Water Demand Sepang

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ALTERNATIVE WATER SUPPLY SCHEME FOR KUALA LUMPUR

INTERNATIONAL AIRPORT (KLIA), SEPANG, SELANGOR.

By

Ir. Dr. Hasnul M Salleh1, Ir Teo Koon Hau2Ir and Zulkiflee Abd Hamid3

Keywords: Off river storage, intake works, river gate, pumping station, reservoir,

diversion culvert, outlet work, spillway and draw off tower

1.0 Background

Kuala Lumpur International Airport (KLIA) is located about 50km from the capital city

of Kuala Lumpur and about 25km from the Administrative Capital of Putrajaya. At

present, the water supply to KLIA is provided solely by Sungai Semenyih water

treatment plant (WTP), which in the past has experienced failure that leads to

disruption of water supply for 3 days.

In view of the importance and sensitivity of KLIA, the Government of Malaysia has

implemented a project as an alternative water supply system to KLIA to mitigate the

risk of water supply disruption to KLIA, which will have detrimental effects on the

Country’s image, political aspect and economical aspect. This project is to optimize

storm water as an alternative to conventional raw water source ie either direct

abstraction from the river or from the dam and reservoir.

The main objective of this project is aimed at sourcing new water supply to cater for

KLIA’s demand. However, the water demand of KLIA surrounding area is also being

studied, so that, the spare supply from the source can be channeled to the

surrounding areas. The surrounding areas of KLIA being studied are the districts of

Kuala Langat and Sepang. This is because the Semenyih WTP is already operating

at its maximum capacity and the proposed Langat II WTP with raw water from

Pahang will not be operational until at least Jun 2014. As such, any additional source

will provide relief to the Semenyih WTP.

1Director General , Water Supply Department, Ministry of Energy, Green Technology and Water (Superintending Officer of Project) 2 Senior Engineer, SMHB, Sdn. Bhd. 3 Director, SMHB, Sdn. Bhd.

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2.0 Demand Projection for Kuala Langat and Sepang Districts

Demand projections for the Kuala Langat and Sepang districts are based on

available existing study reports.

The details of the demand projections from Langat 2 study report for the districts of

Kuala Langat and Sepang are as summarized below:

Year Demand (Mld)

Kuala Langat Sepang Total

2010 135 195 330

2020 201 323 524 Langat II: Preliminary Engineering Design Report for Langat II Scheme: KDEB (March 2005)

The main source of supply to Kuala Langat and Sepang districts is the Semenyih

Plant. Other sources supplying the districts are listed below:

District Source Supply (Mld)

Kuala Langat Bkt. Tampoi

Sg. Selangor – Bukit Badong

32

18

Sepang Salak Tinggi 11

Note: Salak Tinggi WTP presently producing 4-5 Mld only.

Assuming that the above plants will continue to supply water at the same quantum to

Kuala Langat and Sepang Districts, the balance of water required from the existing

Sg. Semenyih plant can be summarized as follows:

District Year Increase in

Demand 2010 2020

Kuala Langat 85 151 66

Sepang 184 312 128

TOTAL 269 463 194

Currently the Semenyih WTP is supplying close to 260 Mld to Kuala Langat and

Sepang Districts. However, it is important to note that the existing Sg. Semenyih

WTP is already operating near its maximum capacity of 636 Mld (140 mgd). This

plant can only be expected to support increasing water demands in Kuala Langat and

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Sepang if it is relieved of its role in serving other areas such as the districts of

Petaling and Hulu Langat in a timely manner.

Significant relief for the Sg. Semenyih water treatment plant is only expected on

completion of the ongoing Langat 2 works which is expected to be able to deliver

treated water to the existing Bukit Dengkil reservoirs in late 2014 due to the delay in

the Pahang-Selangor Interstate raw water transfer project. It is envisaged that

Selangor and Wilayah Persekutuan Kuala Lumpur and Putrajaya will experience

water shortages that are expected to progressively worsen until 2014.

