Consultant Corner: The Hardest Case to Prove: Causation in Cumulative Impact Claims

Introduction

Cumulative impact claims are among the most challenging disputes in construction law. Often called the “silent killer” of project productivity, these claims allege that the combined effect of numerous changes, not any single one, causes significant inefficiencies, disruption, and cost growth.

While contractors may have little trouble showing that productivity declined or costs escalated, the real difficulty lies in proving causation. Dispute resolution forums require more than an assertion of widespread disruption; they demand a disciplined demonstration that the inefficiencies were caused by the accumulation of changes, were unforeseeable, and were not attributable to other factors such as poor management, labor shortages, or weather.

From a practitioner’s perspective, this article examines the unique challenge of causation in cumulative impact claims and provides insights into the analytical approaches attorneys and experts can leverage when these disputes arise in arbitration, mediation, or litigation.

What Makes a Cumulative Impact Claim Distinct

Unlike discrete claims tied to specific events, cumulative impact claims argue that individually manageable changes, when combined over time, erode productivity in ways no single change order captures. The argument is that frequent owner-directed modifications, design clarifications, and scope adjustments collectively fragment workflow, cause rework, stack trades, and disrupt sequencing.

These claims are most often seen on large or complex projects where constant change becomes the norm. Yet the very nature of these claims, which focus on systemic disruption rather than isolated events, make them difficult to prove.

The Burden of Causation

To succeed in a cumulative impact claim, a contractor must meet three key burdens:[1]

1. Establish a causal link between the accumulation of changes and the alleged disruption.
2. Show that the impact was unforeseeable at the time of contracting or when changes were accepted.
3. Demonstrate that the disruption was not caused by other factors, including the contractor’s own shortcomings.

Each of these burdens presents its own challenges.

Establishing the Causal Link

Courts and arbitral panels expect more than evidence of a high volume of change orders. The claimant must demonstrate how the timing, frequency, and interaction of changes disrupted workflow and reduced productivity. Simply pointing to the number of changes is not enough.

The most effective claims weave together contemporaneous records, project schedules, and productivity data to tell a compelling story of cause and effect. Without this, even a project riddled with disruption may fail to meet the evidentiary standard.

Demonstrating the Impacts Were Unforeseeable

Most contracts allocate risk for changes and disruptions to some extent. To establish entitlement, the contractor must show that the cumulative impact went beyond what the parties reasonably contemplated. If disruption is viewed as an expected byproduct of the contract or if the contractor failed to raise concerns in real time, the claim often collapses.

For attorneys and other dispute resolution professionals, the key question becomes whether the alleged cumulative effect was an unexpected consequence of the changes, or simply a foreseeable outcome the contractor should have anticipated.

Isolating Cumulative Impact from Other Causes

Even when disruption is proven, it must be distinguished from other contributing factors. Poor planning, resource shortages, labor disputes, weather events, or concurrent delays can all blur causation. Adjudicators are especially wary of claims that appear to mask contractor inefficiencies under the guise of cumulative impact.

Strong claims directly address and separate out these other factors, demonstrating that while multiple causes may exist, the cumulative effect of owner-directed changes was a substantial driver of productivity loss.

Analytical Approaches for Demonstrating Causation

Attorneys representing contractors or owners in these disputes must rely on expert analysis. Several methodologies are commonly used, each with strengths and limitations.

System Dynamics Modeling

System dynamics is becoming one of the most comprehensive approaches for cumulative impact claims. It simulates how projects evolve over time based on interactions such as workforce efficiency, rework cycles, frequency of changes, and schedule compression.

Unlike traditional methods, system dynamics captures the cause-and-effect feedback loops, time delays, and nonlinear behavior that characterize cumulative disruption. Forensically, it allows an expert to demonstrate not just that productivity loss occurred, but how and why it occurred across the life of the project.

For attorneys, this provides a transparent and compelling narrative, one that helps decision-makers understand the mechanisms of cumulative impact in a way that simple cost comparisons cannot.

Measured Mile and Modified Measured Mile

The measured mile method compares productivity in an “unimpacted” portion of the project to a disrupted portion. Where no fully undisturbed period exists, a modified measured mile may be used.

These methods are widely accepted but have significant limitations in cumulative impact disputes:

• On heavily disrupted projects, no truly unaffected period may exist.
• Overlapping disruptions make it difficult to isolate impacts.
• External events such as weather or supply chain delays can confound results.

While useful as part of a broader evidentiary framework, measured mile analyses rarely succeed on their own in proving entitlement to cumulative impact claims.

Total Cost and Modified Total Cost Approaches

In some cases, contractors present claims by comparing actual costs to the original estimate, attributing the difference to disruption. These “total cost” approaches are generally disfavored in dispute resolution. They are often seen as blunt instruments that attempt to shift all overruns to the owner without isolating causes.

