Disputes involving delays to the completion of a project will often require analysis using CPM, Critical Path Methods, to establish the extent of critical delay. As the acronym implies, this is because it is only delay critical to completion that would normally attract prolongation costs, through an extension of time, EOT, termed compensable delay, or LADs, Liquidated and Ascertained Damages.
Both the Society of Construction Law (SCL) and the American Association of Cost Engineers (AACE) make clear that in order for claims for either prolongation cost or LADs to be successful, delay must be critical to project completion.
SCL Delay and Disruption Protocol 2ND Edition, Core Principles No.4. ‘The Contractor potentially will be entitled to an EOT only for those events or causes of delay in respect of which the Employer has assumed risk and responsibility (called in the Protocol Employer Risk Events) that impact the critical path.’
The American Association of Cost Engineers (AACE) in its ‘International Recommended Practice No. 29R-03, Forensic Schedule Analysis’ in section 1.5 ‘Underlying Fundamentals and General Principles’, subsection B6, ‘Delay Must Affect the Critical Path’.
The important takeaway from both of the above is reference to ‘the critical path’. The aim of CMP analysis performed retrospectively is to establish and interrogate the as-built critical path of the project from start to finish.
If project delays have not been addressed during the course of the works i.e. Prospectively, making use of agreed programmes and the planned critical path to predict completion, then Retrospective analysis techniques should be used.
The four retrospective CPM analysis techniques identified by the SCL, and explained in detail by the AACE, are;
Time Slice Windows Analysis
This method involves establishing what has been termed the contemporaneous or (and confusingly) the ‘actual’ critical path within a series of regular windows. Results from this method of analysis produce a series of mini critical paths that may not correspond to the real as-built critical path of the project. A common-sense review is recommended to ensure results align with the SCL and AACE principles referred to above.
As-Planned v As-Built Windows Analysis
Similar to the Time Slice method above, this method is a simple comparison and relies less on computer software. It is somewhat open to manipulation as the windows are not necessarily based on regular programme updates but selected events. It is limited to simple and short duration programmes where the planned critical path remains, however delayed, in the as-built scenario. And again, a common-sense review should be undertaken.
These window analysis methodologies maybe the origins of the terms referring to forensic delay analysis as ‘the dark arts’ or ‘smoke and mirrors’. This is perhaps unfair; both these methodologies can give overall project critical delay when properly implemented and sense checked.
Retrospective Longest Path Analysis.
Perhaps the purest form of delay analysis. This method requires the analyst to work backwards through an as-built programme establishing in reverse the critical path of the project in its as-built situation from finish to start. Examination of this real as-built critical path will reveal critical change, and activity prolongation.
Collapsed As-Built Analysis
The least commonly used delay analysis technique due to the complexity of its application in all but the simplest of programmes. It requires establishing a logically linked computer model of the programme activities in the as-built situation. Once delay and causation of delay are established, these periods are subtracted, or made zero duration and the model rerun and the effect on completion observed.
These techniques all benefit in their application from agreed and comprehensive baseline programmes, regular updates of the agreed programme with progress information input contemporaneously, and other comprehensive contemporaneous records.
Each of these delay analysis techniques, when applied appropriately, has the ability to identify real critical project delay, when during the course of the works that critical delay occurred and, with due reference to liability, the likely extension of time or damages periods that may be due.
Authored by Mr Chris Milner, Delay Expert
