INGENIEUR
Figure 10: Cross Section A-A Through Left Abutment
Figure 11: Existence of jointed
and sheared zone in the rock
mass facing at Weng Lee
Quarry
capacity of the rivers. Alternative
source of filter materials using
crushed rocks was investigated.
Large quantities of granite
boulders were available at
the dam site. The contractor
eventually invested in rock
crushing machines and set
up a filter processing plant as
shown in Figure 12. A laboratory
test (non-erosion test shown in
Figure 13) was set up for testing
the acceptability of the crushed
rocks filters.
Potential Risk to Existing
Dam
Figure 12: Rock Crushing
Machine and Filter
Figure 13: Non –Erosion Filter
Test Processing Plant
6
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VOL
- MARCH 2016
VOL65
55JANUARY
JUNE 2013
Construction of the new dam
and raising the height of the
existing dam involved foundation
excavation adjacent the existing
dam and at the downstream toe
of the existing dam. Due to the
reservoir water level at EL43.00
m, high water pressure gradient
exiting cut slope for foundation
excavation posed risk to the
safety of existing dam.
To mitigate the risk, it was
necessary to lower the reservoir
water level of Mengkuang
Dam from elevation EL43m to
EL34m.
The original contract was
based on the premise that the
existing reservoir storage water
must be maintained at full
supply level of EL43m to secure
water supply from the dam to
Sg Dua Water Treatment Plant
(WTP). The State Government
of Pulau Pinang was concerned
that reducing the storage water
will affect security of the water
supply system. An alternative
water source as backup at
time of water shortage was
necessary. KeTTHA sought
the agreement from Lembaga
Sumber Air Negeri Kedah
(LSANK) to release water from
Beris Dam for supply to the
Sg Dua WTP in time of need.
With the co-operation of the
State Government of Kedah,
Pulau Pinang and Federal
Government, the issue was
resolved. The reservoir water
level of the existing dam was
lowered in July 2014 to facilitate
the construction of the dam
expansion project.