The Substation Schedule Squeeze
You manage a 9 million electrical substation upgrade. The schedule shows a 26-week critical path through switchgear procurement, civil works, installation, and commissioning. Switchgear has a 16-week lead time and must be ordered before civil works finish. Commissioning needs a 3-week window with the network operator, who has offered only one slot in week 24, and the contract penalty for missing it is 40,000 per week. Your planner reports the schedule was built by linking every activity finish-to-start with no lags, and that civil works has a 5-week duration with no float. A subcontractor has just told you their crew will be unavailable for two weeks in the middle of civil works. The client asks whether the week 24 slot is achievable.
1. Assess whether the week 24 commissioning slot is achievable and explain the schedule logic problem.
Read the worked answer
On the stated logic, the answer is almost certainly no, and the reason is that the schedule is not a valid model of how the work is actually done.
A pure finish-to-start chain with no lags means every activity waits for the previous one to fully complete. In reality switchgear ordering runs in parallel with civil works, and installation can start on completed sections. The 16-week lead time and the 5-week civil duration are being added end to end, which inflates the apparent critical path and hides where the real float is.
The two-week crew gap in civil works sits on the critical path as currently drawn, so it pushes everything by two weeks unless something else absorbs it. Combined with a single commissioning slot in week 24 and a 40,000 per week penalty, the exposure is material.
What to do:
- Have the planner rebuild the logic with genuine relationships: start-to-start with lag between civil works and switchgear installation, and a finish-to-start or finish-to-finish link into commissioning that reflects the operator's requirement.
- Re-run the critical path and identify true float.
- Test the crew gap: can civil works be resequenced, can the subcontractor supply an alternative crew, or can installation start on the first completed section?
- Only then answer the client, with a stated confidence and the specific conditions the week 24 slot depends on.
2. The client wants a single answer on the week 24 slot today. What do you tell them?
Read the worked answer
Give a conditional answer with a date and an owner, not a guess. Saying "yes" to protect the relationship creates a 40,000 per week liability you cannot control; saying "no" without analysis is equally unhelpful.
A defensible response: "The current schedule as built does not support week 24, but I believe that is a scheduling-logic artefact rather than the physical reality. I will give you a validated position within five working days, and here is what it depends on."
Then state the conditions explicitly:
- Switchgear order placed by a specific date, with the supplier confirming the 16-week lead time in writing.
- Civil works resequenced around the two-week crew gap, or an alternative crew secured.
- Installation able to start on completed sections rather than waiting for all civil works.
- The network operator holding the week 24 slot while you confirm, and a fallback slot identified.
Record the 40,000 per week penalty as a live risk with you as owner, and tell the client you are managing it actively. If after five days the answer is still no, you will have the evidence to explain why and to propose the next available slot rather than simply reporting failure.