Case Study: Unexpected Flooded Soils Disrupt Bridge Pier Construction in Mississippi (2019)
Project Overview
• Name: Mississippi River Bridge Replacement
• Location: Vicksburg, Mississippi
• Year: 2019
• Project Size: $280 million
• Scope: Replacement of major river bridge with deep pier foundations
• Lead Agencies/Contractors: Mississippi Department of Transportation (MDOT) /
Category of the Issue, Problem, or Challenge
• Geotechnical
• Differing Site Conditions
Summary of the Issue, Problem, or Challenge
High groundwater levels and flooded soils encountered during excavation caused equipment difficulties and foundation instability, requiring redesign and additional dewatering.
Root Cause Analysis
- Insufficient assessment of seasonal groundwater fluctuations in preliminary studies.
- Underestimation of floodplain soil conditions.
- Lack of real-time groundwater monitoring during construction.
- Contract provisions did not fully allocate risks of fluctuating water conditions.
Impacts Due to the Issue, Problem, or Challenge
- Delay of 5 months due to installation of dewatering wells and redesign of excavation support.
- Increased costs related to pumping, equipment downtime, and soil stabilization.
- Safety risks associated with unstable excavations and working in flooded conditions.
Corrective Actions Taken
- Implemented comprehensive groundwater monitoring and data collection.
- Designed and installed robust dewatering systems with redundancy.
- Revised foundation excavation methods for saturated soils.
- Updated contractual risk sharing related to water condition variability.
Lessons Learned
- Groundwater and floodplain conditions must be thoroughly understood before deep excavations.
- Real-time monitoring allows proactive management of water-related risks.
- Clear contract language prevents disputes over water condition impacts.
Audit & Prevention: Project Control Questions to Ask on Future Projects to Help Control the Situation
- Are groundwater studies sufficiently detailed and ongoing?
- Is dewatering equipment planned with capacity and redundancy?
- Are contracts clear on water-related risks and mitigation responsibilities?