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Singapore Tunneling Project Begins

Industrial area of Jurong, which is one of the several regions of Singapore
Jurong is one of several regions of Singapore that will be open to additional development once the deep tunnels are constructed and existing pumping stations and conventional treatment plants are phased out. Wikimedia Commons/Calvin Teo

Singapore embarks on the second phase of a massive civil engineering project that will dramatically increase the use of recycled water.

July 1, 2014— A feasibility study and preliminary design work are under way on the second phase of the Deep Tunnel Sewerage System (DTSS), a massive civil engineering project in Singapore. This phase of the project comprises 30 km of deep tunnels, 70 km of linking sewers, a new water reclamation plant, and a deep sea outfall. The project will dramatically change how water is provided in the island country, which has a population of 5.4 million.

A joint venture of engineering firms Black & Veatch, of Overland Park, Kansas, and AECOM, of Los Angeles (B&V+AECOM) was recently selected as the lead consultant on the project. In addition to the feasibility study and preliminary design work, the team will provide program management as the project progresses. The first phase of the project, which serves the northern and eastern parts of the island, was completed in 2008. The second phase will serve downtown Singapore and areas to the west.

“This is a once-in-a-life time engineering challenge. From a pure scale and numbers perspective, the project is vast,” said Geoff Piggott, P.E., CPEng, the project director of DTSS Phase 2 for B&V+AECOM, in written responses to questions posed by Civil Engineering online. “If you can manage to wrap your head around the sheer scale of the project, what is incredibly exciting are the goals that underlie this project. This will not be a conventional approach. The innovation that underlies this effort will make the project cost-effective and deliver a range of sustainable benefits for Singapore.”

The DTSS project is part of the ambitious NEWater program by the Singapore Public Utility Board (PUB). (Read “Singapore Plans Two More Reuse Plants, Increasing Its Reliance on Reclaimed Water,” in Civil Engineering magazine, August 2008, pages 33 to 35.) PUB’s goal is to greatly increase the availability and use of recycled water while minimizing the amount of scarce land area devoted to infrastructure. The aim is to eventually meet as much as 55 percent of customer demand with recycled water, Piggott noted.

“DTSS allows every drop of used water to be collected, treated, and further purified into NEWater at the centralized water reclamation plants (WRPs),” Piggott said.

The project includes the new Tuas Water Reclamation Plant (TWRP), which will have a capacity of 800 million liters/day, Piggott said. The plant will incorporate advanced technologies to treat water to very high standards, and will be colocated with a new Integrated Waste Management Facility. “There are great opportunities to harness synergies from having used water and solid waste treatment located side-by-side. We are exploring technologies that will reduce energy consumption and over time be net energy-neutral in terms of treatment processes,” Piggott said.

Tuas is also home to a 136,380 m3/d water desalination facility, the largest in the world at the time of its opening in 2008. Desalination is another important element in Singapore’s multifaceted approach to water supply. (Read “The Singapore Solutions,” in Civil Engineering magazine, January 2007, pages 62 to 69.)

Map of the first and second phase of the Deep Tunnel Sewerage System

While the first phase of the Deep Tunnel Sewerage System
focused on the north and east, the second phase concentrates on
the west and city center. © PUB, Singapore’s National
Water Agency

Like those plants, the new TWRP will be located at the shoreline. “The concept of the DTSS is to use deep tunnel sewers to convey used water by gravity to centralized water reclamation plants located at the coastal areas,” Piggott said. “When fully completed, DTSS will result in a 50 percent reduction in land taken up by used water infrastructure, freeing land for other high-value development.” 

The project will enable Singapore to phase out pumping stations and conventional treatment plants at Ulu Pandan and Jurong, Piggott said. That will free the prized land there for development. Singapore is highly urbanized, with a robust trade economy that emphasizes manufacturing and financial services. “Singapore is land-scarce and its population and economy continue to grow,” Piggott pointed out, adding that a government report titled A Sustainable Population for a Dynamic Singapore, 2013, estimates that Singapore’s total population could range between 6.5 and 6.9 million by 2030.

“Through integrated water management, PUB has successfully closed the ‘water loop’ and manages the whole water cycle, from rainwater collection to the purification and supply of drinking water, to the treatment of used water and its reclamation into NEWater, Singapore’s own brand of high-grade reclaimed water,” he said.

Piggott said that it’s too soon in project planning to discuss the tunnels of the project in great detail, though he noted that they are likely to be similar to those constructed in the first phase, which were as much as 6 m in diameter and located as much a 70 m below the surface to achieve the necessary gravity flow.

“There were a number of lessons learned from Phase 1 tunneling that can be incorporated into how Phase 2 is delivered,” Piggott said. “However, the tunneling for Phase 2 of DTSS ...will be driven in quite different geology to that in Phase 1. This will probably entail more extensive site investigation studies to increase resolution on ground conditions and reduce uncertainties ahead of the commencement of tunneling.”

The team plans to conclude the feasibility study and preliminary design work by 2016, and construction is slated to begin soon thereafter.



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