Partial relief for the Sg Semenyih plant in the short term from the existing Sg.

Selangor plants is also doubtful since supply available from the Sg Selangor WTPs is

extremely limited and needs to be distributed to other demand centres as well. It is

therefore evident that the Sg. Semenyih water treatment plant will be considerably

water stressed in the medium term until 2014 with water demands in demand centres

served or to be served by this plant exceeding supply available as early as 2011

onwards. Hence, it is extremely vital that a new source be developed urgently to

provide strategic support in this area and therefore not only be confined to supporting

KLIA water demands.

The increase in demand for Sepang and Kuala Langat area up to year 2014 is

estimated to be in the range of 100 Mld, half of that estimated for year 2010 to year

2020. A new source capable to cater for this increased demand will also enable the

Sg Semenyih plant to be relieved of supply to Salak Tinggi. In so doing, the Sg

Semenyih water treatment plant will have additional water that will prove valuable in

ensuring reliable supply for critical demand centres such as Putrajaya and Cyberjaya.

3.0 Alternative Supply Options

A feasibility study for the KLIA’s alternative water supply scheme was conducted in

May 2009. A total of ten alternative schemes are considered in the feasibility study

and the findings are summarized as below:

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Options Studied Remarks

1. Interlinking of existing mains and reservoirs from Semenyih System

Semenyih WTP already at maximum capacity. Pipeline along same corridor can be severed in the event of another landslide along pipe corridor. Very long pipeline needed plus land acquisition if new pipeline laid from balancing reservoir.

2. Supply from Langat System WTP already on overload and supply areas have to be augmented from Sg. Selangor System

3. Supply from Sg. Selangor System

Requires a Booster Pumping Station and 55km of pipeline and supply is reaching full capacity soon.

4. Ground water Based on JICA study, yield about 45 Mld for Kuala Langat. Bulk of it taken by Megasteel. Very limited potential. Proposed additional supply by Megasteel for expansion is from Sg. Langat with mining pond. Further investigation will take sometime and may come to same conclusion as JICA Study

5. New WTP at Paya Indah Wetlands

Potential for upto 300 Mld. Potential strong objection from NGOs and surrounding properties if ground water table is lowered too much.

6. New WTP and Supply from Putrajaya Lake

Potential for 50 Mld yield from 34km2 catchment. Will likely face objection from Putrajaya Corporation.

7. Direct Pumping from Sg. Langat

Water highly polluted. Have shutdown in the past due to high ammonia. LUAS may impose 10% average daily flow (ADF) as compensation slow downstream. Yield will not be adequate for this scenario.

8. Supply from Negeri Sembilan

Negeri Sembilan facing water shortage in that area. No potential.

9. Supply from Bernam Scheme

Require a dam, diversion canal and approximate 100km of pipeline. Potential yield of 868 Mld. This scheme is too far and too big to be considered a practical option to be implemented in 2 years with interstate agreement on tariff and other issues to be sorted out.

10. Supply from Sg. Labu with off-river storage

ADF ≈ 400-500 Mld depending on position of intake. Dry weather flow cannot sustain existing Salak Tinggi intake. Storage needed for regulation. Potential yield upto 105 Mld.

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4.0 The Proposed Scheme

Each of the alternative supply options were analysed thoroughly with regard to

several key factors such as quantum of supply, time required for implementation,

costs (in particular economy of scale) and environmental impact. Sg. Labu Off-river

Storage Scheme is recommended as the best alternative source of supply for KLIA

due to its vicinity, yield potential and economical cost.

The yield potential of 105 Mld is sufficient to cater for the demand increase of about

100 Mld in Sepang and Kuala Langat Districts up to year 2014 before the proposed

Langat 2 WTP is operational as described in Section 2.0 above.

