Hong Kong announced on Tuesday a HK$624 billion (US$79.5 billion) price tag for its Lantau Tomorrow reclamation plan to produce 1,700 hectares of new land in what would make it the most expensive infrastructure project in Hong Kong history.

The city’s officials said the money would include the cost of building artificial islands around Lantau, Hong Kong’s largest island, as well as paying for further reclamation projects in nearby waters. Its goal would be to provide space for 260,000 new apartments, with 70 percent of them set aside for public housing.

Officials also dismissed fears that the size of the project would deplete the government’s coffers as revenue from land sales should cover the costs. An estimate by the city’s Institute of Surveyors suggested that land sale revenue generated from the project’s initial phases alone could reach over HK$1.1 trillion. However they also noted that all estimates were ballpark figures.

Neither are officials worried about the financing of the scheme as the money would be spent over a period of 10 to 15 years, meaning funding requirements of only around HK$40 billion each year.

The city’s Development Bureau also added that once the reclaimed area is transformed into Hong Kong’s third central business district (in addition to Central and Kowloon East), it would generate around HK$141 billion in economic benefits each year.

Still, the total cost of HK$624 billion constitutes more than half of the city’s total financial reserves of HK$1.1 trillion, and was even higher than the HK$500 billion a government estimated last month. Also, budget over-runs are a main concern in public projects. A recent example was the cost of the Guangzhou-Shenzhen-Hong Kong Express Rail Link, which exceeded by about 30% the initial amount applied for from the Legislative Council.

Pro-Beijing lawmakers have sided with the government to back the proposed project, arguing that it would pay for itself despite the hefty price outlay.

The figures were estimated on September 2018 prices, but the reclamation will not begin until 2025. The first group of residents could move in some time after 2032.

There will be six rail and road corridors and links to connect the artificial islands with Hong Kong Island, Lantau Island, Sunny Bay and New Territories West.

The government also brushed aside environmentalists’ concerns that climate change could lead to flooding on the artificial islands, saying the new islands would be around six to seven meters above sea level.

But a former head of the Hong Kong Observatory has added his voice to criticism of the project, stressing that a feasibility study of the plan needed to consider risks like climate change over the next two centuries, such as stronger downpours, storm surges, rising sea levels and more frequent super typhoons. Lam Chiu-ying warned that the new islands to be created are particularly susceptible to floods and storms in a city that is usually battered by several typhoons each year.

He told reporters that there is a need for proper breakwater and flood discharge facilities to be in place for the islands to avoid disasters. He also said that the government should consult its own meteorologists at the observatory when it studies the potential effects of climate change.