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  • Inaccurate Surveying: Incomplete or outdated site survey data led to misalignment during segment placement.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

  1. Improved survey and control procedures with laser scanning and real-time monitoring.
  2. Tighter installation tolerances and mandatory quality control checks.
  3. 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?
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