The existing Salak Tinggi WTP draws its supply from Sungai Labu and has a design

capacity of 10.1 Mld. It is possible to consider increased abstractions from this river

but an off river storage will be required to improve the reliability and quantum of water

that can be made available for KLIA and its surrounding area.

The location plan of the scheme is shown in Figure 1.

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Figure 1: Location Plan of Sungai Labu ORS Scheme

In general, the proposed scheme will comprise of the following component of works:-

i) A river gate across Sungai Labu to maintain a minimum submergence required

for the abstraction at the intake.

ii) An intake structure and a 140 Mld capacity raw water pumping station to

transfer the raw water to the off-river storage reservoir.

iii) Approximately 1.2km of 1200mm diameter mild steel pipe to convey the raw

water from intake to the off-river storage reservoir.

iv) A 37m high and 800m long center claycore earthfilled dam and three (3)

numbers of saddle dam to obtain the required 9 MCM active storage. The

impounding reservoir will secure a realiable yield of 105 Mld for the treatment

plant.

ORS SITE LOCATION

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v) A 105 Mld capacity treatment plant to be implemented in a separate contract

by Pengurusan Asset Air Berhad (PAAB).

The general layout of the Scheme is shown in Figure 2.

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Figure 3: Aerial View of Intake Works and ORS During Construction

4.1 Design Concept

The total catchment area at the proposed intake is about 185 km2 with Sungai

Chinchang catchment contributing 85 km2. The average daily flow (ADF) in Sungai

Labu at the proposed intake is approximately 406 million liters per day (Mld).

However, its dry weather flow cannot sustain the existing Salak Tinggi intake of 10.9

Mld eventhough the flow is estimated at 40-50 Mld due to the lack of weir across the

river and also to allow for compensation flow past the intake. Therefore, storage is

needed for regulation.

A spreadsheet simulation model for water accounting was prepared to validate

different intake and storage pond sizes and to obtain the reliable yield and intake

pump capacity. Basically, the simulation is a water balance computation. A

compensation flow amounting to 38.4 Mld (10% of the ADF) was allowed in the

simulation i.e. there is no abstraction from the river when flows drop below 40 Mld. In

addition, because monthly data are used, it is assumed that abstraction is only 90%

of available flow. A further 5% is allowed for treatment plant loss. Based on the

simulation result, the estimated yield for a 9 million cubic meter (MCM) storage is

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approximately 105 Mld. The live storage of 9 MCM is about the maximum possible

from the proposed site. The yield storage curve is shown in Figure 4.

Figure 4: Yield-Storage Curve

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The intake is proposed at about 1.6 km downstream of the confluence between

Sungai Labu and Sungai Chinchang as shown in Figure 2. A river gate will be built

across Sungai Labu further downstream of the intake to maintain the water level for

raw water abstraction. Raw water will be pumped directly into the off-river storage

reservoir through a 1200mm diameter (dia.) mild steel (MS) pipe.

The intake and raw water pumping station is size to a capacity of 140 Mld, which is

33% bigger than the design capacity of the treatment plant. The intake plant is

capable to run overload up to 175 Mld if necessary. The bigger intake capacity will

allow higher pumping during the wet months to take advantage of the higher flow and

storm water available in the river. This is needed because in the dry season, flow in

Sungai Labu will not be sufficient for abstraction.

The live storage capacity of the ORS of 9 MCM is about 86 days storage for a 105

Mld treatment plant. The off-river storage is also required in order to cope with

potential pollution ‘spells’, during which the abstraction from Sungai Labu will have to

cease.

With the ORS incorporated into this scheme, it is evident that the proposed storage is

more than adequate to support the proposed abstraction of 105 Mld with water levels

being drawn down to its lowest equivalent capacity of 0.5 MCM only once over the

entire 50 year simulation period. This drawdown is a result of the extreme drought in

1975 that has been incorporated into the analysis.

