Case Study: Poor Quality Work by Subcontractor Causes Rework on Dam Spillway in Washington (2017)

Project Overview
• Name: Grand Coulee Dam Spillway Repair
• Location: Washington State
• Year: 2017
• Project Size: $210 million
• Scope: Spillway concrete repairs and reinforcement
• Lead Agencies/Contractors: U.S. Bureau of Reclamation /

Category of the Issue, Problem, or Challenge
• Subcontractor Management
• Quality Control

Summary of the Issue, Problem, or Challenge
Subcontractor’s inadequate workmanship in concrete placement led to cracks and honeycombing, requiring costly rework and delay.

Root Cause Analysis

  • Subcontractor’s QC procedures were insufficient and poorly enforced.
  • Prime contractor did not conduct enough oversight during concrete pours.
  • Lack of skilled labor and inadequate training for subcontractor crews.
  • Failure to follow mix design and curing protocols.

Impacts Due to the Issue, Problem, or Challenge

  • Rework delayed spillway repair by 2.5 months.
  • Additional costs for material, labor, and inspection.
  • Risk to dam safety if defects had gone undetected.

Corrective Actions Taken

  1. Increased prime contractor QC staff and inspection frequency.
  2. Required subcontractor re-training and certification for concrete crews.
  3. Implemented stricter mix design controls and curing monitoring.
  4. Engaged third-party quality assurance auditors.

Lessons Learned

  • Subcontractor quality control is critical for safety-critical infrastructure.
  • Prime contractors must enforce QC standards continuously, not just spot checks.
  • Skilled labor and training directly affect quality outcomes.

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

  • Are subcontractors’ QC plans reviewed and approved before work?
  • How is subcontractor quality monitored during execution?
  • Are crews adequately trained and certified for specialized work?
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