Blog Articles from former Secretary for Development, Mr Paul Chan - (1/12/2013 - 15/01/2017)

The construction of the Central–Wan Chai Bypass (CWB), which serves to ease traffic congestion in the north of Hong Kong Island, is now in full swing.  As the project requires reclamation on an appropriate scale along the Wan Chai waterfront, many public facilities have to be relocated.  For example, we installed a mega-size precast drainage culvert unit at the Wan Chai waterfront as an extension to the existing drainage outfall at the end of August.  With the completion of the CWB, the new land formed at the waterfront will provide a brand new promenade for public enjoyment.

In recent years, we have been adopting more precast construction in public works projects.  The principle is similar to building blocks – delivering precast units from casting yards to work sites for assembling.  This not only helps enhance cost-effectiveness but also improves construction efficiency, thereby enabling early use of the completed infrastructure by the public.  In addition, the effective use of precast units will also help resolve complex engineering challenges and overcome site constraints.

However, it is never easy to use precast units in real situations.  First of all, the fabrication of mega-size precast units requires a large casting yard.  Owing to the limited space in Hong Kong, precast units are mostly fabricated in casting yards in the Mainland at present.  Such mega-size precast units can weigh up to thousands of tonnes.  Taking the above-mentioned precast drainage culvert unit as an example, the area of the largest unit is as large as that of a basketball court, weighing 1 100 tonnes (approximately equivalent to the weight of 60 double-decker buses).  To deliver it from the casting yard to Hong Kong is by no means an easy task.  During assembling, if the site condition is complicated, such as working over the sea, precise engineering calculations coupled with seamless manpower input are needed to accomplish the work accurately.

About three years ago, we carried out a major precast unit installation during the construction of the CWB.  At that time, we had to carry out reclamation off the shore of the original Fenwick Pier in Wan Chai (i.e. to west of the Hong Kong Convention and Exhibition Centre) for the construction of one of the tunnel sections of the CWB.  However, the existing cross-harbour tunnel of the Mass Transit Railway (MTR) Tsuen Wan Line runs underneath the seabed in the reclamation area. As a result, any construction works (including the reclamation) should not impose additional loading onto the MTR tunnel or cause any ground movement, to avoid any unpredictable consequences.  To overcome this engineering challenge, the engineering team came up with the idea of constructing two rows of bored pile walls (involving a total of 56 piles) along the two sides of the MTR tunnel, followed by installing on the bored pile walls a mega-size precast unit of roughly the size of a football pitch and about four-storey high, so as to properly cover and protect the existing MTR tunnel, thereby enabling the related works of the CWB to be carried out.

As the precast unit was enormous in size, with a volume of roughly the same as five standard swimming pools and a weight of nearly 45 000 tonnes (equivalent to the weight of about 100 Airbus A380 passenger carriers), each stage of works, from fabrication, delivering to assembling, was highly complicated.  To put it simply, the engineering team first fabricated the precast unit at a seaside old quarry in Zhuhai.  When the unit was fabricated, the rock at the seaside of the casting yard was removed so that seawater was drawn in to float up the unit.  The unit was then towed by six barges from Zhuhai to the Victoria Harbour in Hong Kong for 72 kilometres, a voyage which took an entire day.  Lastly, with the help of the real-time positioning system and survey equipment, the engineering team accurately installed this mega football pitch-sized precast unit onto the pre-built bored pile walls, thus successfully overcoming a major obstacle to the CWB project.  Words alone cannot describe this spectacular process.  Please watch the related video if you are interested in it.

In fact, in every public works project, colleagues of the works departments, contractors, engineering professionals and front-line construction workers work together whole-heartedly to resolve all problems with a common goal of providing more robust infrastructure for the betterment of Hong Kong.

Hong Kong boasts world-class engineering talent, techniques and experience, which enable us to overcome most of the engineering challenges. The main issues being faced by the public works projects at present are not engineering-related problems, but political challenges such as the frequent filibustering in the Legislative Council (LegCo) in recent years.  As the Administration, we will continue to address various public concerns as far as practicable and in a transparent manner.  We also hope that the public will objectively look at the efforts made by colleagues and front-line engineering staff in every project.  Superficial political slogans do not help resolve complicated problems in the real world.   Election for the next LegCo term is being held today,  I appeal to every voter to cast your vote for your favourite candidates to express your wishes about building Hong Kong and moving forward together.