Case Study: Los Angeles Metro Purple Line Extension – Design-Build Delivery and Interface Coordination Problems (2018)

Project Overview
• Name: Los Angeles Metro Purple Line Extension
• Location: Los Angeles, California
• Year: 2018
• Project Size: $2.8 billion
• Scope: Subway tunnel and station construction using Design-Build delivery
• Lead Agencies/Contractors: Los Angeles County Metropolitan Transportation Authority (Metro), Design-Build Contractor

Category of the Issue, Problem, or Challenge
• Project Delivery Method
• Design-Build

Summary of the Issue, Problem, or Challenge
During construction, significant interface issues between tunneling subcontractors and station work contractors caused rework and delays. The Design-Build contract lacked clear interface management protocols, resulting in conflicting schedules and scope overlaps.

Root Cause Analysis

• Poorly defined scope boundaries between subcontractors.
• Lack of an integrated interface management plan.
• Inadequate communication and coordination between multiple contractors.
• Insufficient use of Building Information Modeling (BIM) for clash detection.

Impacts Due to the Issue, Problem, or Challenge
• Construction delays of 7 months.
• Cost overruns estimated at $40 million.
• Increased risks of schedule and cost impacts in remaining phases.

Corrective Actions Taken

1. Developed a comprehensive interface management plan.
2. Strengthened contractor coordination meetings and reporting.
3. Implemented BIM-based clash detection across all subcontractors.
4. Assigned a dedicated interface manager role.

Lessons Learned

• Clear scope boundaries prevent conflicts in multi-contractor projects.
• Interface management plans are essential for Design-Build projects.
• BIM facilitates early detection of spatial conflicts.
• Dedicated roles for interface coordination improve communication.

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

• Are scope boundaries clearly defined among subcontractors?
• Is there an active interface management plan in place?
• Is BIM used effectively for clash detection?
• Is a dedicated interface coordinator assigned?