Collapsed As-Built Dashboard Ontario Community College - B2 (Demo Data) · AACE RP 29R-03 §3.8 (Modeled / Subtractive / Single Simulation)
Anchor check: the schedule’s stored finish and the CPM-recomputed finish agree (2026-09-30).
Removing all 3 delay events from the as-built network pulls the project finish from 2026-09-30 to 2026-09-01, attributing 20 working days to the events analyzed. The removals act on the driving chain A4180 → A4190 → A4240; the collapse sequence at A-03 shows the finish stepping as each event is removed. The result is dual-method validated: the MIP 3.3 windows analysis reports 21 wd against this report's 20 wd, a gap of 4.8% (AGREE).
Methodology
AACE RP 29R-03 §3.8 · Modeled / Subtractive / Single SimulationFor each documented delay event, the as-built network is cloned, the event's impact removed (by either shorten, reducing affected activity durations, or remove, deleting the affected activities and their TASKPRED edges), and the CPM forward pass re-run. The resulting project finish is the but-for [event] date. The differential between the as-built finish and the but-for finish is the event's attributed impact under the Modeled / Subtractive method.
Configuration. Default removal method is shorten (a per-event override applies when an event specifies its own removal_method). Contractor filter: No, every event in the input list contributes to the cumulative pass.
Subtractive
Single Simulation
- AACE RP 29R-03, Forensic Schedule Analysis Recommended Practice, §3.8 Modeled/Subtractive/Single Simulation (Collapsed As-Built / But-For), §3.9 Modeled/Subtractive/Multiple Base.
- SCL Delay & Disruption Protocol, 2nd ed., §11.5: TIA (forward) vs Collapsed As-Built (backward).
- Wickwire et al., Construction Scheduling, 4th ed., Ch. 10: But-For analysis; dual-method convergence as evidence of method reliability.
- Bramble & Callahan, Construction Delay Claims, 4th ed., §9.05: Collapsed As-Built methodology; practitioner-consensus dual-method convergence cut-offs.
The subtractive method is sensitive to the input impact_days values. A ±20% input uncertainty on the per-event impact durations can swing the cumulative result by a similar amount. CPP practice (not an AACE 29R-03 §3.8 requirement) is to run a schedule risk analysis (Monte Carlo with duration uncertainty distributions) against the input durations and report the P50 ± P90 range alongside the deterministic figures shown here. This dashboard reports a deterministic point estimate; opposing counsel should be expected to attack the input uncertainty on cross-examination. See the schedule-risk-analysis skill output for the corresponding probabilistic envelope.
When two delays affect the project simultaneously on overlapping paths, the subtractive method (this skill) and windows analysis (forensic-delay-analysis MIP 3.3) can produce different attribution. The cumulative pass treats all delays as additive; if the project has concurrent owner-vs-contractor delays or two parallel critical chains, run a concurrent-delay analysis (forensic-delay-analysis windows method, AACE 29R-03 §3.3) and reconcile against the output below. Dual-method gaps >10% are a strong signal that concurrent delays are present.
Per-Event Subtractive Pass
clone · remove impact · re-run forward passFor each delay event below, the as-built network was cloned, the event's impact removed using the indicated method, and the CPM forward pass re-run. The resulting "but-for" finish and computed impact are shown.
| Event ID | Name | Affected Activities | Removal | As-Built Finish | But-For Finish | Impact (wd) | Responsible | Contractor? |
|---|---|---|---|---|---|---|---|---|
| E1 | AHJ / commissioning-agent hold on MEP and elevator commissioning | A4180 | shorten | 2026-09-30 | 2026-09-23 | 5 wd | Owner | N |
| E2 | Owner-directed re-sequence of integrated systems testing | A4190 | shorten | 2026-09-30 | 2026-09-23 | 5 wd | Owner | N |
| E3 | Contractor punch-list and deficiency re-work | A4240 | shorten | 2026-09-30 | 2026-09-16 | 10 wd | Contractor | Y |
For each event: the duration removed and the basis used, plus what drives the but-for finish. A completed activity whose finish is on or before the data date cannot pull a successor whose start is pinned at the data-date floor, so the impact can legitimately be 0 even when a duration was removed. That sensitivity is disclosed below.
Cumulative Roll-Up
all events removed together · single subtractive passDual-Method Gap
MIP 3.3 (Windows) vs MIP 3.8 (Subtractive)Both methods converge within the 5% practitioner-consensus tolerance. The forensic conclusion is dual-method validated.
Thresholds: AGREE ≤ 5% · WARN 5-15% · INVESTIGATE > 15%. Bands are forensic-engineering practitioner consensus per Bramble & Callahan §9.05 and Wickwire et al. Ch. 10. They are NOT codified numeric cut-offs in AACE RP 29R-03 (which permits more than one method in §5 but describes no cross-check and publishes no numeric tolerance percentages).
Diagnostics & Warnings
67 diagnostics · 6 detectors — all listed67 diagnostics across 6 detector codes. The triage strip below states, per detector, what its findings mean for the reliability of the but-for result; the full registers follow, grouped by detector, every entry listed.
| Detector | ALERT | WARN | INFO | What it means for the but-for result |
|---|---|---|---|---|
| cpm/out-of-sequence | 11 | 0 | 0 | Work progressed out of logic order, so the as-built chain the removal walks may not be the chain the work actually followed; the removed duration can land on the wrong path. |
| cpm/post-data-date-actual | 0 | 41 | 0 | Actual dates are recorded after the data date, so the as-built network is partly forward-looking and the finish the collapse measures against may rest on unstatused work. |
| cpm/constraint-noop | 0 | 7 | 0 | A date constraint affected (or failed to affect) the pass as noted. A constrained date can hold the but-for finish in place and mask logic-driven movement. |
| cpm/constraint-applied | 0 | 3 | 0 | A date constraint affected (or failed to affect) the pass as noted. A constrained date can hold the but-for finish in place and mask logic-driven movement. |
| cpm/completed-succ-skipped-in-backward | 0 | 0 | 4 | Backward-pass float through completed chains is not meaningful; the forward-pass but-for finish is unaffected. |
| collapsed-calendar-basis | 0 | 0 | 1 | States which calendar the working-day figures are counted on (or that it had to be guessed). A different calendar changes working-day magnitudes, not the but-for dates themselves. |