The ORS also enable the scheme to cope with the pollution episodes at Sungai

Labu, as the longest spell of pollution experienced to date is about 40 days and the

storage in the ORS of 9 MCM is about 86 days storage which is more than sufficient

to enable the WTP to produce 105 Mld continuously without abstraction of water from

the river.

The ORS dam site has been identified near the confluence of Sungai Chinchang and

Sungai Labu. The proposed embankment dam is approximately 37m high and

approximately 800m long. The impounding area is around 0.5 square kilometers or

50 hectares, most of which are oil palm plantation and secondary jungle. The project

site topography indicates that three (3) numbers of saddle dams are required

southwards of the main dam, as shown in Figure 2. The total embankment fill

volume is about 2.0 MCM. The earthfill material will be sourced from within the

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reservoir by cutting the reservoir perimeter slope to 1 in 3 below the full supply level

of 45m.

5.0 Environmental Impact and Land Acquisition

Based on an impounded area of only 50 Ha of private land involving mainly oil palm

cultivation and some secondary jungle and no settlements, the project do not require

an EIA study. Based on the Department of Environment’s requirements only project

with impoundment of more than 200 Ha requires and EIA study. Even though EIA

study is not required a brief assessment of environmental impact was incorporated in

the Environmental Management Plan.

The findings of field survey showed that none of the flora and fauna encountered

within the project site are rare, threatened or endemic.

There are no settlements within the project site and hence no resettlement issues

arise from the project. The proposed limit of land acquisition has been submitted to

the State Land Office to initiate the land acquisition process; this will ensure that

construction works can proceed as planned. As shown in the table below about 84.2

hectare of land areas were acquired from private owners for the construction of the

Project.

Sungai Labu ORS Scheme

Private Land

(ha) State Land (ha)

No. of Lots Landuse

Raw Water Intake and Pumping Station

- 3.149 - Oil palm plantation, small fruit orchard and dog training centre

Off-River Storage Reservoir

84.229 - 26 Oil palm plantation and fruit orchard

5.1 Intake Works

5.1.1 General

The Intake Works for the KLIA Water Supply Scheme consists of a river gate, a river

intake chamber, 2 nos. 1.05m dia. pipeline, a 140 million litres per day (Mld) raw

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water intake pumping station, and buildings such as TNB Sub-Station and Consumer

Swithroom, Switch House, Staff Quarters, Transformer Yard and Guard House.

The proposed Intake Works are located approximately 11.3 km upstream of Sungai

Labu’s confluence with Sungai Langat. The site commands a catchment area of

approximately 185 km2, and is located 1.6 km downstream of Sungai Labu’s

confluence with Sungai Chinchang. Please refer to Figure 5 for the Intake Works

layout.

Figure 5: Layout Plan of Intake Works

Rivergate

PumpingStation

Staff Quarters

Switch House

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Figure 6: Aerial Photograph of the Intake Works

5.1.2 River Gate

A river gate will be built across Sungai Labu further downstream o

maintain the water level for raw water abstraction. The proposed rive

of a 4 bay 4.6m width x 1.5m high and a 1 bay 1m width x 1.5m high

structure. The river gate will be a reinforced concrete structure and co

central section of Sungai Labu. The proposed river gate is shown in Fi

Figure 7: Photo of the proposed River Gate Structure (Looking Upstream)

PumpinStation

Switch House

Staff Quarters

Rivergate

g

f the intake to

r gate consists

opening gated

nstructed in the

gure 7.

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The design of the river gate will ensure that sufficient environmental flow will be

released through the gate during drought to ensure the sustainability of the

ecosystems downstream of the proposed river gate. From the hydrological

assessment done, the environmental flow was estimated at approximately 38.4 Mld

(0.44 m3/s).

The river gate will be operated under 2 operational modes as follows:

Mode 1: Normal/Flood Operation

When water levels upstream of the river gate is above RL 6.7m, all gates are

opened. Water levels in river is favourable for abstraction.

