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Time Impact analysis

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Akhil Chandran
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Is there any global standard for preparing EOT?


Tom Boyle
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AACE International Recommended Practices:


(This covers prospective EOT applications like Patrick describes.)

29R-03:  FORENSIC SCHEDULE ANALYSIS (2011 - 134 pages)

(This RP seems to be aimed at practicing forensic analysts and those who employ them - i.e. lawyers.  It attempts to describe and categorize a large number of forensic, i.e. retrospective, analysis methods, using unconventional terminology.  The RP describes some methods that are viewed as less valid among practitioners in some regions, and one criticism is that the inclusion of such methods tends to validate them.)


American Society of Civil Engineers (ASCE) Standard:

ANSI/ASCE/CI 67-17:  SCHEDULE DELAY ANALYSIS (2018 - 25 pages)

(A clear set of 35 guidelines to be used in any analysis methodology, though an explicit methodology is not described.  This is aimed at application in USA courts.)

Patrick Mullen
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Hi Akhil,

I know I'm a little late to the party but thought it was a good question. I wrote a pretty in-depth article on how I typically approach creating a time extension request when I'm working with the Contractor.

The very first thing that I do is read the Project's Specifications as sometimes that will provide a roadmap for how to prepare the request. Often times however, the specifications are vague and I'm left with developing the impact using general industry acceptable standards. With that, there are two types of delay events: retrospective (backwards looking) and prospective (forward looking). Retrospective analysis, in my opinion, is more complex so I'll save that for another time. I'll assume this is a delay to the project that has either just occurred, or you have enough information to put together a sequence that will occur in the future. Here's how I would approach a time extension in this sort of an instance:

  1. Develop the timeline for the changed scope/delay event. Get a rock-solid sequence where the dates correspond with the project documents that explains how the Contractor was impacted.
  2. Choose the "pre-impacted" schedule file. Identify the starting point to the delay event, and choose the schedule file that takes into account all of the progress on the job right before the delay event kicked off. If this is a forward-looking delay, or it's an impact that you just experienced, you would typically use the progress update that was just submitted.
  3. Insert the delay sequence (from step 1) into the pre-impacted schedule file to see if it had a net effect on any of the contract milestones.
  4. If it did, did it push the milestone passed the contract date? Make sure it's not just float that is being consumed.
  5. Also, is there anything that was happening concurrently that may have also impacted the project? It's a good thing to account for that in the analysis.
  6. If the completion date was pushed beyond the contract date as a result of the delay, then I go ahead and put a write-up together explaining the background of the delay event, the methodology used to develop the analysis, and the actual request stating what the Contractor is seeking (i.e., an "excusable, compensable time extension", or "excusable, non-compensable time extension).

I'll close by saying that because projects are so different, and delays can be very complex, the way in which you communicate the delay to the Owner is going to vary widely project to project. This methodology might work in many cases, but not necessarily in all cases. Keep that in mind when you're putting your request together.

Hope that helps! Best of luck.


Akhil Chandran
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what is the meaning of contemporaneous schedule baseline update?

Warren Sika
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I believe there is no global standard for preparing EOT. Even the type of technique you use can be chosen depends on the type of delays. Most of the time am using Impacted as Planned as it is easier to use though maybe most of Planners who work in the Consultancy will not agree.