Hong Kong International Airport (HKIA) has completed the construction of its third runway, employing innovative engineering and environmental strategies designed to balance infrastructure expansion with marine conservation. The development, comprising 650 hectares of reclaimed land adjacent to the existing airport, faced significant challenges due to the presence of decades-old, contaminated mud pits beneath much of the project area.
Traditional reclamation methods, which typically involve dredging, posed a risk of disturbing these sediment deposits and releasing pollutants into the surrounding waters. To mitigate this, the Airport Authority Hong Kong adopted deep cement mixing (DCM), an approach not previously used on such a large scale. This method involves injecting cement slurry into the soft seabed mud, reinforcing the ground with over 360,000 solidified columns. The process stabilized the reclaimed land while containing contaminants undisturbed beneath the surface.
Tommy Leung King-yin, executive director of engineering and technical services for the Airport Authority, highlighted the environmental and operational benefits of this technique. Although DCM was more costly upfront, it reduced the project’s settlement time by approximately one year and lowered the demand for fill material by about 10 percent, while preventing pollution during construction.
Beyond ground stabilization, the project incorporated other low-impact construction techniques. Notably, horizontal directional drilling was used to reroute two 5.2-kilometer aviation fuel pipelines beneath the seabed, avoiding dredging a trench and thus minimizing ecological disruption. This installation is the longest pipeline executed worldwide using this method.
The airport’s expansion project introduced more than 250 environmental measures to control potential impacts from both construction and subsequent operation. Among these, the 13-kilometer sea wall surrounding the reclaimed area features over 500 eco-enhanced blocks designed to support marine life. These blocks possess grooved surfaces and water-retaining cavities that emulate natural rock pools, providing habitats during low tide and shaded shelter for various species.
Professor Kenneth Leung Mei-yee, director of the State Key Laboratory of Marine Environmental Health at City University of Hong Kong, noted that such engineered sea walls could double the biodiversity found compared with conventional designs. In support of broader marine conservation efforts, the Airport Authority has also installed 600 artificial reefs and introduced nearly 90,000 fish fry to the surrounding waters.
Additionally, the project has aided in the establishment of the North Lantau Marine Park, the largest marine protected area in Hong Kong at 2,400 hectares. This park is part of an expanding network of conservation zones aimed at preserving marine ecosystems in the region.
Professor Leung described these initiatives as a significant advancement in promoting ocean sustainability, reflecting a growing recognition of the importance of integrating environmental stewardship with large-scale infrastructure projects.