Mode 2: Drought Operation

When water levels upstream of the river gate is below RL 6.7m, all gates are closed

except for the small gate (1m x 1.5m) to allow compensation release. Water will back

up water levels to a maximum of RL 6.7m upstream of gate to allow abstraction.

5.1.3 Raw Water Intake Pumping Station

The proposed raw water intake and pumping station is located on the right bank of

Sungai Labu approximately 1.6 km downstream of the confluence of Sungai Labu

with Sungai Chincang. It consists of 2 horizontal inlet pipes of 1.05 m diameter

leading into the raw water pumping station grit chamber. The raw water pumping

station platform levels will follow the proposed Sungai Labu flood bund level as

recommended in the Sungai Langat IRBM Study to allow for future flood bund

connection. The proposed plan and sections of the raw water intake pumping station

is shown in Figure 8 and Figure 9.

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Figure 8: Plan of Intake Pumping Station

Figure 9: Cross Section of Intake Pumping Station

The deciding factors for abstraction are the water level in the river and its water

quality. When water levels are favourable, abstraction will commence, and this will

continue unless if the water quality in the river deteriorates. There are two (2) river

monitoring stations that will be established to detect pollution in the river. These

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stations will monitor and warn the operators if pollution levels in the river are beyond

the permitted levels.

The normal abstraction rate is 140 Mld. However, the abstraction can be increased to

a maximum of 175 Mld, if conditions are found to be favorable and if there is a need

for it. No abstraction will be done, if the flow in the river is less than the compensation

flow requirements. Raw water will be pumped directly into the ORS reservoir through

a 1200mm diameter (dia.) mild steel (MS) pipe. The 9 MCM active storage of the

ORS is meant as a buffer and will enable up to an approximately 3-month supply to

the proposed treatment works of 105 Mld capacity without replenishment, if

abstraction is not favorable in Sg. Labu. This ensures that the project is viable and

guarantees the supply to the KLIA reservoirs.

5.2 Off River Storage Reservoir

5.2.1 General

An off-river storage site has been identified approximately 1km south of the

proposed intake. The reservoir site is mainly occupied by oil palms and secondary

jungle. A 37m high, 800m length earthfill embankment dam will provide an active

storage of 9 million cubic meters (MCM) with a reservoir surface area of around 50

hectares. The storage capacity is about 86 days storage for a 105 Mld treatment

plant.

The project site topography indicates that three (3) numbers of saddle dams are

required southwards of the main dam, as shown in Figure 10. In order to maximize

the storage volume, the reservoir perimeter slope will be cut to 1 in 3 slope below full

supply level of 45m LSD.

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Figure 10: Off-River Storage Reservoir

Figure 11: Aerial Photo of ORS

The elevation/area/storage curves have been derived from

the impounding reservoir with 2.0 m contour intervals. T

Figure 12.

Main Dam

Saddle Dam C Saddle Dam B

Spillway

DrawoffTower

Main Dam

SaddleSaddle Dam C

detailed ground survey of

he curves are shown on

Saddle Dam A

Dam B

Saddle Dam A

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Figure 12: Elevation-Area-Storage Curve

From the yield analysis for a 105 Mld scheme, the minimum active storage required

is 9 MCM, and the corresponding full supply level (FSL) is 45.0 m LSD. Hence, the

gross storage of the reservoir is about 10.5 MCM, taking into account of its 1.5 MCM

dead storage.

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The key features of the ORS are as tabulated below:

Impounded area 0.5 km2

Live storage 9.0 MCM

Dam crest level 47.0m LSD

Top of wave wall / parapet wall level 47.5m LSD

Dam crest width 10m

Dam crest length 800m

Dam height 37.0m

Full supply level 45.0m LSD

Maximum flood level ( during PMF )

45.8m LSD

Drawoff tower operating deck level 47.0 LSD

Spillway / drawoff culvert 2.0m x 2.0m square

Spillway type Drop Inlet

Spillway crest level 45.0m LSD

Spillway diameter 2.0m

Spillway weir length 4.0m

PMF Discharge 6.15 m3/s

Stilling basin size 10.0m x 2.0m

Saddle dam 3 nos.

