CHAPTER FIVE: CASE ONE-CCSR PROJECT
5.2 PPC and Reasons
Several kinds of data were collected: PPC and reasons, auxiliary documents such as phase and master schedules, and the observations of the
researcher. PPC and reasons data was collected each week from 12/24/97 through 3/3/98, during the wettest season in the San Francisco area in recorded history. Although the project had taken weatherizing precautions to minimize weather-related delays, such as type of fill material and drainage systems, nonetheless rain was
20 A phase was conceived in terms of a relatively independent facility system. For
by far the most frequently cited reason for failing to completed assignments on weekly work plans
Table 5.1
I.
CCSR-Weekly Planning Cycle
Table 5.2
CCSR Weekly Planning Cycle
GC and subs meet to: 1) status this
week's plan, identify reasons for
failing to complete planned tasks, and agree on actions to prevent repetition, and 2) finalize the
lookahead
* The short interval schedule covers the construction tasks required to achieve a schedule
milestone (e.g. slab-on-grade by 2/28/97) and the design and supplier tasks providing needed information and materials. The team develops
a detailed schedule for each phase of the job at least 4 weeks before starting that phase. The phase schedule
then becomes the control schedule for short interval scheduling each week.
* Subs status tasks for these constraints:
contract, design, submittals, matls, prerequisite work, tools & eqpt, space,
labor, other. A/E statuses tasks by specifying the information or decision
needed.
*Both subs and A/E are answering the
questions: 1) If constraints are in your
control, are you confident they will be removed in time? 2) If constraints are not in your control, what help
do you need from others?
Guidelines: 1) Schedule for next
week (Wed thru Tu) only tasks that
have no constraints or have
only constraints you know can be removed in time. 2)
Schedule in the 2nd and 3rd weeks
only tasks you are confident can be
made ready in time. The goal is
100% plan well the team is
achieving its
* GC reviews the phase schedule and master schedule for needed adjustment.
Table 5.2
Wills
II. I D
Activity Start Contract Design Sub mitta
950 Tunnel Lobby -Walls Rebar
3/4/98 1040 Footings 6 & 7
Dowels
3/4/98 1220 Footings 6 & 7
Between A and H Dowels, and Footings E & G Dowels
Between 4.5 and 8
3/4/98
630 Line 4 Wall and Line C
ID Activity Start Contract Design Sub mitta
PPC was measured as shown in Figure 5.1, ranging from an initial measurement of 56%
during the week of 12/24/97 to 70% in the week of 3/3/98. Rain was cited as the reason for 18 plan failures (see Figure 5.2) and
frequently cited reasons were lack of prerequisite work (14), availability or quality of design information (8), and submittals (6).
Removing rain as a reason, weekly PPC would have been as shown in Figure 5.3, with a mean PPC for the research period of 71% (149 of 211
assignments completed), which compared favorably to work flow reliability achieved through previous application of the Last Planner system to projects which were not subcontracted.21
Figure 5.1
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
12/24/97 12/31/97 1/6/98 1/14/98 1/18/98 1/25/98 2/3/98 2/10/98 2/17/98 2/24/98 3/3/98 Week
% Completed
CCSR-Weekly PPC
21 Ballard et al., 1996; Ballard and Howell, 1997
Table 5.3
Week 12/24/97 12/31/97 1/6/98 1/14/98 1/18/98 1/25/98 2/3/98 2/10/98 2/17/98 2/24/98 3/3/98
PPC 56% 86% 57% 67% 73% 75% 50% 53% 74% 44% 70%
Tasks Completed
5 6 8 10 11 18 7 10 23 19 14
Tasks Planned
9 7 14 15 15 24 14 19 31 43 20
Rain 1 1 3 6 2 2 1 2 18
Pre-Requisite 2 2 1 7 2 14
Design 1 1 4 2 8
Submittal 2 2 2 6
Other 1 1 1 1 4
Space 1 2 3
Equipment 2 2
Labor 1 1 2
Materials 1 1
Contract 0
CCSR-PPC and Reasons Data
Figure 5.2
0 5 10 15 20 25
Rain Pre-Requisite Design Submittal Other Space Equipment Labor Materials Contract
Reason
Number Of Ocurrences
CCSR-Reasons for Noncompletion
Figure 5.3
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
12/24/9712/31/97 1/6/98 1/14/98 1/18/98 1/25/98 2/3/98 2/10/98 2/17/98 2/24/98 3/3/98
Weekly PPC Mean PPC
CCSR-PPC without rain
As shown in Table 5.4, reasons for plan failure were categorized as either an Execution Failure or a Plan Failure22. Of the 57 total failures23, 28 were determined to have resulted from some defect in planning, while 29 were attributed to some defect in execution. The 18 failures caused by rain were categorized as execution failures. Disregarding rain, Plan Failures would have amounted to 28 of 38, or 74%, further evidence that to a substantial degree, our fate is in our own hands as regards planning and work flow. In even extreme weather conditions, fully half of noncompletions resulted from poor planning.
22 This distinction was introduced into the Last Planner system in Ballard (1994).
23 Note the absence of detailed information for failures in the week of 12/24/97. Their inclusion would add 4 noncompletions to the total.
