Strategies for achieving sustainable infrastructure through lean construction optimization in the Indonesia Dam Project

Dams are critical infrastructure that support water security, energy production, food resilience, and disaster risk reduction in Indonesia's rapidly developing regions. However, conventional delivery of dam projects still suffers from delays, cost overruns, and waste arising from fragmented planning and low workflow reliability. This study investigates how Lean Construction, particularly the Last Planner System (LPS) integrated with Building Information Modeling (BIM), can enhance performance in the Tiga Dihaji Dam Project Package 4. An explanatory sequential mixed-methods design was adopted, combining document review, site observations, and structured discussions with project stakeholders, followed by quantitative evaluation of schedule and productivity indicators. The results show that collaborative planning, weekly coordination, constraint removal, and visual control through BIM support more reliable task commitments, reduce rework and waiting, and improve information flow. Lean implementation also decreased non-value-adding activities such as overproduction, excessive inventory, and unnecessary material handling on site. Overall, Lean-LPS implementation contributed to measurable performance gains, including significant schedule acceleration (Ra ≈ 96.7%; Ri ≈ 97.2%), while reinforcing sustainable infrastructure outcomes, organisational learning, and alignment with national dam development policies and Sustainable Development Goals targets. The findings provide practical guidance for scaling Lean practices to other Indonesian dam projects and large infrastructure programs.