Case Study: Landslide During Highway Construction on I-70 (Colorado, 2015)

Project Overview
• Name: I-70 Mountain Corridor Improvements
• Location: Glenwood Canyon, Colorado
• Year: 2015
• Project Size: Multi-million-dollar highway widening and stabilization project
• Scope: Excavation and slope work adjacent to highway embankments
• Lead Agencies/Contractors: Colorado DOT /

Category of the Issue, Problem, or Challenge
• Geotechnical Failure
• Slope Stability

Summary of the Issue, Problem, or Challenge
Heavy rains caused a large slope failure adjacent to the highway embankment during excavation work. The landslide partially buried construction equipment and blocked the highway, leading to emergency response and slope stabilization.

Root Cause Analysis

• Saturated Soils: Unusually heavy precipitation saturated slope soils beyond design assumptions.
• Inadequate Drainage: Temporary drainage systems failed to divert water adequately.
• Excavation Oversteepening: Cuts into slope exceeded safe angles without sufficient reinforcement.
• Lack of Real-Time Slope Monitoring: No instrumentation to detect ground movement before failure.

Impacts Due to the Issue, Problem, or Challenge

• Highway closure and major traffic disruption.
• Equipment damage and worker safety risk.
• Increased project costs and schedule delays.

Corrective Actions Taken

1. Installation of soil nails, retaining walls, and reinforced shotcrete to stabilize slopes.
2. Upgrading drainage systems to handle extreme precipitation events.
3. Implementation of real-time slope monitoring instrumentation.
4. Revised slope excavation plans with conservative angles and staging.

Lessons Learned

• Geotechnical designs must anticipate extreme weather events.
• Temporary drainage and slope support must be robust and redundant.
• Early detection of slope movement can prevent catastrophic failure.

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

• Are temporary drainage systems designed for extreme weather scenarios?
• Are slopes instrumented and monitored continuously during excavation?
• Are excavation plans regularly reviewed against geotechnical and weather data?