EXISTING BULK WATER SUPPLY INFRASTRUCTURE
BACKGROUND INFORMATION FOR WSDP
NOVEMBER 2005
BULK WATER SUPPLY INFRASTRUCTURE
1.
WATER DEPARTMENT: INTRODUCTION
The CMC Administration of the CCT provides the bulk supply of treated water to the six
Administrations within the CMA as well as to other Water Services Authorities outside the CMA. In
order to carry out this function, it abstracts water from various water sources, purifies the water to a
potable standard at its water treatment plants, and then stores or conveys the water to points of
supply within or outside the CMA.
The CCT owns and operates the following water treatment plants (WTP):
NO.
WATER TREATMENT PLANTS
THEORETICAL
TREATMENT
CAPACITY
(Mℓ/day)
20
1
Witzands (softening plant)
2
Silwerstroom
9
3
Kloof Nek
17
4
Constantia Nek
3
5
Faure
500
6
Steenbras
150
7
Wemmershoek
270
8
Voëlvlei
273
9
Blackheath
400
10
Brooklands
6
11
Somerset West
15
12
Strand (currently, not operational)
2
13
Albion Spring
TOTAL
4,5
1 669,5 Mℓ/d
The sustainable treatment capacity for a peak week may be less than the figures portrayed in
the table due to operating circumstances and conditions (Total approx 1500ml/d).
The CCT also owns and operates numerous large storage reservoirs and pump stations. In
addition to the above, the CCT also owns and operates Rockview Aqueduct.
The bulk supply system consists of many large diameter pipelines. The pipelines themselves
will not be described individually, but rather as elements of the WTP’s.
The quantity water leaving each WTP, Reservoir and Pump Station is monitored by flow meters.
All points of supply on the bulk pipelines are metered and monitored.
2.
WATER TREATMENT PLANTS (WTP)
2.1
FAURE WATER TREATMENT PLANT
The Faure WTP is situated just outside the Cape Metropolitan Area between the settlements of
Faure and Firgrove. The WTP was designed for construction in two stages, the first stage which
is complete has a capacity of 500 Mℓ/day. The capacity of Stage II is still to be decided and the
implementation date will be determined by the average peak week demand in the CMA and
future infrastructure requirements and phasing.
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Raw water is conveyed to the WTP via two large diameter pipelines, namely:
(A)
A 12 km long 1 830/1 875 mm diameter pipeline from the Stellenboschberg tunnel
portal supplying water from the Riviersonderend/Berg/River Government Water Scheme
(RSE Scheme); and
(B)
A 18 km long 1 800/1 700 mm diameter pipeline from the Lower Reservoir of the
Steenbras Pumped Storage Scheme, supplying water transferred from the Palmiet
River. This water is pumped to Faure Water Treatment Plant by means of Firlands
Pump Station.
The distribution pipeline exiting Faure WTP is a 23 km long 2 400/1 830 mm diameter pipeline
that links up with the existing bulk supply system. Figure 1 shows the layout of the water
supply infrastructure to and from Faure WTP.
The treatment process at Faure WTP has to cater for water from the Riviersonderend and
Palmiet River. The water treatment process consists of raising the pH of the raw water with
lime to a suitable level for coagulation with ferric sulphate, taste and odour removal with
powdered activated carbon, horizontal flow sedimentation, declining rate rapid gravity sand
filtration, stabilisation with lime and carbon dioxide and disinfection with chlorine. Sludge is
dewatered and thickened by means of centrifuges before being trucked off site to a landfill
waste dump.
2.2
BLACKHEATH WTP
Blackheath WTP is situated near Kuils River and has a maximum design capacity of
400 Mℓ/day.
Raw water from the Stellenboschberg Outlet is conveyed to the Blackheath WTP by means of a
17,8 km long 1 500 mm diameter prestressed concrete gravity pipeline with a design capacity of
400 Mℓ/day. Water from the water treatment plant flows to the nearby Blackheath Upper
Service Reservoir with a capacity of 48,2 Mℓ or the Blackheath Lower Service Reservoir with a
capacity of 540 Mℓ. From there, water is distributed through two 1 500 mm diameter prestressed
concrete pipelines with lengths of 20,5 km and 13 km. Figure 1 shows the layout of the water
supply infrastructure around Blackheath WTP.
