Authorities said that the cost of building the section that would run past Hanoi’s Hoan Kiem (Sword) Lake as part of the capital city’s second urban metro project will increase by more than VND16 trillion ($690 million) to VND35.67 trillion ($1.5 billion).

A report submitted to the National Assembly by the Ministry of Planning and Investment says the cost increase is warranted by changes in the project scale, the currency's conversion rate, material price hikes, and higher management costs.

The cost adjustment would mean that each kilometer of the 11.5 meter section cost $143 million. The funds will be raised from the national budget and loans from the Japanese government.

The ministry said the increased investment cost was acceptable, comparing it with metro lines in Indonesia and Malaysia that were completed in 2014 and 2011 at the cost of $165.6 million and $125 million for every kilometer, respectively.

The section will be underground for nine kilometers as it runs from the Ciputra complex in Tay Ho and Bac Tu Liem districts to an intersection between Pho Hue and Nguyen Du streets in Hai Ba Trung District.

The adjustment will also increase the maximum speed of the metro from 90 km per hour to 120 kph and cut the number of coaches from 56 to 40.

The commercial operation deadline for this section, which will feature three elevated stations and seven underground stations, however, has been pushed back to 2027, which means 12 years after the original schedule.

Last month, the Ministry of Culture, Sports and Tourism cautioned that one of the section’s stations planned near the Sword Lake could violate the nation’s Cultural Heritage Law.

C9, the station, should be constructed out of the protected area of the lake relics, the ministry said.

It maintains that the station's location in the current plan, which is just 36 meters away from the Thap But (Pen Tower) and a meter deep from the ground level, would make construction difficult.

Digging the ground, putting up fences and felling all the existing trees will affect the ecosystem and scenery around the lake, it said.

Hanoi plans to build eight urban railway lines with a combined distance of 305 km, including three monorail segments, as per its development plan for 2030 with vision towards 2050.