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INTRODUCTION
The Public Works Department (JKR) has
constructed a new building for the forensic wad at Hospital Bahagia Ulu
Kinta, Tanjung Rambutan, Ipoh, Perak Darul Ridzuan. In this project, the
drainage system has been designed to comply with the new guideline which is
published by Department of Irrigation and Drainage (DID) in the year 2000
and gazetted by the government in the following year, namely Urban
Stormwater Management Manual for Malaysia or MSMA. River Engineering and
Urban Drainage Research Centre (REDAC), Universiti Sains Malaysia has
assisted JKR in-house design team extensively during design stage. Alira
Sepakat Sdn. Bhd. was appointed by the main contractor as the nominated
specialist sub-contractor in realizing this project.
PROJECT BACKGROUND
This project consists of
the construction of a single building, which includes administration unit,
clinical unit, forensic block and wad. The project covers a catchment area
of 1.51 hectares. More than 60 % of the total area has been developed into
impervious area such as paved road and car park, sheltered walkway, and
utilities other than the building. The land use changes from undeveloped to
developed areas have caused approximately 50% increment of peak flow
discharge from 0.36m3/s to 0.55m3/s on receiving water
body.
DESIGN CRITERIA
The design criteria for
this project were based on MSMA. The manual recommends “control-at-source”
concept in order to manage this valuable water resources as an asset towards
creating a sustainable environment. The objectives of new stormwater
management approach emphasize the control of both the quantity and quality
of urban runoff.
DRAINAGE SYSTEM
The proposed drainage system is known as
Bio-Ecological Drainage System (BIOECODS). This has been embodied in the
concept of ecologically sustainable development which is aimed at ensuring
that development can occur without long-term degradation of natural
resources and the environment.
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Figure 1
Perimeter Swale |
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Figure 3
Ecological Swale |
Grassed swale (Figures 1 and 2) was designed
as a conveyance to serve the post-development runoff generated from the
developed catchment area.
The grassed swale is defined as grass earth channel combined
with subsurface modules which enclosed within a permeable geotextile. The
grassed swale acts as main conveyor on collecting and discharging runoff
while the subsurface module acts as water quality treatment facility and
assist in dewatering the base of grassed swale. The grassed swale is
designed by taken into consideration of peak flow attenuation, soil erosion
and safety to the public. Grassed swale has the ability to reduce on-site
peak flow rates by increasing the roughness of the channel and infiltration
rates. These vegetated systems also provide runoff quality treatment by
removing low concentrations and quantities of TSS, heavy metals,
hydrocarbons and nutrients from storm water. The vegetated systems remove
pollutants by means of sedimentation, filtration, soil absorption and plant
uptake.
On-site detention pond
facility was selected as storm water quantity control facilities for this
project. On-site detention pond was designed to regulate the outflow
discharge to pre-development discharge limit (Figure 3).This detention basin
is designed to store to the surface of 600mm of the excess rainfall under
design average recurrent interval of 10-year and blend with the surrounding
landscape. The outflow path is controlled by orifices in order to drain the
pond system in less than 24 hours. The excess storm water is also stored in
the subsurface detention storage as illustrated in Figure 4. The storage
modules have been placed at the connecting points, junction and critical
point of the system. The detention storage are provided to reduce flows from
the building, regulating flow velocity which cause the gravity settling of
particulates and increase the infiltration process where all these
mechanisms will control the quality and quantity of storm water runoff.
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Figure 3 On-Site
Detention Basin (Dry Pond) |
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Figure 4 Subsurface
Detention Storage |
CONCLUSIONS
This project has applied new storm water
management approach to minimize the impact of urbanization on the
environment. It adopts an integrated approach to obtain both practical and
cost effective solutions for drainage system. With this drainage system, the
quantity and quality of the runoff from new developed areas at Hospital
Bahagia Ulu Kinta can be maintained to be the same as pre-development
condition.
ACKNOWLEDGEMENT
REDAC would like to thank
Public Works Department (JKR) for the opportunity to participate in this
project.
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