an independent costing firm work with us to establish a baseline cost estimate. All of the contingencies, risk reserve and escalation were factored into the cost breakdown.
If we look at contingencies, we have design contingency as well as construction contingency. It maps out well, given the complexity and scale of the Centre Block compared to other projects in the precinct. For example, the West Block had contingencies of 35%. We're using 45% for the Centre Block, given the increased complexity with all of the additional heritage material in particular.
For the risk reserve, for example, we used 25% risk reserve on the West Block. We're using a range of 15% to 35%. That's how we get to that range of $4.5 billion to $5 billion. It's that range in the risk reserve. The reason we've used a range in this case is twofold. One part was that we still did not have all of the functional requirements locked down with Parliament, and, the other was that given the pandemic context of escalation rates in materials, equipment and rates of labour, we wanted to make sure we had some additional absorption to be able to take into account the potential that escalation rates would take a while to return back to normal.