Table 5.4 Week 12/31
Activity Reason Type Of Failure
item 6 - Sump Pit Lid Form
Other: Low Priority Plan
Week 1/6
Activity Reason Type Of Failure
item 3 - Underground Plumbing
Rain Execution
Item 13 - East Wall Forms
Design: RFI Execution
Item 32 - Elevator Wall Forms
Pre-Requisite: Not Identified
Plan Item 43 - 2&3 Line
Excavation
Equipment: Backhoe Execution Item 44 - A,C & 4 Line
Excavation
Equipment: Backhoe Execution Item 45 - 2&3 Line Rebar No Excavation Plan Week 1/14
Activity Reason Type Of Failure
item 26 - Elevator 1&2 SOG Pour
Floor Drain Submittals Plan Item 44 - Elevator Pour
Up to Tunnel Level
Shop Drawings Plan
Item 43 - Form South East Quadrant
Waiting Rebar Fabrication
Plan Item 29 - Rebar J Line Waiting On Excavation Plan
Item 7 - Access Panel Submittal Plan
Week 1/18
Activity Reason Type Of Failure
210 - Design Change Rebar Submittals
Not Back Plan
270 - Interior Wall Rebar Submittals
Not Back Plan
A,C, & 4 Line Excavation Productivity/Rain Execution A,C, & 4 Line Rebar No Excavation Plan Week 1/25
Activity Reason Type Of Failure
Excavate Line F and 7 (MidWest)
Rain Execution
Interior Wall Forms Rain Execution
N,Q,L Lines Rebar Installation
Rain Execution
Reveals Location Waiting On Architect Plan RFI Line 7 (Cupertino) Answer Incomplete Plan
Tunnel Piping Submittal Approval Plan
Week 2/3
Activity Reason Type Of Failure
Excavate F Line Rain Execution
Backfill Sump pit Rain Execution
Template Footings A and 4 Line
Rain Execution
Electrical Conduit Elevator 5
Rain Execution
Small and Large Walls Single Form
Rain Execution
Wall Double up @ Tunnel Lobby
Waiting For Inspection Plan
Backfill N-E/S-E Quad. Rain Execution
Week 2/10
Activity Reason Type Of Failure
Plumbing between lines J
& M
Rain Execution
Plumbing Line 6.5 Rain Execution
Small Interior Walls Form Eleveator Jack Drilling / Rain
Execution Small Interior Walls
Double Up
Eleveator Jack Drilling / Rain
Execution Large Interior Walls Form Eleveator Jack Drilling /
Rain
Execution Large Interior Walls
Double Up
Eleveator Jack Drilling / Rain
Execution Small Wall Rebar Eleveator Jack Drilling /
Rain
Execution Line L wall Rebar Eleveator Jack Drilling /
Rain
Execution E & G Line Rebar from 2
to 5
Eleveator Jack Drilling / Rain
Execution
Week 2/17
Activity Reason Type Of Failure
Elevator Wal Backfill Rain Execution
Line J Excavation Backfill
Plumbing/Rain/Mud
Execution Line 6.5 Excavation After 6 & 7 Line Concrete Plan Small Interior Wall Forms Design Change Plan
Small Walls Double Up Design Change Plan
Small Walls Rebar Design Change Plan
Perimeter Wall Line 2 Rebar
Design Change Plan
Footings 6 & 7 Rebar Rain Execution
Week 2/24
Activity Reason Type Of Failure
Planter Excavation Space Plan
Interior Small Walls Rebar Change/Permit Plan
Tunnel lobby SOG Sequence Change Plan
Line L Wall Rebar Change/Permit Plan
Line J Footing Rain Execution
Wall Line 2 From A-D Man Power Plan
Week 3/3
Activity Reason Type Of Failure
Footings E&G Excavation Space For Crane Plan
Line J Concrete Rain Execution
Footings 6&7 Concrete Rain Execution
Court Yard Planter Crane Reach Plan
Small Interior Walls Man Power Plan
Pipe Ties In @ Tunne Waiting On Stanford Info Plan
CCSR-Reasons for Noncompletion (detailed and categorized)
5.3 Observations
Subcontractors were not selected based on their understanding or willingness to participate in the Last Planner production control system. They were selected based on traditional criteria such as financial soundness and bid price. Subcontractor personnel
responsibilities within it after coming to the site. Not surprisingly, some were more capable and enthusiastic about participating than others. Even so, the project superintendent continued to use the Last Planner system and reported that eventually all foremen were participating and that they began to hold each other accountable for keeping their weekly work plan commitments. Nonetheless, it would have been preferable both to incorporate participation in the production control system in the selection criteria and subcontracts, and also to have devoted more time and effort to education and training.
Shortly after introducing the system, it became apparent that more active involvement of others besides the site foremen was needed. Subcontractor project managers were invited to attend the weekly meetings and were better able to understand what was going on, and specifically better able to provide status information regarding constraints such as submittals, design issues, fabrication, and deliveries. There was also efforts made to involve the architect and design engineers on the project. Unfortunately, those efforts failed, in part because of the stage of design completion and the fact that the production architect/engineer was on a lump sum contract and concerned lest they run out of money before they ran out of work.
Analysis of constraints was a key element introduced into the Last Planner system on CCSR. Efforts to collect constraints information from subcontractors prior to the coordination meeting were mostly unsuccessful, perhaps in large part because there is no tradition in our industry for such activities. Consequently, much of meeting time was dedicated to data collection rather than planning and problem solving.
5.4 Learnings
Learnings for future projects included:
q Incorporate production control requirements into subcontracts.
q Select subcontractors for their ability and willingness to participate in the production control system.
q Involve owner, architect, and engineers in the production control process; preferably from the beginning of design.
q Send to subcontractor project managers by email or fax each week constraint reports with the next 5-6 weeks scheduled activities listed and ask them to status their activities and report back. Make sure this happens so meeting time can be used for planning and problem solving as opposed to data collection.
q Use team planning techniques to produce schedules for each phase of work, with participation by foremen, superintendents, and designers.
q Incorporate reasons identification, analysis, and corrective action into weekly coordinating meetings. Otherwise, there is a danger that incompletions become accepted as unavoidable.