Drivers and Impacts of Frequent Contract Amendments in SUTT Projects: Evidence on Cost and Time Performance

Frequent contract amendments have become a recurring phenomenon in Saluran Udara Tegangan Tinggi (SUTT/High-Voltage Overhead Transmission Line) infrastructure projects in Indonesia. While contract modifications are often necessary to accommodate uncertainties, excessive amendments indicate systemic vulnerabilities in project governance and risk allocation. This study investigates the key drivers behind repeated contract amendments in SUTT projects and quantifies their direct impacts on cost and schedule performance. This research adopts a mixed-method approach, combining qualitative interpretation and quantitative analysis of empirical historical data from three major SUTT projects in Indonesia. To identify the root causes, a thematic content analysis was performed on the comprehensive contract history logs, categorizing the drivers into five interlocking factors: chronic land acquisition and social conflicts, unforeseen geotechnical conditions and redesigns, supply chain interdependencies, regulatory bottlenecks, and procurement strategy shifts. The findings reveal that these repetitive amendments trigger severe performance deviations. The cumulative impact of these modifications resulted in massive cost overruns, with two out of the three analyzed projects exceeding 100% of their initial budgets, driven by massive structural Variation Orders (VOs) and external contract consolidations. Concurrently, schedule performance suffered substantial delays, resulting in a duration overlap of 371 to 484 days beyond the original baseline. This research contributes to construction management literature by providing rigorous, quantifiable empirical evidence on the destructive link between contract dynamics and project performance. In practice, it offers a strategic framework for policymakers and utility stakeholders to shift toward advanced geotechnical pre-investment, proactive land-clearing governance, and the implementation of adaptive yet tightly bounded contract design methods to mitigate excessive amendments and safeguard the efficiency of public infrastructure investment.