On the occasion of International Workers' Day, with the last successful blast, the Chenxi Pumped Storage Power Station in Hunan Province has once again reported good news—the diversion tunnel and spillway tunnel of the lower reservoir have achieved full breakthrough, laying a solid foundation for the acceptance of the lower reservoir closure stage.

The diversion tunnel and spillway tunnel of the lower reservoir are permanent-temporary combined structures of the lower reservoir hub project. In the early stage, they serve as diversion structures, and in the later stage, after partial plugging and modification, they serve as water release structures. They consist of a diversion tunnel and a vertical-shaft spillway tunnel respectively, arranged within the mountain on the right bank of the lower reservoir dam. The total tunnel length is 333.33 m, with a clear cross-section size of 3.5 m (width) × 4.5 m (height), adopting a gate-shaped structural design. The maximum discharge flow is 82.13 m3/s. They undertake the dual mission of diversion and flood control during the construction period and regulating the water level of the lower reservoir during the operation period, and are crucial to ensuring the stable operation of the power station and safe flood passage during the flood season.

The diversion tunnel and spillway tunnel of the lower reservoir have shallow burial depth. Facing multiple pressures including complex geological structures with Class IV and V surrounding rock accounting for approximately 88% and a tight schedule for closure acceptance, the project team ensured safe and efficient advancement of tunnel construction through scientific construction methods and rigorous process management, ultimately successfully achieving the breakthrough goal.

The smooth breakthrough of the diversion tunnel and spillway tunnel of the lower reservoir not only marks that the lower reservoir project has officially entered the countdown to closure, but is also of great significance for promoting the comprehensive acceleration of subsequent main works of the lower reservoir. Next, the project team will focus on the 2025 project closure goal, build on the momentum, and run out the "acceleration" for fully building a clean energy project in the western Hunan region of Hunan Province.

The Chenxi Pumped Storage Power Station in Hunan Province is a key implementation project of the 14th Five-Year Plan of Hunan Province, with a total installed capacity of 1.2 million kilowatts and a total investment of 7.865 billion yuan. It installs four reversible hydro-generator units with a single-unit capacity of 300,000 kilowatts, and consists of an upper reservoir, a lower reservoir, a water conveyance system, an underground powerhouse, and a ground switch station. After the power station is completed, it is expected to generate an average annual power output of 1.277 billion kWh, save 452,000 tons of standard coal per year, and reduce carbon dioxide emissions by 960,000 tons. It is of great significance for the clean energy transition of Hunan Province, ensuring the stable operation of the power grid, and promoting the sustainable development of the local economy.

The spillway tunnel of the Chenxi Pumped Storage Power Station in Hunan Province has been successfully breakthrough