Case Study: Unanticipated Peat Layers Delay Miami Canal Expansion (Florida, 2018)

Project Overview
• Name: Miami-Dade Canal Expansion Project
• Location: Miami, Florida
• Year: 2018
• Project Size: $220 million
• Scope: Canal widening and bank stabilization involving extensive earthworks
• Lead Agencies/Contractors: Miami-Dade County Public Works /

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

Summary of the Issue, Problem, or Challenge
During excavation, thick peat layers with extremely low bearing capacity were discovered, necessitating extensive ground improvement and redesign of support structures.

Root Cause Analysis

• Incomplete preliminary site investigation with inadequate borings in peat-prone zones.
• Failure to account for variable thickness and compressibility of organic soils.
• Overlooked the need for specialized foundation treatment for peat layers.
• Contract lacked explicit clauses addressing organic soil variations.

Impacts Due to the Issue, Problem, or Challenge

• Project delay of 8 months due to redesign and ground improvement using preloading and geotextiles.
• Increased costs from additional materials, labor, and extended construction duration.
• Potential long-term settlement risks if untreated peat was left in place.

Corrective Actions Taken

1. Conducted comprehensive subsurface investigations with focus on organic soil mapping.
2. Implemented ground improvement techniques including surcharging and wick drains.
3. Revised design for canal banks with reinforced foundations.
4. Included clear contract provisions to handle organic soil conditions.

Lessons Learned

• Organic soil presence requires thorough investigation and specialized treatment.
• Early identification avoids costly mid-project redesign.
• Contract language should explicitly address variable site conditions.

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

• Are peat and organic soils adequately investigated?
• Are ground improvement methods planned for soft soil zones?
• Do contracts cover changes due to organic soil variability?