A report from government engineers has found only one viable option for the controversial Central-Wan Chai bypass - reclamation.
The bypass is aimed at easing traffic congestion and providing a traffic link to proposed development on harbour reclamation.
The government wants to build its new offices on the Tamar site in Admiralty, as well as a large commercial district.
Critics have stepped up lobbying against the plans, with one group releasing a proposal calling for the entire area to be converted into a harbourfront park.
The report, which will be presented behind closed doors to a subgroup of the Harbourfront Enhancement Committee today, says engineering consultants believe a deep-water tunnel for the site would require too much additional harbour reclamation at an entrance in North Point.
An inland tunnel is dismissed as unfeasible because of existing tunnels, buildings and utility cables.