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Crazy Rich Singapore | Deep Tunnel Sewerage System, Water Reclamation and the Underground Water Economy begins with a city system almost nobody sees: every time water leaves a sink, shower, toilet or factory, Singapore has to move it somewhere safely, treat it properly and recover as much useful water and energy as possible.
Did you know Singapore’s Deep Tunnel Sewerage System is planned as a 206-kilometre underground network costing about S$10 billion and designed for a 100-year lifespan? The system moves used water largely by gravity toward three centralised water-reclamation plants at Changi, Kranji and Tuas, turning the sewer network into a long-life underground superhighway for water recovery.
That makes “Deep Tunnel Sewerage System Singapore”, “DTSS Singapore”, “Tuas Water Reclamation Plant”, “Singapore sewer tunnel”, “water reclamation Singapore” and “underground infrastructure Singapore” powerful search themes. The Crazy Rich story is not sewage. It is the engineering choice to treat used water as a recoverable national resource rather than something a city simply wants to get rid of.
Crazy Rich Singapore can hide a century of water infrastructure under the city and still let gravity do most of the moving.
Did You Know? DTSS Is a 206-Kilometre Underground Water Network
PUB describes the Deep Tunnel Sewerage System as a 206-kilometre network of deep tunnels and link sewers.
Its job is to collect used water from across Singapore and convey it to large centralised water-reclamation plants.
The network is designed to operate over about 100 years.
That means the engineers are not building for the next election cycle or even the next generation.
They are building for people who are not born yet.
Why Build Deep Tunnels Instead of More Local Sewage Plants?
Older wastewater systems often rely on many pumping stations and treatment plants distributed across a city.
A deep-tunnel system can centralise treatment and reduce the need for numerous intermediate facilities.
The long-term advantages can include:
- smaller surface land footprint;
- fewer pumping stations;
- more efficient centralised treatment;
- greater reliability; and
- better support for water reclamation.
The city gives up expensive underground space so it can recover valuable surface land.
Gravity Is the Secret Energy Saver
The deep tunnels are designed so used water can flow largely by gravity toward the water-reclamation plants.
That matters because pumping enormous volumes of water continuously would consume large amounts of energy.
Gravity is free.
The engineering challenge is shaping the tunnel gradients and network so gravity can do as much work as possible.
One of the richest infrastructure decisions can simply be choosing the right slope.
Phase 1: Kranji to Changi
DTSS Phase 1 was completed in 2008.
It includes:
- a 48-kilometre deep tunnel from Kranji to Changi;
- about 60 kilometres of link sewers; and
- the Changi Water Reclamation Plant.
The Changi plant was built on reclaimed land and designed as a compact, covered treatment facility.
Its initial capacity was 800,000 cubic metres of used water per day and it has since been expanded.
Phase 2 Extends the Network West
DTSS Phase 2 expands the system across western Singapore and into major growth areas.
PUB’s current overview describes about 98 kilometres of Phase 2 tunnels and link sewers serving areas including:
- the western half of Singapore;
- the downtown area;
- Tengah; and
- Jurong Lake District.
This connects directly to Crazy Rich Singapore | Tengah Smart Town, Car-Lite Planning and the Future Housing Economy.
A new town needs roads, rail and power.
It also needs somewhere for every litre of used water to go.
Tunnelling Finished Before the System Did
PUB completed the main tunnelling works for Phase 2 in August 2023.
That did not mean the entire project was complete.
Subsequent work includes:
- corrosion-protection lining;
- link-sewer pipe jacking;
- mechanical and electrical systems;
- flow-control equipment; and
- surface reinstatement.
This is an important infrastructure lesson.
A tunnel breakthrough is visually dramatic.
The operating system still has years of engineering after that moment.
The South Tunnel and Industrial Tunnel
DTSS Phase 2 separates different used-water streams more deliberately.
PUB’s project material describes:
- a 28-kilometre South Tunnel for domestic used water; and
- a 7-kilometre Industrial Tunnel for higher-strength industrial used water.
Separating the streams allows the Tuas Water Reclamation Plant to treat them differently.
That is useful because industrial used water can have very different characteristics from household wastewater.
Why Separate Industrial Used Water?
Industrial water may contain higher concentrations of chemicals, salts or organic material depending on the activity.
Sending every stream through exactly the same treatment train can be inefficient.
