Cost growth associated with underestimating and excessive technical risk is compounded by knock-on impacts to other projects. As costs rise for some projects, or their patterns of expenditure move due to delay, other projects need to be "re-profiled" to keep the programme affordable, at least in the near term. This project shuffling and reprioritisation is almost certainly suboptimal, and additional costs of overhead, working capital and contracting penalties will be incurred in the process. A significant proportion of these costs will find their way into the EPP over time, in the form of modest, but relatively continuous increases in the cost to completion.
Although delay impacts may appear second order, when applied over a significant proportion of the forward EPP over successive years, they will have a growing detrimental impact on near term productive output, as more and more of the in-year resources are required to cover the overheads and standing costs for delivery capability that is shifted out in time.