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EXHIBIT 073 · INFRASTRUCTURE

I-35W: a design error carried forward

NTSB found inadequate gusset-plate load capacity from a design error, combined with increased loading, led to collapse.

OrganizationMinnesota Department of Transportation
Period2007
LocationUnited States
StatusInvestigated
ImpactCritical
EvidenceOfficial investigation
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Illustrative draft · Source-backed synopsis · Museum analysis marked separately · Updated 5 October 2026

Collapsed I-35W Mississippi River bridge in Minneapolis, viewed looking south after the August 2007 collapse.
Collapsed I-35W Mississippi River bridge in Minneapolis, viewed looking south after the August 2007 collapse.Tom Ruen / Wikimedia Commons. Resized. Photograph · Public domain · Resized for display.
01 / EXECUTIVE SUMMARY

The outcome is only the beginning.

NTSB found inadequate gusset-plate load capacity from a design error, combined with increased loading, led to collapse. [1]

THE PRINCIPLE TO CARRY FORWARD

Review connections as explicitly as major members, and reassess capacity when permanent or temporary loading changes.

02 / THE PROMISE

What the system was trying to do.

Carry road traffic safely across the Mississippi River.

Museum interpretation

The assumption beneath the promise

Museum hypothesis to examine: A long history of use proves that every original structural calculation was correct. This is an analytical proposition to test against the record, not an attributed statement by the organization.

Success should be assessed against the intended service and its safety, reliability, or integrity constraints. A headline outcome cannot tell us whether those constraints were visible, tested, or owned before the event.

03 / WHAT HAPPENED

A sequence, not a single moment.

The intended system

Carry road traffic safely across the Mississippi River.

Source-backed synopsis

The event or review

NTSB found inadequate gusset-plate load capacity from a design error, combined with increased loading, led to collapse. [1]

Source-backed synopsis

The documented aftermath

NTSB recommended stronger design review and load-capacity checks. [1]

Source-backed synopsis
Timeline of documented milestones. Gaps are not evidence that nothing happened. Sources: [1]
04 / WARNING SIGNS

What could be seen at the time?

Documented in cited record

A structural component’s capacity had not been adequately checked. [1]

Who could see it?

See the cited investigation for named teams and the information they held. The synopsis does not infer awareness by every stakeholder.

Why was it not enough?

Signals need interpretation, authority, and a route to action. This is an analytical question, not proof that a warning was deliberately ignored.

05 / KEY DECISIONS

Choices made within constraints.

Museum analysis: Changes in bridge weight and construction loading needed to include connection capacity.

Available alternatives

Pause, test, narrow the operating envelope, seek independent review, or build a recovery option. These are proposed analytical alternatives; feasibility at the time is not established.

Information available

A structural component’s capacity had not been adequately checked. [1]

Incentives & constraints

Delivery pressure, cost, authority, and incomplete knowledge may shape a decision. Their specific weight is not established by this synopsis.

Risk accepted

Ask whether the relevant risk was recognized, who had authority to accept it, and whether affected people understood its implications.

06 / SYSTEM MAP

How conditions connected.

Select a node to inspect its evidence. Links show a proposed analytical relationship, not a measured causal effect.

05 / External context04 / Warning signal03 / Decisions02 / Technical conditions01 / Trigger06 / Consequences
Triggering event

NTSB found inadequate gusset-plate load capacity from a design error, combined with increased loading, led to collapse. [1]

Legend: numbered nodes = analytical categories; dashed arrows = proposed influence or propagation. Museum interpretation informed by the sources below. Feedback and omitted influences require further investigation.
07 / CONSEQUENCES

Beyond the immediate event.

Thirteen people died and many were injured. [1]

Technical impactOperational impactHuman impact

Categories identify documented or relevant consequences. Financial, human, and environmental totals are not estimated here when the source base does not support them.

08 / WHAT THE MODELS EXPLAIN

More than one lens.

Analytical lens

Swiss Cheese Model

Harm can pass through gaps in multiple defenses: organizational influences, supervision, preconditions, and active failures.

In this case, use the lens to examine latent design defect. This application is museum interpretation, not a finding of the original investigation.

Limit: A useful lens, not proof of a universal linear cause. Barriers interact and change over time.

Analytical lens

FMEA

Identify failure modes, their effects, and controls before or during system development.

In this case, use the lens to examine latent design defect. This application is museum interpretation, not a finding of the original investigation.

Limit: Lists can miss interactions and unanticipated operating conditions; scores are not exact probabilities.

Analytical lens

Systems thinking

Examine relationships, boundaries, feedback, and incentives across a whole system.

In this case, use the lens to examine latent design defect. This application is museum interpretation, not a finding of the original investigation.

Limit: A broad lens needs explicit boundaries and evidence to avoid explaining everything after the fact.

09 / COUNTERFACTUALS

What could have changed the outcome?

Counterfactuals are hypotheses. They identify possible intervention points without claiming that a different choice would certainly have prevented the event.

INTERVENTION 2 / During early testing

Test the operating envelope

Exercise realistic boundary conditions and shared dependencies rather than validating components only in isolation.

Cost & feasibility

Requires time and independent review before commitment.

Likely effectiveness

May reduce exposure or consequences. Not quantified; feasibility and effect must be assessed against evidence available at the time.

10 / LESSONS

From hindsight to a usable practice.

FOR FOUNDERS

Review connections as explicitly as major members, and reassess capacity when permanent or temporary loading changes.

Before accelerating hiring or spending, name the assumptions that remain untested and set evidence thresholds for the next commitment.

11 / AFTERWARD

Recovery is another investigation.

NTSB recommended stronger design review and load-capacity checks. [1]

A corrective action is evidence of a response; it is not, by itself, evidence that the wider pattern has disappeared.

12 / SOURCES & EVIDENCE

Follow the record.

Documented claims are linked to sources. Analytical applications, lessons, and intervention proposals are museum interpretation. This draft does not establish motives or a single complete causal explanation.

  1. 1
    ntsb.gov — Minnesota Department of Transportation case record

    Official investigation · Accessed 4 October 2026

Editorial history & limits

Version 1 · 4 October 2026 — source-backed illustrative synopsis created. Independent editorial review is pending. No claim of exhaustive investigation. New sources may alter the analysis.