Case Study: Tunnel Liner Segment Misalignment, Big Dig (Boston, MA, 2005)
Project Overview
• Name: Central Artery/Tunnel Project (Big Dig)
• Location: Boston, Massachusetts
• Year: 2005
• Project Size: Over $14 billion total project
• Scope: Construction of underground highway tunnels; segmental concrete lining installation
• Lead Agencies/Contractors: Massachusetts Turnpike Authority /
Category of the Issue, Problem, or Challenge
• Structural Alignment
• Tunnel Segment Installation
Summary of the Issue, Problem, or Challenge
During installation of tunnel liner segments, a misalignment of several precast concrete segments occurred, leading to cracking and water leakage. The issue required partial disassembly and realignment under tight project constraints.
Root Cause Analysis
- Inaccurate Surveying: Incomplete or outdated site survey data led to misalignment during segment placement.
- Installation Tolerances: Construction tolerances were too loose, and control measures insufficient.
- Communication & Coordination: Multiple contractors working in parallel caused inconsistent installation practices.
Impacts Due to the Issue, Problem, or Challenge
- Water leakage requiring repair and waterproofing, adding costs and delays.
- Increased risk of long-term structural integrity issues.
- Public and media scrutiny due to Big Dig cost overruns and technical issues.
Corrective Actions Taken
- Improved survey and control procedures with laser scanning and real-time monitoring.
- Tighter installation tolerances and mandatory quality control checks.
- Enhanced coordination among contractors with centralized project controls.
Lessons Learned
- Precision in underground segment alignment is critical to tunnel integrity and waterproofing.
- Real-time surveying and monitoring technologies reduce installation errors.
- Clear roles and communication among contractors prevent coordination errors.
Audit & Prevention: Project Control Questions to Ask on Future Projects to Help Control the Situation
- Are high-precision surveying and monitoring technologies integrated during segment installation?
- Are installation tolerances clearly defined and enforced?
- Is contractor coordination and communication effectively managed?