Delegations from three Asean dialogue partner countries - China, Japan and South Korea - yesterday visited three stations on the upcoming Downtown Line 3 (DTL3), which is scheduled to open on Oct 21.

The visit was part of the Asean Transport Ministers Meeting that also began yesterday.

The three stations - Bencoolen, Kaki Bukit and Upper Changi - were built by firms from the three countries, namely China State Construction Engineering Corporation, Sato Kogyo and Samsung C&T Corporation.

Firms from these countries have also expressed interest in the Kuala Lumpur-Singapore High Speed Rail project, expected to be completed in 2026.

A tender for the project's assets company - responsible for designing, building, financing and maintaining all rolling stock and rail assets for the project - is expected to be called by the end of this year.

Mr Masayoshi Isono, the international affairs special representative for Japan's Ministry of Land, Infrastructure, Transport and Tourism, led an eight-member Japanese delegation on a visit to Bencoolen station. The delegation included Japanese Ambassador to Singapore Kenji Shinoda.

Sato Kogyo civil engineering general manager Hirotaka Onawa showed them around the station, which was completed earlier this year.

Mr Onawa noted some of the challenges the firm faced when building Bencoolen station which, at 43m below ground level, is the deepest MRT station in Singapore.

The station had to be constructed at such a depth because of the number of buildings above it, as well as the existing North-South and Circle line tunnels, which run above the Downtown Line.

Tokyo's Roppongi station on the Toei Oedo line is the Tokyo Metro's deepest station at 42.3m below the surface, he said.

Bencoolen station's construction work was also carried out in close proximity to existing buildings, and Mr Onawa said excavation also had to be done in the hard Fort Canning boulder bed.

"We had to deploy a lot of machines within a very narrow space and, at the same time, keep up our productivity so as to complete the project on time," he said.

Separately, the Chinese delegation - led by China's Vice-Minister of Transport Dai Dongchang - visited Kaki Bukit station, while the South Korean delegation - led by Mr Cho Seongkyun, international cooperation and trade division director for South Korea's Land, Infrastructure and Transport Ministry - visited Upper Changi station.