The new bypass will be a three-lane trunk road with a 3.7-km-long tunnel, connecting the Rumsey Street Flyover (Central) and Island Eastern Corridor (North Point). Work began in 2009 and completed recently. When opened, estimated travelling time from Central to North Point will be approximately five minutes, significantly reduced from the original half-an-hour.

WSP is responsible for all MEP design for the Bypass’ buildings and tunnels. Systems include a tunnel ventilation system, air purification system, tunnel lighting system, central control and monitoring system, traffic control and surveillance system, mechanical ventilation and air-conditioning system, fire services system, plumbing & drainage system, electrical system and vertical transportation system.

The tunnel is equipped with an Air Purification System – the first in Hong Kong and one of the largest of its kind in the world – which can handle 5.4 million cubic metres of tunnel exhaust per hour and reduce 80% of the respirable suspended particulates and nitrogen dioxide from the tunnel exhaust.

WSP contributed to the design of the Air Purification System. The advanced purification system not only captures dust via an electrostatic filter, but it also captures nitrogen dioxide using a De-NO2 filter to improve visibility and air quality.

The tunnel exhaust will pass through two major components in air purification plants installed in three ventilation buildings along the tunnel section of the project. When the air enters the air purification system, it first goes through the electrostatic precipitator which charges and separates respirable suspended particulates from the tunnel exhaust. Charged particulates are attracted to collector plates at this stage. The air then passes through the denitrification filter which uses activated carbon to remove nitrogen dioxide. Purified air is then discharged from the system to improve the nearby air quality.

In case of fire, the Air Purification System is bypassed and the tunnel ventilation system will control and effectively discharge smoke to ensure the safety of tunnel users. The purification system provides added benefit to the surrounding environment as well; the Air Purification System produces cleaner outdoor air for local residents around the tunnel portals and ventilation buildings.

The Central - Wan Chai Bypass is also the first tunnel project in Hong Kong to employ Building Information Modeling (BIM). By using BIM to virtually imitate the construction sequence, the project team can successfully identify uncertainties, potential impacts and safety concerns before construction even begins. As a result, the project schedule is potentially shortened, and resources and budget are more accurately defined.