Schedule Updating and Project Control - Construction Project Scheduling and Control - page 167

or on the 1st, 2nd, or 3rd of the following month). In this case, the actual
data date is reflected on both the updates and the pay request. However, this
practice may not please the accounting team because monthly accounts may
not be accurate even though the bottom-line total will be correct.

When doing a pay request, you must start the month with a $0 amount for the
cost this period by adding the amount remaining from the last period to the total
cost to date (in Oracle Primavera P6, it is called Store Period Performance ).

“Degressing” an In-Progress Schedule to Create a Baseline Schedule

In some cases, the project schedule is developed as the work progresses. This is not
a good practice. Some activities will have already started or even finished when they
are added to the schedule. In this case, only an as-built schedule exists; there is no
as-planned or baseline schedule for comparison. The scheduler may need to create a
baseline schedule at this late stage (better late than never). The scheduler can do so
by taking a copy of the schedule and reversing all work progress in it to “go back in
time” to the starting point. Doing so requires reversing the progress on all activities,
plus going back from the data date to the starting point of the schedule.
This practice is acceptable (even though it is not the best). However, one impor-
tant pitfall exists. When entering completed (or even started) activities, the scheduler
may ignore their relationships, since they are “history.” Consider the following partial
schedule, for example.

Activity ID Activity Description Duration (Days) IPA

1000 Mobilize 2 —

1010 Clear Land 5 1000

1020 Excavation 6 1010

1030 Dewatering 20 1020

1040 Drive Piles 7 1030 SS-5

— — — —

Suppose that this schedule is being created after the piles have been driven. The
project manager or scheduler might just enter actual dates into the schedule with-
out adding the relationships. He or she might also give actual durations as “original
durations,” not those estimated; see Figure 7.4a. Now, imagine that you “degress”
the project; that is, you reverse all work progress and take the data date back to the
start date; see Figure 7.4b. In this case, you can see all these activities starting simul-
taneously at the beginning of the project. There is no need for an explanation; there
is no logic. For this reason, the logic must always be input, along with estimated
durations. Never forget that this schedule can be—and in most cases is—a legal doc-
ument that may be dissected later to prove or disprove a delay claim. Accuracy is
always important.