The adjustment was included in a new appraisal report issued by the city’s Department of Finance for the first phase of the drainage system outside the airport area.
Approved in September 2025, the project is designed to channel water from Long Thanh airport into the Bung Mon and Da Vang streams, helping prevent flooding around the airport and nearby urban areas.
The drainage system will also support water discharge from several regulating lakes already built inside the airport complex.
The rapid urbanisation in Long Thanh Ward has increased concreted surfaces, reducing natural water absorption capacity and placing pressure on the existing drainage network.
The project includes about 19 kilometres of drainage infrastructure.
According to the Department of Finance, the investment increase was mainly due to an additional 22 hectares of land required for the project, while compensation and resettlement costs rose by about VND 524 billion.
Funding will include VND 1.2 trillion from the central government budget, with the remainder financed by Dong Nai City.
Long Thanh International Airport, one of Vietnam’s largest infrastructure projects, is expected to begin commercial operations by the end of 2026.