Dayu Xuedun, the second tunnel boring machine custom-built in China for the Polihali Transfer Tunnel, a key component of Phase II of the Lesotho Highlands Water Project, was launched into operation on Monday.

by Xinhua writers Hang Zebo and Bai Ge

MASERU, April 23 (Xinhua) -- In early autumn, the highlands of Lesotho still simmer beneath a relentless midday sun. In the mountainous Mokhotlong district, east of the capital Maseru, roads wind through peaks rising more than 2,000 meters above sea level. Halfway up a slope, deep inside a tunnel carved through solid rock, a 425-meter-long tunnel boring machine (TBM) is hard at work, its steady roar echoing through the mountain.

Named Dayu Xuedun, the machine was launched into operation on Monday. It is the second TBM custom-built in China for the Polihali Transfer Tunnel, a key component of Phase II of the Lesotho Highlands Water Project.

About 34 km away, at the tunnel's far outlet, its twin, Dayu Changfeng, has been grinding steadily through rock for more than a year. Together, the two machines form the mechanical backbone of the project.

A landlocked country in southern Africa, Lesotho is defined by its rugged terrain, with roughly three-quarters of its eastern territory covered by mountains. Rich in water resources, the country plays a pivotal role in the region's cross-border infrastructure schemes. The LHWP is designed to channel water from Lesotho's highlands to water-scarce regions of neighboring South Africa.

Led by Chinese firm Yellow River Co., Ltd. and implemented jointly with Sinohydro Bureau 3, the Polihali Transfer Tunnel project is widely seen as a world-class hydraulic engineering challenge because of its harsh construction environment and high technical demands.

The tunnel passes through hard rock, deep cover, and complex geological conditions. To handle these conditions, the two TBMs are equipped with heavy-duty cutterheads, forward-probing drill systems, and other China-developed technologies to improve safety and efficiency.

Weighing about 1,500 tonnes, with a cutterhead diameter of 5.35 meters, Dayu Xuedun was manufactured and tested in China before being dismantled into 126 components. It was shipped by sea to Durban Port in South Africa and transported overland to the project site over two months.

With limited space outside the tunnel, builders then moved and assembled it section by section inside the mountain over more than four months.

The greater test lies underground, where the two TBMs must meet in the middle of the 34-km tunnel with breakthrough error controlled to within millimeters.

"Even the slightest deviation is unacceptable," said Zhen Qian, deputy chief engineer of the project.

The project is also deploying advanced technologies such as two-component grouting, in which cement slurry and sodium silicate are injected between the tunnel lining segments and surrounding rock to improve tunnel stability and construction efficiency.

For workers inside the tunnel, these technical challenges are matched by harsh conditions. Zhao Xusheng, production manager of the project, said temperatures can reach 40 degrees Celsius when the TBM is in operation.

"Our clothes get soaked, then dry, and then get soaked again," Zhao said, adding that the team remains focused on delivering the project to a high standard.

Beyond engineering, the project is reshaping local livelihoods. The transfer tunnel project has created more than 2,000 local jobs and launched skills training in areas such as first aid, concrete work, and plumbing, with a target of training 3,500 skilled workers.

Among them is 26-year-old Manaha Naha. When she joined the project in 2023, she worked as a cleaner. After receiving training, she now manages the lamp room.

"The project gave me skills and changed my life," she said. "My family has raised cattle and sheep for generations. After finding a job here, I can now support my family and even help pay school fees for my sister's child."

Naha said many nearby families had benefited from the project through jobs, annual distributions of food and daily necessities, and improved local facilities.

Since 2023, the project has built roads and renovated a football ground and a clinic, with more community facilities such as public toilets, a daycare center, and standardized stalls for small vendors planned for 2026.

Environmental protection has also been a priority. Given Lesotho's fragile ecosystem, the project has installed wastewater treatment systems and introduced third-party monitoring to ensure compliant discharge or reuse. Contaminated soil from oil leaks is promptly treated and later restored through hydroseeding.

"We want to leave the place in the same condition as when we arrived," said Wang Yong, the project's safety director.

At the launch ceremony, Chinese Ambassador to Lesotho Yang Xiaokun said the project is an important outcome of cooperation between Lesotho and South Africa, as well as between China and Lesotho. He described it as not only a major infrastructure undertaking, but also a key driver of livelihoods and economic growth.

Lesotho's Minister of Natural Resources Mohlomi Moleko thanked all parties involved for their contribution to economic development, job creation, business support, and livelihood improvement, saying the project also underscored deepening regional cooperation between South Africa and Lesotho.

Once the second phase is completed, Lesotho's annual water transfer capacity to South Africa will increase from 780 million cubic meters to 1.27 billion cubic meters, while the country's hydropower generation is also expected to rise. Under the bilateral agreement, the project will help ease water shortages in five South African provinces, while generating revenue for Lesotho.

"The hopes of the builders are embedded in the names of the two machines themselves -- Changfeng, a sharp blade to cut through mountains, and Xuedun, a shield to stand the test of time," Zhao said.