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At 11:15 a.m. on May 8, Nepal time, the main tunnel of the Sunkoshi-Marin Diversion Tunnel Project in Nepal, contracted by COVEC as general contractor and jointly implemented by COVEC and China Railway No.2 Engineering Group, was successfully holed through one year ahead of schedule.

The project breakthrough celebration was grandly held in Sindhuli, Bagmati Province. Nepali Prime Minister Pushpa Kamal Dahal (Prachanda), Chinese Ambassador to Nepal Chen Song, Economic and Commercial Counselor Xie Yu, officials from relevant Nepali government departments, and representatives of COVEC and China Railway No.2 Engineering Group attended the breakthrough ceremony.

As Nepali Prime Minister Prachanda pressed the start button, the "mountain-digging marvel" — a double-shield tunnel boring machine (TBM) — began its final construction operation amid a roar. At 11:15, the TBM successfully broke through the last section of the tunnel and slowly entered the receiving shaft. The "Chinese solution" equipped with "Chinese technology" once again demonstrated well-deserved "Chinese speed" in the Himalayas.

Prime Minister Prachanda expressed warm congratulations on the tunnel breakthrough and spoke highly of the project builders. He stated that Nepal is an agriculture-based country, and how to solve irrigation water needs during the dry season is an extremely challenging problem. The successful implementation of the Sunkoshi-Marin project not only provided sufficient irrigation water for more than 120,000 hectares of farmland in Bagmati Province, promoted local agricultural development, and improved people's living standards, but also promoted economic prosperity in the areas surrounding the project.

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At the invitation of the Nepali government, Chen Song, Ambassador Extraordinary and Plenipotentiary of China to Nepal, attended the celebration ceremony. In his speech, Ambassador Chen Song said, "The contractor team of the Nepal Sunkoshi-Marin Diversion Tunnel Project has not only set multiple world records, but also actively fulfilled social responsibilities in Nepal. Our Chinese enterprises have leveraged their own advantages, contributed Chinese wisdom and Chinese solutions, and cooperated sincerely with the Nepali technical team to overcome many difficulties such as complex geology, blocked logistics, and an exceptionally long rainy season, achieving the main tunnel breakthrough one year ahead of schedule and demonstrating high-quality, high-standard Chinese speed."

Jiang Zhe, Deputy Secretary of the Party Committee and Director of COVEC (presiding over the work of the Party Committee and the Board of Directors), delivered a speech on behalf of the contractor. He stated that the Sunkoshi-Marin Diversion Tunnel Project is another "project of national pride" undertaken by COVEC in Nepal after the successful implementation of the Bheri-Babai Diversion Tunnel. Since the start of construction, COVEC Nepal Company and the project team have overcome unfavorable factors such as the pandemic and special geological environments. While ensuring tunnel safety and quality, they set multiple excavation records and ultimately achieved tunnel breakthrough one year ahead of schedule, delivering a satisfactory result to the Nepali government and people. The tunnel breakthrough is an important milestone in project construction and a new starting point for deepening cooperation. COVEC will take this opportunity to further proactively align with the needs of the Nepali government and people, and continue to jointly promote projects that advance Nepal's national economic development and enhance the well-being of the Nepali people through practical actions, making greater contributions to further strengthening China-Nepal friendship.

A water diversion project carrying hope and happiness

Nepal is rich in hydropower reserves but they are unevenly distributed, and limited by inadequate infrastructure, the effective utilization rate of water resources is extremely low. The areas of Bara, Rautahat, and Sarlahi in southeastern Nepal where the Sunkoshi-Marin Diversion Tunnel Project is located are affected year-round by dry-season drought and rainy-season flooding, making it difficult to meet agricultural irrigation needs. For a long time, how to effectively utilize water resources has been a long-cherished dream of local people. To solve this problem, Nepal's Ministry of Energy, Water Resources and Irrigation planned an inter-basin "external water diversion to internal use" project — the Nepal Sunkoshi-Marin Diversion Tunnel Project.

In 2021, leveraging its outstanding achievements in the Bheri-Babai Diversion Tunnel Project, COVEC successfully won the bid for the Sunkoshi-Marin Diversion Tunnel Project. The project aims to divert water from the water-rich Sunkoshi River to the water-scarce Marin River through a 13.3 km TBM diversion tunnel, providing agricultural irrigation water for 122,000 hectares of land in Bara, Rautahat, Sarlahi, and other areas downstream of the Marin River. The head difference generated by the diversion can also provide the local area with 28.62 MW of clean hydropower energy, which can not only bring significant economic and social benefits to the region, but also reduce desertification of farmland, and is extremely important for promoting ecological restoration and social development in the region.

