Case Study: Unexpected Sinkhole Formation Delays Roadway Construction in Louisiana (2016)

Project Overview
• Name: Louisiana Highway 90 Reconstruction
• Location: Lafourche Parish, Louisiana
• Year: 2016
• Project Size: $150 million
• Scope: Roadway reconstruction with extensive embankment and drainage improvements
• Lead Agencies/Contractors: Louisiana DOTD /

Category of the Issue, Problem, or Challenge
• Geotechnical
• Differing Site Conditions

Summary of the Issue, Problem, or Challenge
During excavation, an unexpected sinkhole developed due to underlying karst geology, causing ground instability and halting construction.

Root Cause Analysis

• Inadequate geotechnical investigation in karst-prone area.
• Lack of detailed subsurface mapping and ground-penetrating radar (GPR) surveys.
• Underestimation of dissolution features in limestone bedrock.
• No contingency plans for sudden ground collapse.

Impacts Due to the Issue, Problem, or Challenge

• Construction halt for 3 months while ground stabilization took place.
• Additional costs for sinkhole remediation and redesign of embankment support.
• Safety risks for workers and equipment near unstable ground.

Corrective Actions Taken

1. Performed detailed geophysical surveys to map subsurface voids.
2. Installed grouting and underpinning to stabilize affected zones.
3. Revised construction approach to avoid high-risk areas.
4. Updated risk management protocols for karst terrain.

Lessons Learned

• Karst terrains require specialized investigations including GPR and borehole imaging.
• Early identification and monitoring prevent hazardous incidents.
• Construction plans must include karst risk mitigation strategies.

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

• Has karst risk been assessed through advanced geotechnical methods?
• Are contingency and monitoring plans in place for ground collapse?
• Are workers trained to recognize and respond to sinkhole hazards?