Editor's Note: On June 16, the Shenzhen-Zhongshan Link passed its completion acceptance inspection. Since the 18th National Congress of the Communist Party of China, a series of major projects have achieved new breakthroughs, boosting high-quality economic and social development and helping to realize the people's aspiration for a better life. At the same time, the siting and construction of major projects are closely related to the local natural conditions and ecological environment. How to properly handle the relationship between development and protection, utilization and restoration—engineering builders have actively explored this.

　　Viewing the design, construction, and operation and maintenance processes of major projects from an ecological perspective, to understand how engineering builders adhere to a systematic approach, promote harmonious coexistence, and lay a solid green foundation for high-quality development.

　　“Look! It's a white dolphin!”

　　At the curtain wall construction site of the main building on the west artificial island of the Shenzhen-Zhongshan Link, a sudden cry of surprise rang out. Looking closely, on the Lingdingyang estuary, small pods of Chinese white dolphins could be faintly seen, now disappearing into the sea, now surfacing, forming a delightful contrast with the Shenzhen-Zhongshan Link beside them.

　　“A super project should be a ‘green pacesetter.’” Xu Guoping, chief person in charge of island and tunnel design for the Shenzhen-Zhongshan Link at CCCC Highway Consultants Co., Ltd., said that from the very beginning of the design of the Shenzhen-Zhongshan Link, the concept of ecological protection was integrated into construction, vessel shipping, and environmental supervision, and through technological innovation, process innovation, and management innovation, the Chinese white dolphin—a national first-class key protected wild animal—has been better safeguarded.

　　Efficient construction—

　　Setting a new record for rapid island formation and reducing the impact of construction on the white dolphin nature reserve

　　In the Pearl River Estuary Chinese White Dolphin *** Nature Reserve, covering an area of about 460 square kilometers, numerous white dolphins are active.

　　On the Lingdingyang estuary, the Shenzhen-Zhongshan Link spans the east and west banks of the Pearl River. It is another cross-sea cluster project in China, after the Hong Kong-Zhuhai-Macao Bridge, integrating “bridge, island, tunnel, and underwater interchange” into one.

　　When engineering construction meets white dolphin protection, the scale of the challenge is imaginable.

　　“Building such a massive project in the migration area of the Chinese white dolphin requires extreme caution; the slightest mistake could cause irreversible impacts,” said Yue Yuanzheng, general manager of the Shenzhen-Zhongshan Link project department of CCCC ** Harbor Engineering Co., Ltd. “We must minimize the impact.”

　　Viewed from above, a huge artificial island looks like a roc spreading its wings ready to fly—this is the west artificial island, the advance project of the Shenzhen-Zhongshan Link.

　　“Building an island of about 137,000 square meters—equivalent to 19 standard football fields—on the vast sea, if traditional construction methods were used, the construction period would be long and would disturb the white dolphins' living environment,” said Liu Haobin, deputy general manager of the Shenzhen-Zhongshan Link project department of CCCC ** Harbor Engineering Co., Ltd. The construction team independently developed a 12-hammer linked hydraulic vibratory hammer unit, and in only four and a half months successfully drove 57 giant steel cylinders into the seabed rock layer, setting a world record for rapid island formation while effectively reducing the impact of offshore construction on the marine environment and the white dolphins.

　　Over the seven-year construction period, protecting the white dolphins was both a “sprint” and a “relay race.”

　　The project's controlling component—the undersea immersed tube tunnel—has a total length of 5,035 meters and is formed by joining 32 immersed tube sections plus a final closure joint. From the immersed tube prefabrication plant to the installation area, the tubes must be floated 50 kilometers, passing through seven channel transitions.

　　“The 50-kilometer ‘sea route’ is backed by an ecological calculation,” said Ning Jinjin, executive deputy chief engineer of the Shenzhen-Zhongshan Link project department of CCCC ** Harbor Engineering Co., Ltd. The immersed tube prefabrication plant for the Shenzhen-Zhongshan Link was upgraded and renovated from the Guishan Island immersed tube prefabrication plant used for the Hong Kong-Zhuhai-Macao Bridge. Compared with building a new prefabrication plant, “reusing the old” can effectively reduce the scale of offshore construction and lessen the impact on the white dolphin nature reserve.

　　Producing the immersed tubes is only the ** step; how to quickly float them into place became a new test. The project team creatively proposed a plan to build an integrated immersed tube transport and installation vessel. “The integrated vessel has self-propulsion capability. Compared with traditional towing schemes, it can reduce channel dredging by more than 10 million cubic meters and lower exhaust emissions by about 1 million cubic meters, effectively protecting the marine environment where the white dolphins live,” Ning Jinjin said.

