Transport and logistics

Central-Wan Chai Bypass inspires call for air purification systems across other high-traffic zones in Hong Kong

  • Long-awaited HK$36 billion link set to open, boasting world’s largest air treatment work of its kind at cost of HK$250 million
  • Faster journey time also expected to cut carbon dioxide emissions by 11,000 tonnes annually, ‘equal to the absorption capability of 67 Victoria Parks’
PUBLISHED : Friday, 04 January, 2019, 10:02am
UPDATED : Friday, 04 January, 2019, 11:12pm

Green groups have urged the Hong Kong government to set up more air purification systems in high-traffic areas, inspired by the world’s largest version for the Central-Wan Chai Bypass, which can remove at least 80 per cent of key pollutants from roadside emissions.

The government announced earlier that the long-awaited HK$36 billion (US$4.6 billion) bypass would open to traffic on January 20 after nearly 10 years of construction plagued by delays and cost overruns.

The 4.5km link, comprising a flyover in Central and a 3.7km tunnel, is expected to ease chronic congestion between North Point and Central, especially on Gloucester Road, Harcourt Road and Connaught Road Central.

Central-Wan Chai Bypass to open on January 20 after decade of delays

The bypass is expected to cut travelling time between Central and the Island Eastern Corridor from about half an hour to five minutes, and divert traffic from other parts of the city. Authorities said a faster journey could also mean less carbon dioxide emissions from vehicles.

But the greenest feature is an air purification system in the tunnel – the first in Hong Kong and the largest of its kind in the world in terms of air volume handled – which can remove at least 80 per cent of harmful suspended particulates and nitrogen dioxide, two key roadside pollutants.

“Every hour it can handle 5.4 million cubic metres of vehicle exhaust,” Highways Department project manager Kelvin Lo said.

Large fans will suck tunnel exhaust into air purification plants in three ventilation buildings along the tunnel. The air will first go through an electrostatic precipitator which charges and separates harmful particulates. It then passes through a denitrification filter which uses activated carbon to remove nitrogen dioxide. Purified air is then discharged from the system.

Lo added that the faster journey time could also reduce carbon dioxide emissions by 11,000 tonnes annually.

“This is equivalent to the absorption power of 480,000 trees, about 67 Victoria Parks,” he said.

This is equivalent to the absorption power of 480,000 trees, about 67 Victoria Parks
Kelvin Lo, Highways Department

World Green Organisation chief executive Dr William Yu Yuen-ping called on the government to explore the feasibility of installing the system at other high-traffic tunnels and areas to improve air quality.

“We welcome this clean air initiative. We hope the government tells us more about this system, such as how it will be maintained and whether the filter cores will be replaced regularly, as well as how filtered pollutants are treated,” Yu said.

The department also saw the project as an opportunity for more greenery in the urban environment.

The West Ventilation Building of the tunnel section has a streamlined green roof which stretches over the Central Tunnel Portal and is shaped like a suspended leaf, while scrubs and lianas have been planted around the East Ventilation Building. The East Vent Shaft was also designed to look like the sail of a boat.

The air purification system cost HK$250 million, 5 per cent of which will pay for the annual maintenance cost, according to government officials who took lawmakers on a tour of the bypass on Friday.

Civic Party legislator Jeremy Tam Man-ho urged the government to closely monitor the data, saying his only concern about the system was that one vent shaft for the discharge of filtered air was located just 200 metres from North Point’s residential district.

“Although the government said purified air would be discharged through the vent shaft, it is so close to the residential district in North Point that I wonder if it will affect the residents there,” he said.

Tam also raised concerns about whether the bypass would create a bottleneck effect along the stretch of Wan Chai enclosed by construction work.