Case Study: Concrete Subcontractor Quality Issues Lead to Structural Repairs in Pennsylvania (2021)

Project Overview
• Name: Philadelphia Tunnel Rehabilitation
• Location: Philadelphia, Pennsylvania
• Year: 2021
• Project Size: $370 million
• Scope: Tunnel lining and concrete repairs
• Lead Agencies/Contractors: Pennsylvania DOT /

Category of the Issue, Problem, or Challenge
• Subcontractor Management
• Quality Control – Concrete

Summary of the Issue, Problem, or Challenge
Concrete subcontractor’s poor mixing and placement practices resulted in areas of honeycombing and low strength, necessitating costly repairs and delaying the tunnel rehabilitation.

Root Cause Analysis

• Inadequate batching and mixing controls.
• Insufficient supervision during concrete placement.
• Lack of proper curing and finishing procedures.
• Ineffective QC inspections and testing.

Impacts Due to the Issue, Problem, or Challenge

• Rework and repair of defective concrete sections.
• Schedule extension of 7 weeks.
• Increased labor and material expenses.
• Risk of compromised structural integrity if uncorrected.

Corrective Actions Taken

1. Enforced strict batching and mixing standards.
2. Increased onsite supervision during placement.
3. Improved curing and finishing protocols.
4. Enhanced QC testing and documentation procedures.

Lessons Learned

• Proper concrete mixing and placement are vital for structural performance.
• Continuous supervision and testing catch defects early.
• Subcontractor QC must align closely with prime contractor requirements.

Audit & Prevention: Project Control Questions to Ask on Future Projects to Help Control the Situation

• Are concrete batching and placement procedures strictly followed?
• Is onsite supervision adequate during critical operations?
• Are QC inspections frequent and well documented?