Client Asks to Absorb a Chiller Change Into the Baseline
A 14-month wastewater treatment plant is 30% complete when the client adds a 400-ton rooftop chiller. The chiller requires a new structural platform, a 6-week fabrication lead time, and a 3-week crane pick. The original baseline had a 10-day contingency on the roof structural steel. The client's project manager sends an email: 'Just update the baseline in P6-change the original durations and add the chiller into the existing roof activities; we will sort out the change order later.' The contractor's scheduler knows that the roof steel was already erected and that a 12-day out-of-sequence progress update is pending. The contract requires a time impact analysis (TIA) for any change over $250,000. The change is valued at $1.8M. The client wants no extension to the 14-month completion because the baseline shows 22 days of total float on the roof.
1. Evaluate the client's instruction to update the baseline directly. What baseline-management and change-control principles are violated?
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Directly changing the baseline violates baseline integrity. The baseline is the approved scope, schedule, and cost against which performance is measured; it should not be retroactively edited to absorb a change. The change should follow the contract's change-control process: change request, impact assessment, time impact analysis, change order, and, if approved, a new baseline revision. Adding the chiller to the existing roof activities destroys traceability: the original activities and durations must remain for earned-value and delay analysis. The instruction also ignores the 12-day out-of-sequence progress; updating actuals into a stale logic model will produce false float. Separate the baseline, the current schedule, and the change fragnet. The contractor should not begin work on the change without a directed change or written authorization, and the scheduler should document the instruction and the contract requirement. If the client insists, escalate in writing and preserve the original baseline as a separate version.
2. Describe how to perform a prospective TIA for the chiller and how to treat the 22 days of float and the 10-day contingency.
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Perform a prospective TIA: take the current schedule at the data date, create a fragnet for the chiller with its own activities-design, fabrication (6 weeks), platform installation, crane pick (3 weeks), tie-ins, and testing-and logical ties to the roof and MEP work. Insert the fragnet into the current schedule, run CPM, and compare forecast completion with and without the change. Do not use the baseline's 22 days of roof float as automatically available; float belongs to the project and may already be consumed. Check the 10-day contingency: contingency is a risk allowance, not a free schedule buffer; if it was for roof-steel risk and is already used, it cannot be double-counted. The TIA should show the change's driving path and the extension, if any. If the change consumes float but does not extend completion, document that; if it extends, issue a change order for time. State clearly whether the 22 days is still available in the current schedule, not just the baseline.
3. What should the scheduler do about the 12-day out-of-sequence progress before running the TIA?
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Correct the out-of-sequence progress before the TIA. Out-of-sequence means the schedule shows work starting or finishing before its predecessor, often because actuals were applied without updating logic. It can create false negative or positive float and distort the critical path. Status the schedule to the data date, fix the logic, and re-run CPM. Only then insert the chiller fragnet. If the out-of-sequence is 12 days, it may already have consumed float or changed the driving path; a TIA on an uncorrected schedule is not defensible. Document the correction and the data date in the TIA, and keep a copy of the pre-correction schedule for audit. If the client disputes the correction, the scheduler should show the logic violation and the affected paths.