Tuas WRP is designed with distinct modules so the treatment process can match the incoming water.
The principle is simple:
do not over-treat what is simple and under-treat what is difficult.
Tuas Water Reclamation Plant: 800,000 Cubic Metres per Day
When operational, Tuas WRP is designed to treat:
- 650,000 cubic metres per day of domestic used water; and
- 150,000 cubic metres per day of industrial used water.
PUB’s current page says the plant is targeted to become operational in 2027.
The domestic treated stream can become feedstock for NEWater production.
The industrial stream is treated to appropriate standards before discharge.
The NEWater Connection
DTSS is inseparable from Singapore’s water-recycling strategy.
Domestic used water reaching the reclamation plants can be treated and further purified into NEWater.
That connects directly to Crazy Rich Singapore | NEWater, Water Technology and the Value of Scarcity.
The sewer therefore becomes the first half of a circular water system.
What leaves the city as used water can return as a strategic water resource.
Tuas Nexus: Water Meets Waste
Tuas WRP is being co-located with NEA’s Integrated Waste Management Facility to form Tuas Nexus.
The goal is to create energy and resource synergies between used-water treatment and solid-waste treatment.
That connects directly to Crazy Rich Singapore | Waste-to-Energy, Tuas Nexus and the Circular Economy.
Instead of treating water and solid waste as separate municipal problems, Tuas Nexus is designed to let the systems exchange useful energy and materials.
Food Waste Can Help Produce More Biogas
At Tuas Nexus, co-digestion of used-water sludge and food waste can increase biogas production compared with treating the streams separately.
That biogas can then support energy generation.
The waste stream becomes a fuel input.
The richer circular economy is not the one with no waste.
It is the one that extracts more remaining value before disposal.
Energy Self-Sufficiency Is the Target
PUB describes Tuas Nexus as Singapore’s first integrated used-water and solid-waste treatment facility intended to be fully energy self-sufficient.
That is ambitious because water treatment and waste processing are energy-intensive activities.
The integration creates opportunities to recover biogas, steam and heat rather than buying all the energy from outside.
Municipal infrastructure starts generating part of the energy needed to operate itself.
Why Corrosion Is a Hundred-Year Problem
Used-water environments are chemically harsh.
Microbiological processes can generate corrosive compounds that damage concrete and metal over long periods.
DTSS Phase 2 therefore uses corrosion-resistant materials and secondary protective linings.
A tunnel designed for a century cannot rely on materials that behave well only during the first decade.
Durability is part of the economics.
Fibre Optics Monitor the Tunnel Structure
PUB’s Phase 2 system uses fibre-optic cables to support real-time monitoring of tunnel structural integrity.
That connects underground civil engineering to sensing technology.
The tunnel is no longer only concrete.
It becomes an instrumented asset capable of reporting information about its own condition.
This connects conceptually to Crazy Rich Singapore | Punggol Digital District, Open Digital Platform and the Smart District Economy.
Isolation Gates Make Maintenance Possible
A 100-year tunnel must eventually need inspection and repair.
DTSS Phase 2 includes isolation gates that allow flows to be diverted so sections can be taken out of service for maintenance.
That is repairability designed into infrastructure.
The best long-life system is not one engineers assume will never fail.
It is one designed so failures can be isolated and repaired.
Air Flow Management Controls Odour
Deep sewers move both water and air.
Poor air management can create pressure and odour problems.
Phase 2 therefore includes purpose-built air-flow and odour-control facilities.
The system has to manage the invisible gas environment above the water as carefully as the water itself.
The Underground City Connection
DTSS shares Singapore’s underground space with rail tunnels, utilities and other deep infrastructure.
That connects directly to Crazy Rich Singapore | MRT Tunnels, Deep Infrastructure and the Underground City.
As the city becomes denser, underground planning becomes a three-dimensional coordination problem.
Every tunnel needs a route through an increasingly crowded subsurface.
Why Land Savings Matter
Centralised deep-tunnel treatment allows older intermediate sewage-treatment facilities and pumping sites to be rationalised over time.
In land-scarce Singapore, freeing surface sites can create enormous economic value.
Infrastructure economics therefore includes the opportunity cost of land.
A deeper tunnel can make the surface city richer.
The Desalination Connection
NEWater and desalination are both weather-resilient water sources.
