China's bridge of size

It's 30 miles long, will cost £6.6bn to build, can handle earthquakes of magnitude 8.0, and withstand the impact of a 300,000-tonne vessel

Couples wander along Lovers' Promenade in Zhuhai, taking photographs against the backdrop of the gambling enclave of Macau, enjoying the view of the South China Sea. But within sight of the skyscrapers and casinos of Macau, a major transformation is taking place, and in six years' time when the couples look out, their holiday snaps will have a backdrop of the longest sea bridge in the world.

Building work has just started on the 30-mile Hong Kong-Zhuhai-Macau Bridge, which will link China's southern economic hub of Guangdong province to Hong Kong and Macau.

The scale is breathtaking. The bridge is one of the most technically complicated landmark projects in China's, and the world's, transport history. Not many bridges, for example, include a tunnel section that travels underwater. And it will bring economic ties closer in the region, underlining the Pearl River Delta's status as one of the world's great economic powerhouses.

Everyone is talking about it, from chief executives happy that it will boost the area around Zhuhai, which has been slightly neglected in favour of manufacturing zones like Shenzhen or Dongguan, to those living in the region who are keen to be able to see what is going on in the economic hotspots of Macau and Hong Kong.

But not everyone is as enthusiastic. Environmentalists are worried about the local dolphin population, while some Hong Kong residents fear that the bridge could mean travellers head straight past the former Crown colony without stopping.

Whatever the doubts, the size of the undertaking has given the bridge an unstoppable momentum of its own. When it is finished in 2016, the 73 billion yuan (£6.6bn) bridge will be a six-lane expressway that can handle earthquakes up to magnitude 8.0, strong typhoons and the impact of a 300,000-tonne vessel.

Traffic will travel at around 60mph, and it means that travelling between these economic powerhouses will only take half an hour, compared to three or four hours now. The vast manufacturing towns of the Pearl River Delta have been the engine of China's remarkable economic growth in the past three decades, and the whole region accounts for around 40 per cent of China's gross domestic product (GDP), so effective transport links are crucial.

The British-based engineering group Arup is doing design work for the project, and according to Naeem Hussain, Arup's global bridge leader, the difficulties are considerable. "The challenging part in terms of design was to trying to have the minimal environmental impact," said Mr Hussain, who is based in Hong Kong. "We have the white dolphin here and we wanted to make sure we don't impact the water flow. And also we wanted to ensure that the form of the construction doesn't pollute the water."

Environmentalists were angered when they heard of the decision to build a bridge across the natural habitat of the endangered white dolphin, known as "the panda of the ocean" because of its slim survival chances.

To try to preserve these imperilled creatures, the city of Zhuhai has set aside a preserve of 180 square miles to help the animal. There are about 2,000 white dolphins left in China, and more than half live in the Pearl River estuary. The builders have also tried to stop pollution in the area. "There is a submerged tunnel near Chep Lap Kok airport on Lantau island. You couldn't put a bridge with tall towers near the airport. The immersed tube is the longest in the world," said Mr Hussain.

Each of the bridge's piers will be 557ft high, and the design team has minimised the structure's impact on estuary flows by limiting the size and number of columns in the water. "Taking off from Hong Kong airport you will get a fantastic view. The bridge curves over 12.5 miles between Hong Kong and Zhuhai and Macau. We wanted each of the bridges to have their own elegant look but with a unifying visual look," he said.

The first stage of the project is a land reclamation, which will create a large artificial island off Zhuhai, one of two islands being made in the ocean for the project. This island will become the customs point for people crossing to Macau using the bridge.

Currently, most people crossing from Hong Kong to Macau use the ferry services, but they do not carry vehicles and are vulnerable during the typhoon season in the summer months, so the bridge is seen as a major impetus to commercial traffic between the two cities. It will also mean traffic is 24/7, whereas currently the border is closed at night.

The Hong Kong chief executive, Donald Tsang, is an enthusiastic backer of the plan because it will increase throughput there. But local opposition voices fear the effect will be to reduce passing trade. In some ways, the debate is similar to the angry voices when British road builders built bypass roads that meant some cities have lost a lot of relevance.

For the Chinese government, represented at the opening ceremony by a rising star of the Communist Party tipped to be the next premier, Li Keqiang, these fears mean nothing. People will just move, right?

The cost of the project will be shared among the central government in Beijing, Hong Kong and Guangdong provinces. It is a key element in a plan released by China's top economic planning authority, the National Development and Reform Commission, which aims to integrate Hong Kong and Macau into the Pearl River Delta area by 2020.

That development will be as visible on Hengqin Island as anywhere. Currently farmland and home to about 3,000 people, the development plan will see it transformed into a major business zone, at a cost of billions of yuan. The island's population is expected to increase to 280,000 by 2020. Still, if Lovers' Promenade may not be quite so intimate in a few years' time, it will certainly offer a spectacular view.