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5.2.2 Dam and Appurtenant Structures

The orientation of dam axis has been selected based on the following consideration:

shortest crest length, minimum fill volume and at the same time maximize the storage

volume.

The selected dam axis follows the orientation of the left and right abutment ridges

which rises gently beyond the embankment crest level of 47m LSD. The dam is

designed as an earthfilled claycore embankment. Figure 13 shows a typical dam

section. The chosen dam axis resulted in a layout with a crest length of 753 m and a

height of 37 m. The approximate total fill volume is about 2 million cu.m.

There are three (3) numbers of saddle dams located southward of the main dam

namely Saddle Dam A, Saddle Dam B and Saddle Dam C. All the saddle dams and

main dam can be accessed by the access road running along the east side of the

reservoir rim. The reservoir formed by the dam would inundate an area of 50 ha.

Figure 13: Dam Embankment Cross-Section

A drop-shaft spillway is provided to pass safely the Probable Maximum Flood at the

main dam. The routed flood will be discharged through a 2m x 2m square culvert,

which is also used for diversion of construction flood. The spillway general

arrangement is shown in Figure 14 and Figure 15.

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Figure 14: Spillway

Figure 15: Photo of Spillway and Main Dam

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The outlet works comprise a wet well Drawoff Tower and a single line outlet pipe at

Saddle Dam B. For selective drawoff of the more oxygenated water at the top, the

drawoff tower will have five inlet levels with isolating stainless steel penstocks. The

inlets are at level 40m, 35m, 30m, 25m and 20m LSD. The general arrangement of

the tower is shown in Figure 16.

Figure 16: Drawoff Tower

Figure 17: Photo of Drawoff Tower and Saddle Dam B

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Impounded reservoirs are known to experience thermal stratification due to

temperature distribution with depths. An effective way to alleviate the stratification

problems is to mix the water in the reservoir to bring the deoxygenated layer to the

surface. A perforated pipe compressed air system has been incorporated. Compress

air will be pumped to the bottom of the reservoir through a perforated HDPE pipe.

The air bubbles released though the perforated pipe will create a turning effect on the

reservoir body to mix the water between the upper and lower layer. This in turn will

improve the reservoir water quality by increasing the dissolve oxygen content and

stabilises the ecosystem and prevents excessive blooms of algae and zooplankton.

5.3 Earthquakes Impact

The off river storage site lies within the western portion of the seismically stable

Sunda Shelf which also comprises of Southern Thailand, East Malaysia, Kalimantan,

Indo-China and South China Sea. However there are a number of small seismic

events that have been recorded near the Sunda Shelf. The epicentres of these

earthquakes lie in Sumatra and almost all are located less than 100 km depth.

The Contact Zone between the Indian Plate and the Asian Plate is where maximum

seismicity is concentrated and where earthquake of magnitude beyond 6.5 are

located. The boundary of this zone is approximately 200 km from the off river

storage dam site.

Between Nov 2007 to May 2008, reactivation of Bukit Tinggi faults has cause a

series of cluster earthquakes which had magnitudes between 1.8 – 3.5 with the focal

depth less than 10km. Although these events are the first natural earthquakes with

epicentres on Peninsular Malaysia, the magnitude is too negligible to cause any

effect to the existing structures.

The design of the embankment has taken seismic effect into consideration by

incorporating ground acceleration in the stability analysis. Although the estimated

acceleration of the 26th December 2004 earthquake in Sumatra is only 0.55g, it is

more appropriate to use 0.1g since this event may occur at any area where the

epicentre could be nearer to the off river storage dam site. The U.S. Corps of

Engineers has also adopted 0.1g seismic coefficient for seismically stable areas. The

stability analysis shows a factor of safety of 1.25 which is above the required of 1.0.