That connects DTSS to Crazy Rich Singapore | Desalination, Reverse Osmosis and the Water Independence Economy.
Desalination opens the ocean.
DTSS helps close the urban water loop.
Together they reduce dependence on rainfall alone.
Why Industry Depends on the Sewer
Semiconductor plants, food factories, hospitals and commercial buildings all produce used water.
Economic growth therefore increases demand not only for clean water but also for reliable wastewater collection and treatment.
This connects to Crazy Rich Singapore | Semiconductors and the AI Chip Economy.
A factory can stop if clean-water supply fails.
It can also stop if used water cannot be discharged legally and safely.
Why Sewers Are Public Health Infrastructure
Historically, cities with weak sewer systems faced repeated outbreaks of waterborne disease.
Modern sewerage separates human waste from drinking-water systems and dense living environments.
That makes DTSS a public-health system as much as a civil-engineering system.
Its greatest success is that most citizens rarely need to think about it.
Why DTSS Is a Civilisation-Scale Investment
A S$10 billion system designed for 100 years changes the time horizon of public investment.
The people paying for it today will not receive all the benefits.
Future generations inherit the asset.
That is what long-lived infrastructure does.
It moves value through time.
What Students Can Learn from DTSS
Physics
Gravity, fluid flow and pressure determine how used water moves underground.
Chemistry
Corrosion, treatment and industrial wastewater chemistry shape tunnel and plant design.
Mathematics
Tunnel gradients, flow capacity and treatment volumes require large-scale quantitative planning.
Geography
Underground routes must connect growing towns while avoiding other infrastructure.
Civics
DTSS shows why governments invest across generations in systems citizens mostly never see.
Ten Vocabulary Words for the Underground Water Economy
1. Sewerage
The system of pipes, tunnels and facilities used to collect and treat used water.
2. Water reclamation
Treating used water so it can be safely discharged or further purified for reuse.
3. Deep tunnel
A large underground conveyance tunnel built well below ordinary utility depth.
4. Link sewer
A smaller sewer connecting local networks to the main deep tunnel.
5. Gravity flow
Movement of water caused by elevation differences rather than mechanical pumping.
6. Corrosion protection lining
A protective internal layer designed to resist chemical or biological attack on tunnel surfaces.
7. Water reclamation plant
A facility treating used water before reuse or safe discharge.
8. Biogas
Fuel gas generated from biological breakdown of organic material.
9. Co-digestion
Treating different organic waste streams together to improve digestion and energy recovery.
10. Tuas Nexus
Singapore’s integrated used-water and solid-waste treatment complex combining Tuas WRP and the Integrated Waste Management Facility.
Frequently Asked Questions
How long is the full DTSS network?
PUB describes it as a 206-kilometre network of deep tunnels and link sewers.
How much does DTSS cost?
Around S$10 billion across the full system according to PUB’s current overview.
How long is it designed to last?
About 100 years.
When will Tuas Water Reclamation Plant operate?
PUB’s current Tuas WRP page says it is targeted to become operational in 2027.
What happens to treated domestic used water?
It can be further purified to become NEWater, closing part of Singapore’s water loop.
Helpful Reading Across the Singapore Graph
- Crazy Rich Singapore | NEWater, Water Technology and the Value of Scarcity
- Crazy Rich Singapore | Waste-to-Energy, Tuas Nexus and the Circular Economy
- Crazy Rich Singapore | MRT Tunnels, Deep Infrastructure and the Underground City
- Crazy Rich Singapore | Desalination, Reverse Osmosis and the Water Independence Economy
References and Current Sources
- PUB, Deep Tunnel Sewerage System, current 206km network, S$10b cost and 100-year design overview.
- PUB, Tuas Water Reclamation Plant, current 2027 operational target and treatment capacities.
- PUB, DTSS Phase 2 Conveyance System, current tunnel, link sewer, isolation gate and structural-monitoring details.
- PUB, PUB Completes Tunnelling Works for DTSS Phase 2, technical Phase 2 facts.
Crazy Rich Singapore Puts the Circular Economy Underground
Most cities think of sewers as disposal infrastructure.
Singapore increasingly treats them as the front end of water recovery.
Did you know? One of Singapore’s richest water assets is a tunnel nobody wants to visit—because it quietly carries tomorrow’s NEWater through the dark beneath today’s city.