Case Study: Quality Control Deficiency in Dewatering Operations on Houston Subway Project (Texas, 2020)

Project Overview
• Name: Houston Metro Rail Expansion
• Location: Houston, Texas
• Year: 2020
• Project Size: $1.1 billion
• Scope: Excavation and dewatering for tunnel construction
• Lead Agencies/Contractors: Metropolitan Transit Authority of Harris County /

Category of the Issue, Problem, or Challenge
• Geotechnical
• Quality Control

Summary of the Issue, Problem, or Challenge
Poor monitoring and control of groundwater levels during dewatering led to soil instability and excavation collapse risk.

Root Cause Analysis

• Insufficient groundwater monitoring instrumentation and data analysis.
• Lack of established water level control thresholds and emergency response plans.
• Inadequate training of dewatering operators and field engineers.
• Poor communication between geotechnical and construction teams.

Impacts Due to the Issue, Problem, or Challenge

• Project delay of 3 months due to stabilization works and redesign of dewatering system.
• Additional costs for instrumentation, labor, and redesign.
• Safety risks for workers due to unstable excavation.

Corrective Actions Taken

1. Installed additional groundwater monitoring wells with real-time data transmission.
2. Developed water level control plans with defined thresholds and contingency measures.
3. Conducted training sessions on dewatering and groundwater control.
4. Improved communication protocols between geotechnical and construction teams.

Lessons Learned

• Continuous groundwater monitoring is essential during deep excavations.
• Clear control plans and thresholds prevent instability.
• Training and communication enhance safety and quality.

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

• Is groundwater monitored continuously with reliable instrumentation?
• Are control thresholds and emergency plans in place?
• Are operators and engineers trained on dewatering QC?