Located amid the lowland and mountain terrain of Nganjuk in East Java, the Semantok Dam aims to reduce flood discharge, ensure water availability, and nearly triple the district’s agricultural productivity. When designing the project, PT Hutama Karya soon discovered that the sandy soil layer presented a significant obstacle to building a dam in the region. Using reality modeling and construction simulation, they determined how to alter the design to prevent leaks and eliminate the need for carbon-intensive excavation of fill material off site. The finished dam now guards against flooding, supports agriculture, and bolsters economic development.