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5.4 Reservoir Operating Rule Curve

The control rule curves are used to aid in the day-to-day reservoir operation by

specifying the minimum desirable storage level to be maintained as closely as

possible during the different times of the year while at the same time, providing

adequate raw water supply to satisfy various demands.

The curves are generally derived by carrying out operational studies using historical

hydrometric records, i.e. mainly long-term streamflow records. In addition it is also to

be reviewed from time to time based on the experiences gained in operating the

reservoir.

Seven (7) runs based on the net yield of the pump storage system operation were

carried out. They range from 60 Mld to 105 Mld, i.e. the highest yield associated with

the maximum storage capacity of 9.0 MCM. The results are shown in Figure 18.

The rules curve allows abstraction of more than 105 Mld, i.e. above the design net

yield if the live reservoir storage at any month is above the specific curve in the rule

curve diagram but subject to other constraints such as the hydraulic capacity of the

WTP and the offtake. Conversely, if the rule curve fells below the targeted level, then

abstraction should be curtailed accordingly to a lower abstraction rate.

The derived rule curves for Sg. Labu pump storage reservoir system should be

reviewed regularly so as to permit the incorporation of acquired experiences through

actual operation of the reservoir system. To do so, this essentially entails keeping

meticulously pertinent hydrometric (rainfall and evaporation rate) and operational

records, such as accurately accounting for abstraction and flow past the intake to

obtain the natural river flow data.

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0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

8.0

9.0

10.0

JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC

Month

MCM

105 Mld 95 Mld 90 Mld 90 Mld

80 Mld 70 Mld 60 Mld FSL

Figure 18: Operating Rule Curve

6.0 Raw Water Quality

Assessment of the raw water quality at the proposed intake was previously carried

out during the Engineering Feasibility Study stage using raw water quality information

from 2007-2008, which was obtained from Puncak Niaga (M) Sdn. Bhd. (PNSB), as

well as one grab sampling carried out by the Consultant in May 2009.

Based on the earlier assessment, the parameters of the raw water was found to be

within the acceptable range of the Ministry of Health (MOH) Raw Water Guidelines,

except for certain months which shows high peaks for parameters such as colour,

COD, ammonia, iron and manganese.

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Although the water quality data seemed to indicate that the quality of the raw water is

acceptable for use as a potable supply based on information from PNSB, there have

been many incidences when the Salak Tinggi plant has been shutdown due to

pollution episodes at Sungai Labu. The incidences occur mainly during periods of low

flow when the dilution capabilities of the river are at its lowest. The types of pollutants

observed by the plant operators are generally similar on all occasions (high

ammonia, chemical odour, foamy substances, blackish coloured waters).

It is therefore, strongly suggested that enforcement by the authorities be carried out

more diligently. During each event when pollution is detected at the Salak Tinggi

plant especially for long periods, it should be possible to track down the sources of

pollution and impose heavy penalties and stern actions on these premises. Only in

this way, can the sustainability of new and existing intakes within Sungai Labu be

ensured. If enforcement is not strictly carried out, the situation will worsen especially

since there are large industrial areas upstream and this will jeopardize the water

resources availability.

In view of the occasional pollution issues, the proposed KLIA alternative water supply

scheme has allowed for stoppage of pumping of the raw water during these

incidences. A monitoring station is provided about 0.6 km upstream of the intake site

to alert the operators to stop pumping when pollution is detected.

7.0 Plant Operation and Challenges

During commissioning of the plant, the contractor encountered a few challenges that

prevented them from carrying out the 7 days testing and commissioning as planned.

The challenges are namely the low quantum of flow the river and the quality of the

raw water.

