Issues Regarding Total Time and Stage 1 Time
A reasonable question to ask is how can the planner be assured of choosing
the right overall time (i.e., equivalent to 100%) and why should the learning
always take 30-35% of that value? Should it not be possible to contemplate a
36-storey high-rise, rather than 24, and still achieve the Stage 2 efficiency
of the 24 storey high-rise in the first six floors?
The practical reality is that if the building is that much larger in all likelihood
the whole scale of the project operation is correspondingly larger and will be
planned and organized accordingly. This includes increased use of temporary materials,
plant, equipment and site organization all optimized to suit the larger project.
The planned time must also be realistic and achievable, especially if it is
being compressed. Having chosen this time, it is essential that all the supporting
logistics of the site, including management, supervision, equipment, supplies
etc., are all present to support this choice. Failing this, it is the authorÍs
observation that the job then "takes on a will of its own" wherein
it charts its own progress record. Thus, it is the organizational culture associated
with the site that ultimately determines the final outcome.
As one example of what can go wrong, Figure 15 compares
actual production of rock excavation with planned production on a less than well
managed site preparation contract. Partly due to changes, final quantities
were significantly higher than originally anticipated, the planned peak level
of production was never reached, and Stage 1 of the S-curve took more time. Not
surprisingly in this case, the whole contract took a lot longer to complete
and ended in litigation.
Figure 15: Comparison of actual vs. planned production of bulk rock excavation.
Percent cumulative total is based on original estimate of 133 000 m3
(174,000 cubic yards)
From the authorÍs personal records of an actual contract.