Singapore deep tunnel phase II: consultants eagerly await tender decision

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Singapore deep tunnel phase II: consultants eagerly await tender decision

Major engineering consultancies are eagerly anticipating a tender decision from utility PUB for the construction of the second phase of Singapore’s Deep Tunnel Sewerage System (DTSS).

CH2M Hill, Arup and a joint venture between Black & Veatch/AECOM were among those shortlisted and which submitted tender documents before the October 24 deadline in 2013.

According to the original schedule, construction on the second phase of Singapore’s DTSS project should have started on January 1 2014. However, a decision on which consultancy will undertake the multi-billion dollar project is expected to be announced over the coming months.

At a cost of US$2.7 billion, DTSS’s first phase was at the time considered one of Asia’s largest engineering projects.

Covering the north and east of the island, the engineering and construction work for the deep sewer tunnels, the link sewers, Changi water reclamation plant (WRP) and the Changi outfall was broken down into nearly 50 main consultants and contractors and 300 sub-contractors and suppliers. Work started in 1997 and was completed in 2008.

The deep tunnel component included 48km of large diameter sewer tunnels built up to 50m below the ground.

A total of eight tunnel boring machines (TBMs) ranging up to 7.2m in diameter were used.

DTSS 1 was constructed with a 100 year design life. A corrosion protection lining was installed to help mitigate the sulphuric acid generated by the high sewage temperatures in Singapore from attacking the lining.

A HDPE primary lining was then used, followed by over 200mm of reinforced concrete for the secondary lining. This was cast against the structural lining of the pre-cast concrete segments.

As well as a shorter, 18km deep tunnel, Phase 2 will also include a new wastewater reclamation plant (WRP) in Tuas.

Singapore is not the only nation undergoing an enormous tunnelling project. Abu Dhabi in the UAE is undergoing a US$1.5 billion Strategic Tunnel Enhancement Programme (STEP). The 40km deep sewer tunnel, up to 80m underground, includes new link sewers and a pumping station.

Meanwhile Qatar’s Public Works Authority – Ashghal – is undergoing the Inner Doha Re-sewerage Implementation Strategy (IDRIS). The 40km long deep trunk sewer programme will include over 70km of lateral inceptor sewers. It will provide a long-term solution to serve the needs of Doha, Al Wakra and Messaieed.

London, too, is undergoing the Thames Tideway project – a 25km tunnel running 80m under the River Thames (see WWi article). Eventually the project should help alleviate pressure off of old Victorian sewers that come under strain with storm water during periods of heavy rain. Labelled the “super sewer”, the project is worth £2.8 billion (US$4.6 billion).

Singapore is already ahead of the pack when it comes to water management. All eyes and ears of the industry are awaiting the decision from PUB on DTSS 2 - a project that will eventually put it even further ahead and create infrastructure that will last 100 years.

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- The full article on DTSSII will appear in the April-May edition of WWi magazine. To sign up for your free copy, click here.

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