The treatment process consists of coagulation with aluminum sulphate and taste and odour
control with powder activated carbon preceding settlement in horizontal flow sedimentation
tanks, followed by rapid sand filtration, stabilisation with lime and carbon dioxide and final
disinfection with chlorine.
2.3
WEMMERSHOEK WTP
The Wemmershoek WTP which was completed in 1958 is located at the base of Wemmershoek
Dam. The maximum output from the WTP is approximately 270 Mℓ/day. A pre-treatment
plant was added in 1980 to allow a supplementary supply of up to 140 Mℓ/day from the RSE
Scheme to receive final treatment in the main plant.
Raw water is conveyed to the Wemmershoek Water Treatment Plant from the RSE Scheme
through a 18 km long 1 100 mm diameter steel pipeline with a design capacity of 140 Mℓ/day.
Treated water from Wemmershoek Water Treatment Plant is conveyed to Tygerberg Service
Reservoir through a 48,7 km prestressed concrete pipeline. The first 26,5 km of the pipeline
has a diameter of 1 525 mm whilst the remaining 23,2 km has a diameter of 1 220 mm. The
pipeline is designed to deliver a peak flow of 227 Mℓ/d to Tygerberg Reservoir.
The 1 525 mm diameter pipeline has a design capacity of 318 Mℓ/d. This pipeline also supplies
an offtake to Paarl and Wellington 5 km downstream of the Water Treatment Plant. Figure 1
shows the layout of the water supply infrastructure around Wemmershoek WTP.
The water treatment process at the treatment comprises coagulation, flocculation,
sedimentation, filtration and stabilisation.
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2.4
VOËLVLEI WATER TREATMENT PLANT
Voëlvlei Water Treatment Plant is located near Gouda and adjacent to Voëlvlei Dam. The
maximum output from Voëlvlei WTP is 273 Mℓ/d.
Raw water is pumped to Voëlvlei Water Treatment Plant from the dam through a 1 500 mm
diameter 0,6 km long pre-stressed concrete pipeline.
Treated water is pumped from the 9,1 Mℓ clearwell at Voëlvlei Water Treatment Plant by
means of a high pressure pump station with variable speed motors through an 80 km long
1 525 mm diameter pre-stressed cement pipeline to Plattekloof Reservoir. Figure 1 shows the
bulk supply pipeline from Voëlvlei WTP.
The water treatment process consists of coagulation, taste and odour control with powder
activated carbon, vertical flow settlement, filtration and chlorination.
2.5
STEENBRAS WATER TREATMENT PLANT
The Steenbras Water Treatment Plant is situated on the Cape Town (West) side of the
Hottentots Holland Mountains. The water treatment plant was completed in 1946 and has a
capacity of 150 Mℓ/d.
The water treatment plant is supplied with raw water from Steenbras Lower Dam via a 752 m
long tunnel through the Hottentots Holland Mountains.
Potable water from the Steenbras Water Treatment Plant is distributed through 3 bulk pipelines,
namely:
(A)
the Steenbras 840 mm diameter main: This pipeline is a bitumen lined steel pipeline
feeding Newlands Reservoir with the booster pump station at Garlandale. The
capacity of the pipeline is 91 Mℓ/d when Garlandale pump station is utilised. The
capacity is 50 Mℓ/d without the booster pump station being operational.
(B)
the Steenbras 815 mm diameter main: This is a cement mortar lined steel pipeline
that supplies Newlands No. 1 and Wynberg No. 2 Reservoir through a 915 mm
diameter branch pipeline. The pipeline is 53 km long and was designed to deliver
45,5 Mℓ/day. With Kildare Booster Pump Station operating the capacity is increased
to 91 Mℓ/day.
(C)
the Steenbras 760 mm diameter pipeline: This is a 63 km long cast iron pipeline
from Steenbras Water Treatment Plant to the City of Cape Town’s Molteno
Reservoir. Delivery directly to Molteno has been discontinued and the pipeline is
currently isolated and used as a distribution pipeline.
Figure 1 shows the layout of this water supply infrastructure.
The treatment process used at Steenbras Water Treatment Plant consists of coagulation,
flocculation, horizontal flow settlement, gravity sand filtration, stabilisation and chlorination.
2.6
BROOKLANDS WATER TREATMENT PLANT
Brooklands Water Treatment Plant is situated close to Simon’s Town. The new treatment plant
was completed in 1974 and has a treatment capacity of 6 Mℓ/day.