　　Precise construction—

　　Innovative subsea construction techniques effectively protect the Lingdingyang ecology

　　The Shenzhen-Zhongshan Link undersea tunnel is about 6.8 kilometers long and is the world's longest and widest steel-shell concrete immersed tube tunnel. The placement of each immersed tube section is crucial.

　　As construction entered its critical period, difficulties followed. “The Shenzhen-Zhongshan Link construction area is located in the Pearl River Estuary, where vessels pass in a constant stream, causing significant disturbance to the seabed foundation bed,” said Guo Hongguang, captain of the “Sihang Guji” vessel of CCCC Fourth Harbor Engineering Co., Ltd. The silt on the seabed surface at the construction site has a water content exceeding 60 percent; stones thrown onto it sink as if into “mud soup.” To place the immersed tubes at predetermined positions deep in the sea, the seabed must be treated to reduce settlement.

　　How to place the immersed tubes on the seabed “silently” became a major challenge for the builders.

　　There are usually two ways to reinforce the seabed foundation: first, excavate the deep-sea silt and then carry out rock dumping; second, use deep cement mixing piles to reinforce the soft soil foundation.

　　“The ** scheme had lower costs, but to better protect the white dolphins' living environment, we ultimately decided to adopt the second scheme.” Recalling the process of deciding on the scheme, Wang Yaopeng, former director of the project's engineering technology department, said that deep cement mixing can form a high-strength improved foundation in a short period. More importantly, it can mix seabed silt with cement mortar to form long piles, thereby effectively protecting the Lingdingyang ecology.

　　Moreover, to better protect the white dolphins, the Shenzhen-Zhongshan Link construction team of the Second Company of CCCC Fourth Harbor Engineering Co., Ltd. also specially invented a national utility model patent—a whole-vessel anti-pollution system for deep cement mixing vessels. Through this system, two anti-pollution barriers can be formed, effectively preventing sewage generated by pile driving from entering the seawater and avoiding pollution of the white dolphins' habitat.

　　New difficulties continued to arise during construction. Soon, the builders discovered that in the immersed tube foundation trench area of the Shenzhen-Zhongshan Link, there was also a 2.6-kilometer-long granite zone, clinging tightly to the trench bottom like a “magnet.” Only after it was cleaned up could immersed tube installation proceed.

　　“Underwater blasting is the most direct method, but it has a greater impact on the ocean,” said the person in charge of the Shenzhen-Zhongshan Link project at CCCC Guangzhou Dredging Co., Ltd. Abandoning traditional seabed blasting, the team dispatched a “golden combination”—the heavy grab dredger “Jinxiong” and the “Jinjian,” equipped with rock-breaking rods—to excavate at a high precision of 0.6 meters 38 meters below sea level, carving out a sea route through a geological environment full of granite.

　　From the smooth placement of the first immersed tube section to the successful installation of the last, placing 32 immersed tube sections on the seabed took a full three years. In addition to technical support, the project specially compiled the “White Dolphin Protection Management Manual,” which not only clearly designated the captain of each construction vessel as the person directly responsible for white dolphin protection, but also assigned full-time and part-time dolphin observers to monitor white dolphin activity in real time, day and night, year after year, building a protective barrier for the white dolphins.

　　Green construction—

　　Scientifically handling domestic and construction waste and carefully protecting the marine environment

　　“Attention all vessels: crew members must not throw any garbage into the sea. Everyone must hold out to the end!” On June 7, at the site of temporary facility dismantling for the Shenzhen-Zhongshan Bridge, Liao Wenlong, the relevant person in charge of the Shenzhen-Zhongshan Link project at CCCC Second Harbor Engineering Co., Ltd., reminded the construction workers over the radio.

　　Looking into the distance from Ma'an Island in Zhongshan, Guangdong, the Shenzhen-Zhongshan Link winds over the deep blue sea, sometimes leaping into the air in the form of a bridge, sometimes diving into the sea as a tunnel. At the bridge-tunnel transition is the world's sea bridge with the highest navigational clearance—the Shenzhen-Zhongshan Bridge.

　　Super projects often require super-large teams. How should the domestic waste of the construction team and the production waste generated during construction be handled to minimize the impact on the marine environment? This places higher demands on green construction.

　　Plan ahead and optimize the layout to minimize the “footprint” of offshore construction.

　　“Sand and gravel transport vehicles must all ‘wear outer garments’ to prevent dust; mixer trucks entering and leaving the mixing station must ‘take a shower’ and then pass over a section of moisture-absorbing mats...” Liao Wenlong recalled. In addition, the tops of the powder storage silos were equipped with dust collectors.

　　Strengthen management and carry out regular transfer. “We strictly implement waste sorting management and regularly transfer waste for treatment,” Liao Wenlong said. After five years, the bridge completed all processes including pile foundations, bridge towers, and steel box girder construction. “We leave no garbage behind—only a bridge.”