Big Dig Tunnel Ceiling Collapse

On July 10, 2006, a suspended concrete ceiling panel detached from the Interstate 90 Connector Tunnel in Boston and fell onto a passenger car, fatally injuring one person.

The suspended ceiling panel weighed approximately 26 tons, had been in place since the year 2000 and was attached to the tunnel using adhesive anchors. The adhesive anchors were identified early on as the source of the failure. CTLGroup’s challenge was to determine why the adhesive anchors failed by investigating whether there was an issue with design, installation, material quality, or something else.

CTLGroup reviewed relevant standards to determine the suitability of the adhesive anchors to suspend the ceiling panel. We also reviewed the original tunnel design to assess whether the ceiling panels had been properly designed and constructed. Additionally, we conducted laboratory testing to independently measure the performance of the adhesive anchors. Our specialized testing capabilities come from significant experience with concrete anchor testing and our in-depth experience with related qualification tests and standards such as ASTM, ACI, and ICBO. Our range of knowledge gives us our ability to provide authoritative anchor evaluation in construction and litigation resolutions such as this.


Civil Infrastructure

Litigation & Insurance


Consulting Services

Forensic Engineering

Catastrophe Response

Construction Accidents & Failures

Design, Construction, and Material Defects

Structural Collapse Investigation

Structural Condition Assessment

The investigation into the collapse and repair of the ceiling and tunnel caused a section of the project to be closed for almost a full year, causing massive traffic backups.


Year of Collpase


Project Completion

26 Tons

Panel Weight

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