7.1 Low Flow

Plant commissioning was carried out in the month of July where historical data show

it is the driest period of the year in west coast peninsular Malaysia. The flow in the

river during this period is only averagely about 100 Mld to 150 Mld. Subtracting 38

Mld for compensation flow and 10 Mld for the existing Salak Tinggi Intake (STI)

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downstream, the plant should still be able to abstract about 50 Mld to 100 mld into

the ORS. However this was not possible due to the low efficiency of the existing STI

downstream. The existing STI eventhough only of 10 Mld capacity needed the

proposed river gate to release a flow of about 100 Mld in order to achieve the

required river level to flow into the intake as it does not have a river gate itself.

To overcome this setback, the contractor together with the STI plant operator have

stacked sand bags across the river at the existing STI to channel the required river

flow into the intake. After this counter-measure was carried out, the Sungai Labu

Intake has since abstracting averagely 75 to 105 mld daily and 175 mld during rainy

days.

Even though the intake is designed to have a maximum plant capacity of 175 mld, 6

numbers of smaller capacity pumps of 35 mld each are installed. This is so that the

plant will be able to operate even during low flow as the smaller pump capacity will

be able to abstract even the lower flow instead of letting it to waste. During high flow

the plant can run at a capacity of 175 mld with 5 pumps running and 1 pump standby.

7.2 Poor Water Quality

The poor raw water quality in the river is partly attributed by the dry weather. As the

flow reduces; the concentration of pollutant increases and jeopardizing the water

quality. The pollutant encounter during commissioning of the plant are similar to

those describe in Section 5. From the river water quality monitoring exercise carried

out during the construction period, the JPS Drain located just upstream of the river

gate had been notice to consistently discharging high ammonia content flow in the

range of 4 mg/l to 6 mg/l into the Sungai Labu. To prevent abstracting this heavily

polluted water into the ORS a 1.0 meter diameter diversion reinforced concrete

culvert was constructed to divert the flow from the JPS drain downstream of the river

gate. With the JPS drain diverted, the ammonia content in Sungai Labu reduces to

about of 0 mg/l to 3 mg/l but still occasionally fluctuate to as high as 6 mg/l, where the

intake was forced to stop operation for about 3 days. This is likely due to discharge

from sewerage treatment plants and industrial area upstream.

The water quality in the ORS is also monitored regularly. The ammonia content is

averagely 1.0 mg/l which is below the Ministry of Health (MOH) guideline of 1.5 mg/l.

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The raw water quality is also likely to be improved after being aerated as the water

cascades down the outfall channel. The water quality in the ORS can be improved

further by operating the destratification system to mix the water in the reservoir and

bring the deoxygenated layer to the surface for aeration to increase the dissolved

oxygen content in the water to a favourable level. A vertical water quality profiler was

installed on the ORS to monitor the real-time water quality of the reservoir from the

surface to the bottom of the lake. This will give an indication when to operate the

destratification system, i.e. when the water quality of the bottom layer and the top

layer differ greatly.

8.0 Impact of Project

With the implementation the proposed Sungai Labu Off-River Storage Scheme,

KLIA’s current and long term water demands are secured and at the same time it

provides valuable supply to partially offset water shortages in the State by serving

other demand centres in Sepang and Kuala Langat simultaneously. This supply is

strategically located and will provide extremely valuable support by relieving the

existing Sg. Semenyih WTP of supply to KLIA and surrounding areas thus enabling

this plant to be in a position to provide more reliable supply for other important

demand centres such as Putrajaya and Cyberjaya.

This project being implemented under the “Projek Ransangan Ekonomi 2” (PRE2)

Scheme is anticipated to stimulate the economy of the country during this global

recession as most materials and equipments for the project are sourced locally. It

also creates further job opportunities for the construction industry.

For more information about the project and for permission to use material from this paper can submit request to http://www.jba.gov.my. ALL RIGHTS RESERVED. No part of this work covered by the copyright hereon may be reproduced or used in any form without the written permission of the authors