Portuguese 
Spanish 
Simultaneous tunnel breakthroughs in the Himalayas accelerated one of India’s most ambitious hydroelectric projects and increased attention on a project that combines large-scale power generation, flood control, underground engineering, and construction in a remote area with complex terrain.
The construction of the Dibang Multipurpose Project advanced to a decisive stage in the state of Arunachal Pradesh, in northeastern India, after Larsen & Toubro reported the simultaneous breakthroughs of diversion tunnels DT-4 and DT-5 on April 28, 2026.
In the Lower Dibang Valley, the milestone reinforced the progress of a 2,880 MW hydroelectric plant, designed by NHPC with a 278-meter concrete-gravity dam and a strategic role in expanding India’s energy infrastructure.
Diversion tunnels accelerate work in the Dibang Valley
Temporary structures, the diversion tunnels allow the river to be channeled through excavated galleries while teams work on critical areas of the riverbed and foundations, an indispensable step in large-scale hydroelectric projects.
-
India Deploys High-Speed Lifesaving Drone in Bay of Bengal Rescue Operations
-
Hong Kong Converts Former Coastal Landfill into Desalination Plant Producing 135 Million Liters of Drinking Water Daily
-
At 35, Janaína paused her law studies to return to truck driving, later hauling up to 28 tons across Brazil
-
Twin Earthquakes of Magnitude 7.2 and 7.5 Strike Venezuela, Leaving Over 1,400 Dead and Affecting Millions, Potential Losses Estimated at $6.7 Billion
In the case of Dibang, the completion of both breakthroughs on the same day reduced one of the most significant technical barriers before the consolidation of the main dam and opened up space for new execution fronts.
Adding this progress to DT-3, completed in February 2026, three of the five diversion tunnels planned for the project have already been completed, indicating progress in an essential underground phase of the project.
This front is part of the so-called Lot 02, consisting of 37 kilometers of access roads, two permanent bridges, and five diversion tunnels, which together total 6.4 kilometers in length on the site.
In a mountainous and challenging region, underground excavation requires geological control, ventilation, drainage, and continuous monitoring, because any instability can affect the safety of the teams and the pace of interventions.
According to Equipment India, Larsen & Toubro attributed the progress to the coordination of two opening blasts on the same day, carried out under geologically and environmentally complex conditions in the Lower Dibang Valley.
2,880 MW Hydroelectric Plant Will Have Functions Beyond Generation
According to NHPC data, the Dibang Multipurpose Project is located on the Dibang River, in the Lower Dibang Valley district, near the village of Munli and about 43 kilometers from Roing.
The Indian state company classifies the project as a hydroelectric generation structure associated with flood control, with a dam positioned approximately 1.5 kilometers above the confluence of the Ashu Pani and Dibang rivers.
Designed for 2,880 MW, the plant will have 12 generating units of 240 MW each, installed in an underground powerhouse, a configuration that reinforces the technical dimension of the project in the eastern Himalayas.
The project energy reported by NHPC is 11,223 million units per year, while the estimated cost is 31,876.39 crore rupees, based on May 2021 prices.
In addition to electricity generation, the plant was designed to moderate downstream floods of the dam throughout the monsoon period, up to a limit of 3,000 cumecs, according to NHPC’s official page.
This design expands the role of the work, as the structure ceases to be just an energy supply asset and becomes part of water management in a strategic basin of northeastern India.
278-meter dam expands project scale
In the technical design released by NHPC, the main dam will be 278 meters high and will be of the concrete-gravity type, a characteristic that places the project among the most ambitious hydroelectric works under construction in the country.
In a hydroelectric plant, this height helps create the hydraulic head used to move the turbines, especially when combined with high flow, multiple generating units, and conduits designed for a high volume of water.
To carry the water to the powerhouse, the system planned by the state company includes six intake tunnels, each with a diameter of 9 meters and a length between 300 and 600 meters.
The configuration shows the underground dimension of the work, which depends not only on the visible dam but also on galleries, accesses, and internal structures capable of safely conducting high volumes of water.
The location of the construction site also weighs on the project, as NHPC indicates that the nearest railway access is in Tinsukia, 153 kilometers away, and the nearest airport is in Dibrugarh, 198 kilometers away.
This distance highlights the importance of logistics to transport equipment, concrete, steel, and technical teams to an area of rugged terrain, where the progress of the works depends on the integration between accesses, tunnels, and civil fronts.
Hydroelectric schedule depends on new stages
The construction has an official deadline of nine years from the approval of the Economic Affairs Committee of the Indian government’s Cabinet, recorded by NHPC on February 27, 2023.
In projects of this size, the execution cycle is usually long because it involves deep foundations, underground excavations, large volumes of concrete, electromechanical assembly, and permanent adaptation to the geological conditions of the terrain.
Before any commercial generation, it will still be necessary to advance in access, driving systems, dam concreting, assembly of generating units, and integration of the underground powerhouse with the operational set.
For this reason, the breakthrough of tunnels DT-4 and DT-5 does not represent the completion of the work, but signals that an essential preparatory stage gained traction throughout 2026.
The interest around Dibang comes from the combination of scale, location, and purpose, as India builds, in a valley far from major industrial centers, a project of great energy capacity and a strong component of heavy engineering.
Amid rugged terrain, long logistics, and challenging climate, the continuity of the project will depend on the ability to keep civil fronts in operation and sustain the advancement of structures that still need to be completed.
With three diversion tunnels already broken through and the 278-meter dam planned in the official design, Dibang remains one of India’s main bets in large-scale hydroelectric infrastructure.