Chinese solutions overcome new challenges of the Kathmandu Nappe

The Nepal Sunkoshi-Marin Diversion Tunnel is the world's first double-shield TBM tunnel to pass through the "Siwalik + Kathmandu Nappe" strata. According to the project builders, the Siwalik strata of the Himalayas are sometimes soft and sometimes hard, "like tofu and also like iron," while the geological structure of the Kathmandu Nappe contains an extremely complex distribution of sedimentary, magmatic, and metamorphic rocks. To ensure the safe and smooth breakthrough of the tunnel, the project team advanced construction and production in an orderly manner through measures such as building a complete self-operated "micro supply chain," targeted design of TBM equipment, independent equipment installation and maintenance, and implementation of comprehensive self-operation. It took only 13 months to complete key processes including overall project design, equipment installation and commissioning, TBM refurbishment, key civil works, and segment pre-production. The TBM was successfully launched two months ahead of schedule and overcame adverse geological challenges such as high overburden, high geothermal heat, high ground stress, high water seepage, uneven hardness, geological fault zones, and large deformation of soft rock. The TBM successfully passed through two sections of large water inflow, three fractured fault zones, nearly 4 km of high-overburden rockburst areas, and a 500-meter soft-rock large-deformation zone.

Naran Baral, Minister of Labor of the project, said, "I had never seen a TBM in real life before. This time I had the opportunity to see this big machine with my own eyes and enter a TBM tunnel for the first time. It was a very shocking and unforgettable experience for me. The Chinese team is excellent. They are skilled in TBM technology and have rich experience and construction track records in large-scale infrastructure construction, which is impressive. I am very happy to work here, and being a member of this team is a very valuable experience for me."

Challenging ourselves: Chinese technology repeatedly breaks excavation records

Unpredictable geology, combined with many unfavorable factors such as blocked logistics and an exceptionally long rainy season, undoubtedly placed higher demands on the project's construction organization and safety control.

To maximize construction production efficiency and project quality and achieve tunnel breakthrough as early as possible, the project team repeatedly optimized and innovated processes and refined the process cycle to the extreme, successfully reducing the time consumed by a single excavation process cycle from an average of 45 minutes to an average of 24 minutes, with the fastest single cycle improved to 17 minutes. Monthly tunnel excavation continuously broke new records: from an initial monthly advance of 600 meters to 1,000 meters, 1,100 meters, 1,200 meters, 1,300 meters, 1,500 meters... It set a world record of completing 500 meters of trial excavation within 30 days, achieved industry-leading results of a maximum single-day advance of 72.68 meters and a maximum single-month advance of 1,503.3 meters, and ranked among the world's leading levels with a production speed of 721 meters per month. The excellent progress achieved by the project was commended six times in letters from the Nepali government, and Nepali dignitaries and industry researchers visited the project site eight times for study and inspection.

Local employees said in interviews that Nepal's geological conditions are extremely complex. Before the Bheri-Babai and Sunkoshi-Marin tunnels, tunnel construction had always been a very slow process, usually requiring three to four years to complete a 5-kilometer tunnel, and TBM technology was unheard of in Nepal. But now, this technology has become a household name in Nepal. Our project completed this 13.3-kilometer tunnel in only 18.5 months, which can be said to have brought great convenience to Nepal's tunnel construction field. This is very meaningful.

China-Nepal cooperation: creating a new model of mutual benefit and win-win

During construction, the project team actively fulfilled social responsibilities and upheld the principle of benefiting others before benefiting oneself. It participated in three local road traffic accident rescues, donated about 2,000 m3 of sand and gravel aggregate and 60 sets of schoolbags and teaching aids to local schools and the Red Cross Foundation, helped surrounding villages clear 10 kilometers of irrigation canals, provided more than 2,000 person-times of employment opportunities to local villagers, and trained more than 260 local technical talents in total, including maintenance workers, electricians, gantry crane and forklift operators, gaining high recognition from the Nepali government and people.

Project translators Narendra Bahadur Sunar (Mazda) and Top Bahadur Pandey (Little Watermelon), assistant to the civil engineering department manager, both followed the project team from Bheri-Babai to the Sunkoshi-Marin project.

When asked about what they had gained from working for a Chinese enterprise, Mazda said, "When I first started working on the Bheri-Babai project, I was just a rebar worker. Because I knew a little Chinese, they asked me to be a translator. By helping them translate and communicate, my Chinese improved. When they asked me whether I wanted to come work on the Sunkoshi-Marin project, I agreed quickly. Here, I learned skills in project construction and personnel management. Now my income has increased. I built a new house for my family and bought a car, and I can also support my two children's schooling. I am very happy that the project has been successfully holed through, and I want to continue working for the Chinese company!"

Little Watermelon said that he has worked with Chinese colleagues for more than six years. His Chinese colleagues have taught him many things and also helped him increase his income. When there is something he does not understand or cannot do at work, his Chinese colleagues tell him how to do it, such as how to use an excavator, how to arrange work, and how many people to assign.

Dinesh Ghimire, Minister of the Project Contract Department, said that the project has provided local residents with a large number of employment and business opportunities, and has greatly promoted regional economic development through local recruitment and the procurement of machinery, equipment, and raw materials. Local people's mindsets are also gradually changing: participating personally in a large-scale engineering project is very meaningful. They can not only learn a lot, but also come into contact with and benefit from more people with different knowledge or skills, which is more important than obtaining economic gains.