1. Preparatory Phase and Site Rehabilitation
The history of Rogun dates back to the late Soviet era, but decades of political changes and floods left the site heavily compromised. The modern construction phase, led by the Italian engineering firm Webuild (formerly Salini Impregilo) alongside international consultants, began with massive rehabilitation works.
- Dewatering and Clearing: Millions of cubic meters of water and debris had to be pumped out of tunnels that were flooded in the 1990s.
- Infrastructure Layout: Before the dam could rise, engineers built hundreds of kilometers of access roads, concrete batching plants, crushing plants, and residential camps for thousands of workers in a remote, mountainous terrain.
2. River Diversion: The Critical Milestone
In October 2016, construction reached its first major milestone: the diversion of the raging Vakhsh River.
- The Process: Using a fleet of heavy dump trucks, workers blocked the natural riverbed in a matter of hours, forcing the water into two massive, pre-excavated concrete-lined diversion tunnels.
- Significance: This successfully dried out the foundation area, allowing workers to begin the construction of the main dam structure in a dry environment.
3. Building the World’s Tallest Embankment Dam
The core of the Rogun project is a 335-meter-high rock-fill dam with a clay core. Choosing a rock-fill design over pure concrete was essential to give the structure flexibility against seismic activity.
- The Clay Core: The central impervious core is made of highly compacted clay, which prevents water from seeping through the dam.
- Layered Shells: On either side of the core, layers of filter materials and heavy rock-fill are meticulously placed and compacted to provide structural stability.
- Volume: The dam will ultimately require over 70 million cubic meters of material, transported and compacted around the clock.
4. The Underground Marvel: Powerhouse and Tunnels
What makes Rogun unique is that a massive portion of the project is entirely invisible from the surface. The site features an intricate underground network of tunnels, shafts, and chambers spanning over 70 kilometers.
- The Powerhouse Cavern: Engineers excavated a massive subterranean chamber (measured at roughly 70 meters high and 220 meters long) to house the turbines and generators.
- Hydraulic Tunnels: These include specialized transport tunnels, water intake shafts, penstocks, and tailrace tunnels to guide water to and from the turbines.
- Geological Consolidation: Because the mountain consists of complex rock formations and salt layers, millions of rock bolts, anchors, and thousands of tons of shotcrete (sprayed concrete) were used to stabilize the underground caverns.
5. Phased Power Generation (Early Monetization)
Waiting for a 335-meter dam to be fully completed before generating power is financially unviable. Therefore, the construction strategy utilized a phased commissioning approach.
- Stage One Dam: A temporary, lower-height coffer dam was built within the main structure to allow early reservoir impounding.
- First Turbines: This partial reservoir provided enough water head to launch Unit 6 in 2018, followed by Unit 5 in 2019.
- The Strategy: The electricity generated by these early units is sold to fund the ongoing construction of the remaining height of the dam and the installation of the four remaining turbines (totaling 6 units with a 3,600 MW capacity).
6. Managing the Salt Dome Challenge
One of the most complex geological hazards at the Rogun site is the presence of an underground salt wedge (ion-rich salt layer) right beneath the reservoir area.
- The Risk: If water contacts this salt layer, it could dissolve it, compromising the stability of the dam’s foundation.
- The Solution: Engineers designed a highly sophisticated hydraulic barrier. This involves continuous grouting (injecting a special cement mix into the rock) and a specialized drainage system that intercepts water, preventing it from dissolving the salt formations.
Conclusion
The construction of the Rogun Hydropower Plant is a masterclass in modern heavy civil engineering. By combining colossal surface earthworks with delicate underground excavation and advanced geological risk management, the project showcases how human ingenuity can harness nature in the most unforgiving environments. When the final stone is placed and the last turbine spins, Rogun will stand as a monument to engineering resilience.