The Airport Authority appears to be softening on its reluctance to conduct an extra study on the social costs and benefits of building a third runway, and to gauge carbon emissions from aircraft.
The authority has also pledged to identify the practical methodologies for such a study to ease public concerns over the development.
However, the operator of Hong Kong International Airport insisted it could not set a deadline to decide if it would conduct the study, as it needs to ascertain what the study would involve and how it could be done.
If it decides that such a study is feasible, it would be conducted with the current environmental impact assessment for the HK$130 billion development of 650 hectares of reclaimed land north of the airport.
The authority was willing to 'go to the extra mile to assess other potential impacts where possible', Kevin Poole, its deputy director of projects, said yesterday in response to calls from environmental protection groups and lawmakers for a 'social return on investment (SROI)' study on the project.
But Poole said the authority could not commit to an extra study as yet. 'It is difficult to commit to something before we understand what we are committing to,' he said.
The authority had earlier ignored calls for the study - covering areas such as health and social impact - which environmental protection groups argued was necessary to gauge the real costs and benefits of the runway project.
An SROI study has been described as a 'principles-based method for measuring environmental and social value not currently reflected in conventional financial accounts'.
Some groups had pledged to boycott the authority's advisory groups if the study was not conducted.
They include Dr Samuel Hung Ka-yiu, chairman of the Hong Kong Dolphin Conservation Society.
However, Poole said the authority's preliminary research showed that the SROI methodology was applied only once - for the expansion plan of Heathrow airport that was done by the New Economics Foundation, a British think tank.
Dr William Yu Yuen-ping, head of WWF Hong Kong's climate programme, an advocate for the study, believes the authority has softened its stance.
'It is never our intention to block the project by requesting the study,' Yu said.
'We only want the project to comply with best international practices.'
Yu said he was prepared to help the authority work out a feasible methodology by inviting World Bank experts or academics to provide their expert advice.