Building a third runway at Hong Kong International Airport is a daunting task. With a construction cost of HK$136 billion, not only is it the most expensive infrastructure project to build, the 650 hectares of sea reclamation - and its impact on the environment - is also set to be the biggest ever. It is, therefore, imperative for the Airport Authority to put up a convincing case for expansion, while ensuring the damage to the environment will be reduced to an acceptable level. Recently, the runway project has had its wings clipped by a government watchdog. In a rare move, the Environmental Protection Department has demanded more details on air pollution, marine life and aircraft noise before giving the green light. The information submitted will be open for public comment for two weeks. It is disappointing that the authority has apparently failed to do its homework and suffered a major setback. It shows that better efforts are needed to fulfil the environmental protection requirements under the law. The airport is the lifeline of Hong Kong. In an increasingly competitive world, the importance of maintaining the city's status as a regional aviation hub is beyond question. With the growth in passenger and cargo traffic expected to reach full capacity in eight years, a third runway is the right solution. On the other hand, a growing environmental awareness is holding back the pace of further development. The question is how to move forward while keeping the impact on air quality, marine life and local residents to the minimum. As public expectations for clean air and green living continue to grow, there is a need for the government to play a more pro-active role in vetting the environmental impact of infrastructure projects. The judicial review over the green assessment of the bridge linking Hong Kong with the Pearl River Delta is a good reminder that major building works may end up in court if they are found to be not properly scrutinised according to the law. Assessment should be professional rather than perfunctory. The authority is expected to redouble efforts to satisfy the assessment requirement and minimise the impact. It should be able to demonstrate that it is sincere in addressing critics' concerns and is taking steps to reduce any adverse impact. The idea was first formally put on the public agenda as early as 2006, just eight years after Chek Lap Kok came into operation. Since then, the exponential growth in air traffic has reinforced the case to further expand. As regional competition intensifies, Hong Kong cannot afford to stand still. It is time for the project to take off. What we need are more effective efforts to address concerns over our environment.