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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 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
(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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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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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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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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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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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