Schedule Updating and Project Control - Construction Project Scheduling and Control - page 204

performance. The CPI for Rock Excavation is 0.88 (substantially low),
whereas it is 0.96 for the entire operation.
2. When we look at the schedule, the only meaningful number is the over-
all schedule variance, which tells us that the Mass Excavation opera-
tion is almost 2 days behind schedule. Looking at individual schedule
variances may be misleading. It is possible that the contractor planned
to focus effort on one area at the expense of other areas. In this case,
both Common Earth and Rock are on schedule; Clay is behind.
3. Let us consider the Mass Excavation activity as part of the total exca-
vation operation, TOB11100, which includes, in addition to TOB11110
Mass Excavation, TOB11120 Special Excavation, as shown next:

Work Breakdown Element Level

TOB10000 Tampa Office Building 1

TOB11000 Substructures 2

TOB11100 Excavation 3

TOB11110 Mass Excavation 4

TOB11111 Common Earth Excavation 5

TOB11112 Clay Excavation 5

TOB11113 Rock Excavation 5

TOB11120 Special Excavation 4

TOB11121 Confined Areas Excavation 5

TOB11122 Other Special Excavation 5

If the same subcontractor is in charge of the TOB11120 Special
Excavation operation, he may also be concentrating the effort on one
operation at the expense of the other (Mass Excavation and Special
Excavation). In this case, we will not be able to tell how much the
contractor is ahead or behind schedule until we look at the entire exca-
vation operation, TOB11100. In contrast, the cost variance is activity
specific and is a true indicator at any level.
4. Looking at forecasted variances indicates that, if work continues at the
same pace and in the same pattern, the Mass Excavation operation will
finish 6 days behind schedule and with a $6,436 deficit. This situation
is certainly a reason for concern for the project management team.
The project manager must try to mitigate this outcome.
5. In the WBS shown in comment 3, we have five “levels of control.” A
typical superintendent or project manager may want to look at earned
value at level 4 or even level 5. Someone in upper management may
look at level 2 or 3, but if an unsatisfactory number is spotted, he or
she may want to go to a lower level, such as level 4 or 5, for the specific