Case Study: Big Dig Ceiling Panel Collapse (2006)
Project Overview
• Name: Central Artery/Ted Williams Tunnel “Big Dig”
• Location: Boston, Massachusetts
• Year: 2006
• Project Size: Multi‑billion-dollar megaproject
• Scope: Ceiling panel installation in tunnel roof span over highway connector ramp
• Lead Agencies/Contractors: Massachusetts Turnpike Authority /
Category of the Issue, Problem, or Challenge
• Structural
• Materials & Adhesives
• Inspection & QA
Summary of the Issue, Problem, or Challenge
On July 10, 2006, a 20′×40′, ~26‑ton ceiling panel collapsed into the Ted Williams Tunnel connector ramp, killing a passenger and injuring the driver. Investigation revealed epoxy‑anchored bolts as the instigators: adhesive creep and substandard bolt length caused progressive anchor failure. The panel system lacked appropriate design for the tunnel roof sections.
Root Cause Analysis
| Factor | Details |
| Substandard Adhesive & Anchors | Fast-set epoxy and short bolts not rated for long-term loading; creep led to failure. |
| Design-Incompatibility | Tunnel end sections were not designed to handle hanging ceiling systems. |
| QA Oversight Lapses | Past issues with this baggage anchoring system had been noted in 1998, but were not corrected. |
Impacts Due to the Issue, Problem, or Challenge
• One fatality and one serious injury.
• Major segment of the Big Dig closed for nearly a year, excessive traffic disruption.
• Increased scrutiny of materials in tunnel applications and long‑term performance testing.
• Significant legal and public trust damage.
Corrective Actions Taken
- Replacement of epoxy anchors with long-term-rated adhesives and verified bolt specs.
- Mandatory creep testing of adhesive‑based anchor systems prior to installation.
- Independent QA review templates revised to monitor long-term stability.
Lessons Learned
• Adhesives and anchors in permanent infrastructure must meet long-term load timelines—not just installation convenience.
• Design compatibility between structural form and attachment system is essential.
• Past warning signs require responsive mitigation—and documentation.
Audit & Prevention: Project Control Questions to Ask on Future Projects to Help Control the Situation for Future Projects
Material/Adhesive Qualification
- Are fastening systems rated for expected long-term loads?
- Are vendors required to provide creep and durability test data?
Design Integration
- Are structure segments explicitly designed for the intended attachment systems?
- Are legacy systems reviewed for updated loads or design changes?
Inspection and Follow-up
- Are historical deficiency reports tracked and acted on?
- Is QA mandated to review similar structures or systems for known problems?