Case Study: Temporary Cofferdam Failure at Chicago Riverwalk (Chicago, IL, 2017)
Project Overview
• Name: Chicago Riverwalk Extension Project
• Location: Chicago, Illinois
• Year: 2017
• Project Size: $60 million
• Scope: Construction of riverwalk structures and support piers requiring cofferdam installation
• Lead Agencies/Contractors: Chicago DOT /
Category of the Issue, Problem, or Challenge
• Temporary Structure Failure
• Water Control
Summary of the Issue, Problem, or Challenge
During excavation inside a cofferdam for pier foundation work, the temporary cofferdam structure failed due to excessive water seepage and undermining of sheet pile walls. The failure flooded the work area, halting construction and requiring emergency dewatering.
Root Cause Analysis
- Inadequate Sheet Pile Penetration: Sheet piles did not extend deep enough to prevent water inflow from riverbed sediments.
- Poor Sealing at Joints: Gaps in sheet pile joints allowed water intrusion under pressure.
- Unanticipated Hydrostatic Pressure: Water pressures from the river exceeded design assumptions.
- Lack of Real-Time Monitoring: No instrumentation was used to detect seepage before failure.
Impacts Due to the Issue, Problem, or Challenge
- Work stoppage and costly emergency pumping operations.
- Delays in foundation installation schedule.
- Increased project costs due to remediation and design revisions.
Corrective Actions Taken
- Redesign and extension of sheet piles to greater depths.
- Installation of interlocks and sealing materials to improve joint water-tightness.
- Implementation of instrumentation to monitor water pressures and seepage in real time.
- Revised risk management procedures for cofferdam construction.
Lessons Learned
- Cofferdam design must fully account for hydrostatic and seepage pressures.
- Joint sealing is critical to temporary water barrier integrity.
- Real-time monitoring can provide early warning to prevent catastrophic failures.
Audit & Prevention: Project Control Questions to Ask on Future Projects to Help Control the Situation
- Are sheet piles driven to sufficient depths to counter seepage?
- Are joint seals verified and tested for water-tightness?
- Is water pressure instrumentation installed and actively monitored during cofferdam use?