On-site preservation of Queen's Pier has been called 'infeasible' because of the difficulty in changing the location of a planned MTR tunnel, according to the Institution of Engineers.
The group believes the most practical way to preserve the pier would be to dismantle it and rebuild it later - either elsewhere or on the original site after tunnel construction.
'We consider it technically infeasible to change the alignment of the planned airport railway extended-overrun tunnel,' institution spokesman Wong Chi-ming said.
'Shifting it to avoid the pier would involve gazetting and statutory procedures that would incur huge prolongation costs under the Central Reclamation III contract,' Mr Wong said.
Underpinning the pier for building the tunnel would involve big technical difficulties and safety hazards, he added.
'This is an extremely risky option,' he said. 'The substantial width of the tunnel - more than 40 metres - also makes it highly infeasible.'
The group estimated such an option would take 31/2 years to carry out and incur extra costs of HK$865 million - HK$565 million in additional work and HK$300 million in delay costs.
Another popular proposal - rolling the structure away and then back after tunnel construction - would be risky and expensive, Mr Wong said.
'Uneven movements, which are hard to anticipate or control, can cause damage to the structure during the rolling process,' he said.
Extra costs involved in that option were estimated to be HK$430 million and it would also take 31/2 years to carry out, according to the group.
The institution concluded that 'it is more sensible to dismantle the pier structure piece by piece and reassemble them afterwards', which would only cost about HK$80 million and take four months, Mr Wong said.
The group stressed that it was making a 'purely technical' assessment on the popular options.
'We believe the government has the responsibility to preserve heritage that is treasured by residents,' institution member Victor Cheung Chi-kong said.
'But it must also avoid wasting public money.'
The institution's view echoed an earlier suggestion by Secretary for Housing, Planning and Lands Michael Suen Ming-yeung, who said the only feasible option to keep the pier was dismantling and rebuilding it.