Project phases post-sanction should be minimised if possible.
I found that EPCM Designers became so focussed on completing a phase that progress and attention with the following phases usually suffered.
A looming construction deadline forces them to check and complete their design.
A future construction deadline is then regarded as secondary (less checks/plenty of time in hand) until it also looms.
Also construction flushes out design and procurement omissions. Resolving these issues for subcontractors usually requires resources which have moved on to the following phase.
Client teams are also affected due to having to be periodically mobilised and then demobilised.
However the impact of project phases could be minimised with robust project management of deliverables and issue resolution
In general, every additional project phase introduces more handovers, reviews, and potential delays. While some gates are necessary for governance and risk control, too many can slow execution and inflate costs. Streamline the phase structure where possible—combine steps that don’t add real value and focus on decisions that genuinely move the project forward. Fewer, sharper phases mean faster delivery and lower overhead.