Mitigating Occupation Program Risk through Construction Method Study & Lean Thinking


The leadership team responsible for delivering a $480M rail infrastructure project had identified program contingency risk in the 93-day occupation of the rail corridor.

The project included constructing a 2.5km rail bridge. The viaduct substructure and superstructure was the critical path in the occupation program.

Due to the inherent constraints of operating in a densely populated suburban area, the program was tight; and the risk of bad weather due to completing construction during winter compounded this.

Program overrun would create extensive commercial pressure. A risk mitigation plan was required.


Our team facilitated an end-to-end study of the construction program scheduled for the occupation and identified risks to overrun and opportunities for improvement.

The study utilised a series of Lean methods to engage the project team in analysing and challenging the construction methodology.

The team facilitated the following activities:

  • Value Stream Map workshops visualised each step of the construction process hour-by-hour.
  • Theory of Constraint principles enabled the team to understand how bottlenecks in the construction process would restrict throughput.
  • Takt Time rules allowed the team to assess the imbalance between process throughput and the required construction outputs.

to assess the imbalance between process throughput and the required construction outputs.


The activity identified a series of requirements to mitigate program risk and opportunity to reduce overall construction cost:

  • The pile cap construction method required a reduction from 58-hours per cap to 48-hours.
  • Onsite L-beam inventory should be increased from 69-units to 92-units prior to occupation.
  • A detailed traffic simulation was needed to identify material delivery constraints.
  • The plan for pre-cast crossheads and piers increased costs significantly whilst providing minimal program value.


  • Program contingency expanded from 19% to 25%.
  • Further investable options would enable a 31% contingency.
  • 93-day occupation completed 2-weeks ahead of schedule.