The raw water is obtained from the Lewis Gay and Kleinplaas Dams. The treated water is fed
directly into the distribution system of South Peninsula Municipality. See Fig 2.
The treatment process used is coagulation, flocculation, sedimentation, filtration and
chlorination.
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2.7
KLOOF NEK WATER TREATMENT PLANT
Kloof Nek Water Treatment Plant was completed in 1938 and is situated above Camps Bay.
The water treatment plant has a capacity of 17 Mℓ/day. Raw water is obtained from the
Hely-Hutchinson and Woodhead Dams. The treatment process consists of coagulation,
flocculation, sedimentation, filtration, stabilisation and chlorination. See Fig 3.
2.8
CONSTANTIA NEK WATER TREATMENT PLANT
Constantia Nek Water Treatment Plant is situated at Constantia Nek. It was completed in
1934 and has a treatment capacity of 3 Mℓ/day.
Raw water is obtained from the Victoria, Alexandra and de Villiers Dams situated on the top of
Table Mountain. Treated water is fed directly into the reticulation system of South Peninsula
Municipality. See Fig 3.
The treatment process consists of coagulation, flocculation, sedimentation, filtration,
stabilisation and chlorination.
2.9
ATLANTIS
The Atlantis Water Undertaking consists of the following components which have been built
since the start of development of Atlantis in 1975 through to 1999.
*
*
*
*
*
*
Silwerstroom wellfield, treatment plant and reservoir
Silwerstroom pumping main, 300 mm diameter and 17,8 km long with 4 pumping stations,
delivering up to 8,6 Mℓ per day to the Pella Reservoirs.
Witzands wellfield, water softening plant and balancing tank.
Witzands pump main, 400 mm diameter 13,8 km and with three pumping stations, delivering
up to 22 Mℓ per day to the Hospital and Pella Reservoirs.
Pella Reservoirs holding 10 Mℓ and 40 Mℓ serving Atlantis, Mamre and Pella residential
areas.
Hospital reservoirs holding 10 Mℓ and 20 Mℓ serving Atlantis industrial area.
The Atlantis system is currently being upgraded in the Atlantis Water Augmentation Scheme
and upon completion will include the following:
(A)
Gravity main 500 mm diameter, 11,6 km in length from Melkbos pipeline to Atlantis
Water Treatment Plant.
(B)
Pumping main 450 mm diameter, 13,8 km in length from Atlantis Water Treatment
Plant to Pella Reservoir.
(C)
Pump stations at Atlantis Water Treatment Plant and at Hospital Reservoir. This
includes replacement of existing pumping plant and providing dedicated pumping to
Pella and Hospital Reservoir via independent pump stations with standby facilities.
(D)
Alterations to the 400 mm pump main from Witzands to Hospital Reservoir and from
Hospital Reservoir to Pella.
The water treatment process consists of:
(A)
(B)
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At Silwerstroom Water Treatment Plant: pressure sand filters, pH adjustment with
caustic soda and gas chlorination.
At Witzands Water Treatment Plant: 50% of the raw borehole water flow through a
softening plant. The outgoing flow is pH adjusted with caustic soda and then
chlorinated. The balance of demand is made up by drawing from the Voëlvlei
pipeline via Melkbos Reservoirs.
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2.10
ALBION SPRING
Albion Spring is situated in Rondebosch. See Fig 3. It was completed in 1890 and has a
treatment capacity of 4,5 Mℓ/day.
Raw water is obtained directly from the Albion Spring, the pH is adjusted by aeration, the water
is chlorinated and then pumped directly into the distribution system of the City of Cape Town.
2.11
SOMERSET WEST AND STRAND WATER TREATMENT PLANTS
The Somerset West Water Treatment Plant is situated in Helderberg Nature Reserve above
Somerset West. It has a treatment capacity of 15 Mℓ/day.
Raw water can be conveyed from the Lourens River to the water treatment plant by means
of:
-
gravity feed from Lourensford Estate
a rising main from Radloff Park
Raw water is also pumped to the water treatment plant from boreholes located adjacent to the
Lourens River.
Treated water is either gravity fed to Helderberg Municipality or pumped up to Hillcrest
Reservoir owned by Helderberg Municipality.
The treatment process is slow sand filtration and chlorination.
The Strand Water Treatment Plant is located near the van der Stel Station in Strand and has a
treatment capacity of 2 Mℓ/day.
