The project cost 142 billion yuan (HK$178.8 billion) and is operated by the China National Petroleum Corporation. From this summer, it will provide a new source of gas to Hong Kong, replacing the supply the city has been drawing from Yacheng near Hainan Island since 1996 and which is now nearly exhausted. Work on the gigantic project began in 2008. A little over three years later, the main trunk went into operation across the mainland and in August last year the Guangzhou to Shenzhen stretch went live. Now, after a huge engineering effort, Hong Kong is about to join the network.

For us at CLP, bringing the natural gas on the final leg of its journey from Central Asia to Hong Kong was a significant challenge that involved building a 20-kilometre undersea stretch, testing our resources and ingenuity and requiring close co-operation to deal with a range of regulatory requirements. The operation involved hundreds of engineers working from the Zhong You Hai 101 Lay Barge, one of Asia's most advanced water-pipe laying and lifting barges that works in shallow and deep waters, carrying 200 pipefitters and welders.

The Hong Kong branch line of pipeline links Dachan Island, off Shenzhen, with Black Point power station. It took 1,600 carbon steel pipes, each 12 metres long and weighing approximately 13 tonnes.

Every section of the pipeline was meticulously checked. Each weld joint had to pass an automatic ultrasonic testing. The entire pipeline, including its coating and corrosion protection system, was thoroughly inspected before being laid into the seabed.

Laying the pipeline meant crossing three major navigation channels - the Tonggu channel and the Dachan Fairway in Shenzhen, and the Urmston Road in Hong Kong - used by a total of more than 400 vessels a day, including ocean-going vessels. Getting a permit to put our pipeline beneath the Urmston Road - one of the world's most heavily used marine channels - took three months of planning and discussions with Hong Kong and Shenzhen officials. Actually laying the pipeline took just three days.

A three-metre thick shielding was placed over the pipeline through the entire sub-sea route, to protect against any anchors being dropped or dragged from vessels. This included the marine channels, and a number of existing and planned anchor zones. In one stretch of the Tonggu channel in mainland waters, the pipes had to be dug in 27 metres below sea level for future marine planning of the channel, and to keep them safe from anchor damage.

Another complication was the proximity of the existing 780-kilometre Yacheng undersea pipeline. In Hong Kong waters, the new pipeline was in stretches laid 100 metres or less from the Yacheng pipeline.

The anchors of our lay barge had to be dropped 200 metres from the existing pipeline and a safety zone set out by buoys was set up as we worked to make sure the Yacheng pipeline was not affected.

Throughout the process, section by section and kilometre by kilometre, we worked closely with our colleagues at PetroChina - communicating in English, Cantonese and Putonghua - to ensure that we brought the very best expertise to each situation and difficulty as it arose. Through our joint efforts and team work, the construction process was completed safely, on schedule and without a single lost-time incident. For all of the engineers involved, the challenges - regulatory, logistical and linguistic - were huge. But we rose to those challenges and the rewards should be immense as Hong Kong taps into new, greener energy supply that we hope will serve it for generations to come.