1

Tan Chee Hoon

Senior Principal Engineer, WRN

Planning Used Water Network

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Topics

• Overview

• Used Water Network Planning

• Projects and Schemes

• Design of Used Water Network

• Rehabilitation of Sewers

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Used Water Network Overview

#Used water is collected separately from rain water

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Used Water Sources

• Domestic - generated by human

activities such as cooking, bathing and

washing.

• Industrial - generated mainly from

commercial activities and factories and

generally called trade effluent.

• Extraneous Infiltration & Inflow

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Water Reclamation (Network) Department

Mission Statement

To convey all used water for reclamation cost-

effectively and reliably

Function • Plan, upgrade, operate and maintain the public Used

Water Network System

• Regulation of sewerage and sanitary facilities by

private developers

Role in the Closed Water Loop

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Water Reclamation Network & their Catchments

Kim Chuan WRP (decommissioned in Feb 2008)

Bedok WRP (decommissioned in Apr 2009)

Water Reclamation plants

Sewage pumping stations

Ulu Pandan WRP

Seletar WRP (decommissioned in Aug 2011)

Jurong WRP

Kranji WRP

Singapore was historically divided into 6 catchments

• 3384 km of sewers

• 113 km of pumping mains

• 78 pumping stations

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Component Length

(km)

Max Dia

(m)

Depth

(m)

North 38 6.0 25-49

Spur 10 3.3 25-49

Link Sewers 60 3.0 10-25

Total 108

Deep Tunnel Sewerage System (DTSS)

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Used Water Network Planning

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Six Sewerage Catchments

Structure of Catchment Planning

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Used Water Network Planning

(1) Planning for :

• Provision New network for future developments

• Upgrading Existing network and pumping station/mains

• Rehabilitation Sewer/ pumping main

• Extension Relief and diversion within existing network

Land Use Plan Catchment Plan

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Project Planning and Regulatory Works

(2) Cost estimation and submission of plan cost paper

(3) Control and approve proposal for new network

facilities for development projects

• Development Agencies (URA, HDB, JTC, EDB…)’s

consultation/plan submissions for Infrastructure or

Development projects

• QP’s DC plan/BP plan submissions for private building

projects

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Catchment Planning:

• Maintain knowledge of the overall reticulation system, flow distributions and design sewer capacity in the catchment

- Catchment Sewerage Network Map

• Update changes in land use, development schedules and flow projections

- URA 5-year Master Plan on Land-use

- Infrastructure Development Consultation by Development Agencies (URA, HDB, JTC, EDB…) on Specific Land Use

• Control provision of new sewers, new connection to existing sewers and provision of interim facilities

- Development Control (DC) Plan and Building Plan (BP) submissions

• Update development/sewer proposals in Sewerage Mapping System

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Projects and Schemes

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Sewerage Works for Additional Reclamation Areas Off

Tuas Hockey Stick

Objective

To extend sewerage facilities to serve Tuas View area

Estimated Cost

$80 million

Project Detail

• 30 km of sewers

• 1 km of pumping main

• 2 pump sumps

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Objective

To lay sewers to serve new developments in Marina South, Pasir Ris/Tampines

areas, and phase out Nee Soon Pumping Station (PS)

Estimated Cost

$199 million

Project Details

• Lay 27km of sewers

• Phase out 1 PS

Project Duration

2007 to 2013

Marina South & Pasir Ris/Tampines Sewerage Schemes

Marina South

Pasir Ris/Tampines

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Jurong East Sewerage Schemes

Objective

To lay sewers to serve Jurong

Eastern catchment & Jurong Lake

District; and phase out 4 pumping

stations

Estimated Cost

$230 million

Project Details

• Lay 21.9km of sewers

• Construct 2 lift stations

• Phase out 4 pumping stations

Project Duration

2010 to 2015

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Design of Used Water Network

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Involves 2 Main Steps :

•Projection of peak Used Water Flow generated

•Designing Adequate Hydraulic capacity

Design of Used Water Infrastructure

Capacity

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Determination of Design Flow

Network infrastructure to convey peak used water flow

Projected Flow = Area (equivalent) Population

X Per Capita Average Flow

X Peaking Factor

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Domestic Population Densities For Flow Projection

Land Use Population Density

Person per Ha

Public Housing

Less than 100 ha

100 – 500 ha

501 – 1000 ha

More than 1000 ha

740

500

400

300

Private

High Rise – PR = 1.4

PR = 1.9 – 2.8

PR = 5

Landed

400

740

1300

250

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Land Use Population Density per Ha

Commercial

Hotels

Shopping Centres

Offices

2200

3300

2800

Light Industries 210

Medium / Heavy Industries 130

Hospitals 680

Open Space e.g. Parks 12

Agriculture 25

Commercial and Industrial Population

Densities Equivalent for Flow Projection

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AVERAGE FLOW PER CAPITA

AND PEAK FACTOR

(Present) Ultimate

Ave. Flow per capita

(lcpd) Peak Factor

HDB Flats (167)

