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09 Oct 2013
Mark Twain once said, “Buy land, they’re not making it anymore.” Twain’s old saw about investing in real estate since there’s only so much of it to go round still holds true for most of the world. However China, as in so many other areas, has been determined to buck this trend.
Stretching back over the past five decades, China’s coastline has been expanding inexorably, thanks to the process of reclaiming land from the sea. Reclamation has allowed developing conurbations and cities to grow beyond their original scope to accommodate their changing economic and infrastructure needs. And although China’s growth continues, the cost and environmental impact of the practice is driving a new approach.
The rationale behind the use of reclamation is simple, according to Tommy Ng, director for design, engineering services at Atkins in China – with ongoing urbanisation, cities need space to accommodate the people that move there.
“City managers also realise that coastal areas are in short supply and thus tend to have high land values. By using reclaimed land in front of the existing coastline, they can gain additional value,” he says.
In the past, regional governments across China have used reclamation as a shortcut towards urban growth. The country’s 18,000km of coastline have been the site of reclamation projects for the past 40 years. Over the past 50, China lost more than half of its coastal wetlands. And in 2009 alone, over 150km2 were reclaimed. Projects on the scale of Caofeidian, near Tangshan, which transformed isolated sandbars into a major industrial park and deep-water port, have become commonplace along the Chinese coast.
But uncontrolled reclamation brings risks. “With reclamation, the easiest method is to pull all the things around it into the sea to create the piece of land without any control,” says Ng. “Of course, that will create pollution in the sea and damage the ecology. New land may also contain materials like heavy metals and other pollutants.”
Drainage channels can be affected, local wildlife populations displaced, delicate tidal ecosystems disrupted and seabed integrity damaged.
It is factors like these that have given Atkins’ planners and engineers pause for thought.
“The question we need to ask is whether we need to reclaim the land – are there other, better alternatives?” says Ng. “If it is required, then we should focus on whether it will have an impact on the environment and the ecology, or whether the new piece of land reclaimed will be sustainable.”
Ng and his Atkins colleagues have been working to understand the impact of reclamation and, having done that, to design solutions, some involving reclaimed land and others using completely alternative methods of land use.
Currently, every project that features an element of reclamation must go through the following assessment:
If reclamation is called for, then the key strategy for Atkins is to get involved early in the planning process, using hydrologists, environmental scientists and engineers to fully understand the tidal patterns and wind direction, as well as any sensitive areas, such as coral or species of fish, water depth and so on.
“You need to fully understand all the parameters of a project, including these sensitive issues, both before you begin the work and as it progresses. This helps to ensure that the plan is on the right track from the start and that the need for any mitigation measures can be minimised,” says Mark Harrison, director for urban planning consultancy at Atkins China.
When it comes to urban design projects featuring an element of reclamation, greater scrutiny is leading to more innovative thinking. As Wing Wong, Atkins’ associate director for environment, explains that means considering a broader range of options.
“Ultimately, you’re looking to reduce the impact in some areas and to enhance the environment in others,” she says. “For example, if you were doing reclamation in an area that has marginal marine ecology but where there may be a loss to the marine environment, enhancing other areas that have greater potential can be more beneficial to the environment overall. For each project, the objective must be to reduce impacts to a level that can be accepted.”
This has been the case in Hong Kong recently and the proposed construction of the Integrated Waste Management Facility at Shek Kwu Chau is one example. Here, cellular cofferdam and circular cell breakwater have been suggested in the construction design to minimise dredging and filling activities, and the associated environmental impact.
“The compensation measures for habitat loss for this project are substantial,” says Wong. “They include the translocation of corals in the area; measures to minimise the disturbance to finless porpoise, including reducing habitat loss and avoiding types of construction during peak seasons; and allocating marine habitat for conservation purposes through the designation of a new 700ha marine park. The latter will be enhanced through the deployment of artificial reefs, the release of fish fry and a comprehensive management programme.”
Another ambitious example is the work undertaken on the Hong Kong Zuhai Macau Bridge – Hong Kong Link Road (HKZMB HKLR) / Hong Kong Boundary Crossing facility. These were the first projects of their kind to implement a non-dredge reclamation solution. For the 150ha artificial island, this was achieved by forming the seawalls by sinking large diameter circular steel cells through soft marine mud and filling them with inert material – geotextile and a two-metre-thick sand blanket. Vertical drains are then installed to accelerate consolidation of marine mud.
The benefits of this approach, Wong explains, will be a reduction in the amount of dredging and dumping of marine mud by about 22mm3 and reducing the amount of backfill material needed to be imported.
“This means we reduce the impact on water quality in the area and on the marine ecology, especially the Chinese white dolphins’ habitat. The project also includes an extensive monitoring programme of the Chinese white dolphins, coral translocation and intertidal surveys.”
This determination to radically reduce the environmental impact of new developments underpins much of Atkins’ work. As Ng explains, it often involves pioneering new geotechnical strategies, such as the temporary reclamation techniques used in the Central Wan Chai Bypass – Causeway Bay Shelter Section project.
“This project involves the construction of a 710m-long section of vehicle tunnel, which is a strategic (dual three-lane) trunk road along the north shore of Hong Kong Island,” Ng explains. This road section comprises tunnel box structures running beneath the existing seabed within the Causeway Bay Typhoon Shelter. When it’s completed, the bypass will provide an expressway for the east-west traffic between Central and North Point.
Except for the portion of tunnels immediately beneath the Cross Harbour Tunnel entrance, Ng and his team have come up with a plan that will see the proposed tunnel works constructed by a cut-and-cover method using diaphragm walls. These require the construction of a working platform above water level by means of temporary reclamation, typically 80-to-90m wide, supported by blockwork seawalls placed on the dredged seabed.
“To support the excavation of up to 30m in depth, high capacity steel props are installed in stages as excavation progresses,” Ng says. “When the tunnel structures are completed, the temporary reclamation will be removed and the seabed reinstated.”
Clear evidence, then, that reclamation can be done without ruining the surrounding environment. However, given that much of the reclamation efforts have been focused on developing land for infrastructure (water treatment or sewage plants, for instance) then it follows that finding alternative ways of housing these facilities becomes a top priority.
“A current government study is looking at either rock cavern or reclamation outside Victoria Harbour in Hong Kong,” explains Wong. “That involves trying to relocate some of the ageing infrastructure, which can take up large amounts of land. It might mean putting those underground and freeing up land area for further urban development.”
Atkins engineers have been working with municipalities to develop the use of cavern and tunnel technology to house a range of facilities that traditionally take up swathes of city land. Hong Kong University was one of the first such projects when, to extend its campus, authorities decided to dig out caverns in order to house two saltwater reservoirs. The scheme won awards and has proved that such solutions can work.
So what does the future hold? Is reclamation dead or will the practice continue albeit in a more controlled and sustainable way? The answer to that lies in the work being done both above and below ground in cities across Asia, where a more integrated approach to urban design is leading civic authorities and planners to accept that better land use, and not more land use, is the key to designing a sustainable future for China’s cities.
With its long history – and better oversight – reclamation promises to provide innovative approaches to the vexed issue of sustainable development while making the most of that very precious commodity, real estate.
The challenge is for engineers to continue their search for ways to support this goal, managing the impact of reclamation while working on alternative, ever more sustainable approaches.
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