Raw water is gravitated from Lourens river, treated and then fed directly into the reticulation
system of Helderberg Municipality. The treatment process consists of slow sand filtration, pH
adjustment with lime and chlorination.
3.
BULK SERVICE RESERVOIRS
The main characteristics of the CCT’s Bulk Water Service Reservoirs are listed in the table
below:
NO.
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SERVICE RESERVOIR
1
Blackheath Upper
CAPACITY @ FSL
(Mℓ)
48,20
FSL
(m) RL
174,50
DEPTH
(m)
7,28
2
Blackheath Lower
537,60
110,60
11,84
3
Constantia Nek
3,38
230,97
7,32
4
Monterey
23,35
189,06
6,39
5
Newlands Upper
132,60
138,20
7,63
6
Plattekloof
583,60
110,97
12,23
7
Tygerberg No. 1
33,44
110,57
7,64
8
Tygerberg No. 2
275,90
110,57
12,19
9
Wynberg No. 1
8,64
118,19
3,50
10
Faure
614,20
110,68
12,22
11
Glen Garry
149,20
140,20
6,88
12
Melkbos No. 1
20,00
100,00
11,75
13
Melkbos No. 2
20,00
100,00
11,75
14
Witzands (boreholes)
0,250
60,00
2,00
15
Pella No. 1
10,00
241,95
9,69
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NO.
SERVICE RESERVOIR
CAPACITY @ FSL
(Mℓ)
40,00
FSL
(m) RL
239,4
DEPTH
(m)
6,7
16
Pella No. 2
17
Hospital No. 1
10,00
193,50
8,2
18
Hospital No. 2
20,00
193,50
9,0
19
Midlands
10,00
175,00
9,08
20
Silwerstroom (boreholes)
1,00
25,52
5,82
Figure 1 shows the geographical location of the large Service Reservoirs with respect to the
water treatment plants and bulk supply system.
4.
PUMP STATIONS
The main characteristics of the pump stations are listed in Table 1 in Annexure “A”.
5.
WATER TREATMENT DATA
Information on the treatment process, chemical dosages and raw and treated water quality for
every water treatment plant is given in Table 2 in Annexure “A” (Information is illustrative only).
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ANNEXURE “A”
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PUMP STATIONS
PUMP STATIONS
ATLANTIS
NO. OF
PUMPS
Softening Plant Raw
Water
Softening Plant
Product Water
Witzands No. 1
3
FLOW PER
PUMP UNIT
(Mℓ/day)
8,4
HEAD
(m)
50
RATED MOTOR
POWER (kW)
EACH
55
REMARKS
3
9,1
8
15
3
7,8
120
185
Witzands No. 2
3
7,8
120
185
Witzands No. 3
2
8,6
71
160
Silverstroom No. 1
Weir
Silverstroom No. 2
2
6,0
18,5
18
2
5,7
110
110
Silverstroom No. 3
2
5,7
110
110
Silverstroom No. 4
2
5,7
110
110
Proposed Witzands
“A”
Proposed Witzands
“B:
3
14,4
166
410
3
13,9
240
575
NO. OF
PUMPS
HEAD
(m)
1
1
1
FLOW PER
PUMP UNIT
(Mℓ/DAY)
4,3
4,3
23,0
77,4
RATED MOTOR
POWER (kW)
EACH
56
8,40
330
1
1
1
19,0
19,0
91,0
80,0
86,0
104,0
250
250
1 400
Pumping in parallel –
21,1 Mℓ /day
Variable speed motor
Kildare Road
1
1
65,4
65,4
43,6
87,2
400
400
Variable speed motor
Pumping in series –
69,0 Mℓ/day
Albion Spring
1
4,8
100,00
90
Newlands 535
1
50,0
50,0
373
Voëlvlei Low Lift
3
2
5
1
3
1
68,1
79,5
68,1
22,7
60-300
24,0
29,0
120,0
125,0
110
306
429
1 313
429
1 700
1
1
23
23
90
90
400
400
PUMP STATIONS
Wynberg No. 1
Wynberg No. 2
Monterey
Garlandale
Voëlvlei High Lift
Firlands
Wynberg No. 3
REMARKS
Pumping in parallel –
7,2 Mℓ/day
Variable speed motor
Variable speed motor
Variable speed motor
Maximum 300
Mℓ /day with 3 pumps
To be commissioned
in March 1999
TABLE 1
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TABLE 2
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