Such claims typically succeed only when no other method is feasible and when the contractor can show that its estimate and actual costs were reasonable and that it bore no responsibility for the overruns. In practice, this is a high bar that few claims can meet.

Case Study: J.A. Jones Construction Co. – Limits of Measured Mile in Pervasively Disrupted Projects

Source: Appeal of J.A. Jones Construction Co., ENGBCA No. 5528 (1995)

This case is directly relevant to the central themes of this article, particularly the difficulty of proving causation, the challenge of identifying truly “unimpacted” work, and the limitations of relying on single-method analyses such as measured mile. J.A. Jones illustrates the precise evidentiary hurdles that arise when cumulative disruption affects every phase of a project, making traditional analytical techniques insufficient on their own.

Summary of the Dispute

The contractor was engaged in constructing a federal courthouse that experienced continuous design revisions, late approvals, and owner-driven scope adjustments. Although each individual change appeared modest, their frequency and overlap disrupted sequencing, increased trade interference, and eroded workflow stability. J.A. Jones sought recovery for cumulative impact, arguing that the aggregation of owner-directed modifications caused substantial productivity loss.

To demonstrate inefficiency, the contractor attempted a measured-mile analysis. However, the Board found that the project had no period of unimpacted performance, which rendered the measured-mile results non-applicable. Because disruption permeated all phases of the work, there was no valid baseline against which to measure labor productivity. The Board therefore rejected the measured-mile approach, not because cumulative impact did not exist, but because the analytic method was unsuited to the circumstances.

Rather than dismiss the claim outright, the Board examined contemporaneous project documentation, including daily reports, manpower records, evidence of resequencing, and patterns of workflow fragmentation. These materials helped establish that owner-directed changes materially contributed to productivity degradation, while also allowing the Board to separate owner-caused disruption from contractor-driven inefficiencies.

Relevance to Causation and Expert Analysis

J.A. Jones demonstrates that even when every available productivity comparison is distorted by widespread disruption, cumulative impact may still be recoverable if the claimant provides a clear, evidence-based causation narrative. The case underscores that:

• measured mile is not universally applicable;
• causation must be supported by multiple forms of evidence; and
• contemporaneous project documentation often becomes the most persuasive tool.

This case reinforces the need to build cumulative impact claims around mechanisms of disruption, not simply numerical comparisons.

Why This Matters for Attorneys in Dispute Resolution

For those litigating or arbitrating cumulative impact claims, the challenge is not proving that disruption occurred—most large projects experience it. The challenge is proving causal entitlement: that the disruption was caused by cumulative changes, was unforeseeable, and was not caused by the contractor.

Attorneys must therefore focus their strategy on evidence that ties productivity losses directly to the aggregation of changes. This often requires:

• Contemporaneous documentation such as daily reports, meeting minutes, and correspondence.
• Forensic schedule and productivity analysis performed by qualified experts.
• A clear narrative that distinguishes cumulative disruption from other project challenges.

The most effective cases combine these elements into a story that is accessible to arbitrators, judges, and mediators, many of whom may not have technical construction backgrounds.

Practical Takeaways

• Document early and often. Contractors who fail to flag concerns about cumulative disruption during execution often undermine their own claims later.
• Build causation step by step. Strong claims link specific clusters of changes to measurable impacts, supported by contemporaneous records.
• Beware of overreliance on formulas. No single method, including measured mile, total cost, or otherwise, will suffice in isolation. Use multiple approaches to triangulate the truth.
• Anticipate skepticism. Dispute resolution forums are wary of cumulative impact claims, viewing them as attempts to shift unanticipated costs. Expect to face rigorous scrutiny on causation.

Conclusion

Cumulative impact claims represent one of the most difficult frontiers in construction disputes. They ask courts, arbitrators, and mediators to look beyond individual changes and recognize a systemic effect that is hard to quantify. Success hinges on causation: proving that inefficiencies were caused by the accumulation of changes, that they were unforeseeable, and that they were not the contractor’s own doing.

For attorneys, the implication is clear: these cases require careful strategy, strong documentation, and expert analysis that can withstand cross-examination. Without that foundation, even genuine disruption may fail to result in recovery.

[1] AACE International’s Recommended Practice RP 130R-23, Demonstrating Entitlement to Cumulative Impact Claims in Construction, provides additional detail in this area from a practitioner’s perspective.

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Author Stephen P. Warhoe, PhD, PE, CCP, CFCC, FAACE, is a Senior Director at Arcadis and an expert in delay, disruption, and productivity loss on complex projects. He has nearly four decades in the construction field, is a university professor in construction management, and has testified extensively as an expert witness in construction disputes.

Editor Thanh Do, PhD, PE, is a Director at BRG's Global Construction Practice. He specializes in root cause investigations of structural failures, standard of care evaluations, construction and design defect analysis, Design-Build delivery, early dispute resolution, and trial visualization.