230 2.5 to 3

Landed

Property

(250)

345 2.5 to 3

Commercial

and Industrial

(250)

345 2.5 to 3

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Design of Sewers

Hydraulic Design

Types of Sewer Pipes

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gDSD

r

D

kgDSv

2

51.2

7.3log22

Classic Hydraulic Design

Colebrook-White equation for a sewer’s flow

velocity

[l/s] discharge Q

gradient hydraulic S

[m]sewer ofdiameter D

relate toused are Charts Design

/m10x 1.41 viscositykinematic r

m10x 0.6 t coefficien roughness surface k

10m/s onaccelerati nalgravitatio g

[m/s]flow of velocity vwhere

, full flowing pipe ConcreteFor

26-

3

2

s

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Sewer Network Planning

Network Planning Module (being Developed)

ArcGIS

CATCHMENT PLANNING INFORMATION MAPS

(CPIM)

migrate

Sewer Modeling Module (Pilot by 2013)

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Network Planning and Design with Operational

Inputs

Network

Operation

Analysis

Module Network

Design

Module

(DeMo)

Sewer

Modeling

Module

(SeMo)

ArcGIS

Database (Sewer Network, Planning &

Land-use parameters, Level,

Assets, Models, Options)

eg.

InfoSWMM (Network Model &

Calibration)

eg.RDII

Analyst (Identification of

surcharge issues)

eg. Designer (Sewer network Design)

eg. ICM Live (Operational Forecasts)

Network

Level

Sensors (Rainfall &

Surcharge

sensors)

ReNe Remote Network

Monitoring

System

Monitored

Alarms

Monitored Flows & Levels

Forecasted Alarms

Existing WRN system

Proposed

Modules

CMS (Network and

DTSS Flow

Monitors)

Network

Planning

Modules

(NeMo)

CPIM Sewer Capacity

Checking & Classical

Sewer Sizing

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#Practical Hydraulic Design

Other Considerations

(a) Minimum diameter, D 200 mm

and at food establishmentD 250 mm

(to reduce blockage)

(b) Flow Velocity to transport suspended solids with little

sedimentation while not causing erosion

v > 0.9m/s for self-cleaning velocity

v < 2.4m/s to limiting scouring

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Vitrified Clay (VC) pipes - EN 295

Reinforced Concrete pipes - SS183

•for diameters < 900mm internal sacrificial

layer of 38mm provided

•for diameters > 900mm, pipes lined with

PVC /HDPE

Types Of Pipes Used For Sewers

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Permit inspection, cleaning and change

of flow direction

• Precast rings with concrete surround

from 1050 dia. to 1800 dia.

• Standard cast iron manhole cover

• Spaced not more than 120m apart.

For sewers > 1800 dia., spacing may

be increased to 500m

Manhole Cover

Chamber

Ring Cast

In-

Situ

Base

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Back Drops and Vortex Drops

Difference in

invert levels

Sewers

diameter

≤ 450 mm

D ≤6m

Backdrop

D > 6m

Vortex Drop

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Sewer Rehabilitation

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Cracks Joint

s

Tree-root Intrusion Cracked Pipe Joint breakage

Long Term Problems in Sewers

Sewers deteriorate due to:

• long-term wear and tear

• corrosive gases within the sewers

• progressive ground movement

• adjacent construction

• intruding tree roots

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Sewer Rehabilitation

After Before

Sewers can be rehabilitated to：

• Restore their structural integrity

• Extend their lifespan

• Reduce infiltration & exfilitration

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Rehab Method Description Before & After

Cured-in-place pipe (CIPP) –

The process involves the

insertion of a flexible lining

impregnated with a

thermosetting resin into a

cleaned pipe via inversion. (hot

water or steam).

Spiral Wound Lining (SWL) – The process involves winding interlocking PVC strips in a spiral pattern into the existing pipe.

Fold and Form (F&F) – The process involves the expansion (steam) of a continuous coil of formulated PVC pipe to form a tight fitting liner (when cooled) within the existing host pipe.

Types of Sewer Rehabilitation Liner

Cured-in-place-pipe

lining

Spiral Wound Lining

Fold & Form lining

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Before After

Equipment for Spray Coating

Rehabilitation of Manholes

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Sewer Rehabilitation Programme

Estimated Cost

•$150 million (sewer)

•$68 million (SDS)

Project Detail

Rehabilitate 600 km

of sewers and

drainlines

Project Duration

2006 to 2012

SINGAPORE RIVER

STAMFORD RIVER

ROCHOR RIVER

KALLANG RIVER

PELTON RIVER

GEYLANG RIVER

Objective

To rehabilitate the sewers and sanitary

drainlines in Marina Reservoir Catchment

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Rehabilitation Of Sewerage Network System – Phase 4

Sewers and Mains

Objective

To rehabilitate the

sewers (> 30 yrs)

and pumping

mains (> 20 yrs)

islandwide

Project Details

• 1,130 km of sewers

• 50 km of mains

Project Duration

2009 to 2014

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Thank You