River Engineering and Urban Drainage Research Centre (REDAC), Universiti Sains Malaysia has been appointed to provide consultancy services for the drainage works as part of Civil and Structure components for the proposed “Cadangan Mendirikan Sebuah Klinik Kesihatan Taiping – 2 Tingkat (Jenis KK2) Di Atas Lot 2089, Jalan Tupai, Mukim Tupai, Daerah Larut & Matang, Perak Darul Ridzuan”. In this project the Government is planning to construct a drainage system to comply with the new guidelines of Department of Irrigation and Drainage (DID), Urban Stormwater Management Manual for Malaysia (MSMA).
The Government of Malaysia via Public Works Department (JKR) Malaysia has planned to construct a new building for the Taiping Town Clinic and its infrastructure on the area approximately 7 acres in Larut & Matang District in Perak. This project consists of the construction of a double storey building block, chemical store, condenser block, TNB block, store and garage, security guard house, sewerage treatment plant, pavilion and car park. The soil profile for overall project area is consistent from silty sand at the first 10m depth to hard layer of silty clay. Ground water level is observed at 0.95m to 1.35m depth from original ground surface.
Proposed Drainage System:
The proposed drainage system which is known as Bio-Ecological Drainage System (BIOECODS) is consistent with objectives of new stormwater management approach which focus on the control of both the quantity and quality of urban runoff. 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.
The new stormwater management approach, BIOECODS, based on set of broad and holistic principles for effective stormwater environment management:
- The establishment of a storage-oriented approach for controlling runoff quantity from development sites;
- The identification of the environmental values (or benefits uses) of particular water bodies which are to be protected;
- The establishment of objectives which will achieve required levels of flood protection and water quality enhancement;
- The establishment of water quality management strategies;
- The development and implementation of monitoring and surveillance programs to ensure that runoff quantity and water quality (or environmental) objectives are being maintained; and
- The implementation of research programs to gain a better understanding of the behavior of aquatic systems in order to improve water quality design and management technique.
By integrating stormwater management planning with landscape and environmental planning, it will add aesthetic and recreational values to the water amenities. This site is planned to become a showpiece of the new drainage system for the Perak State and will also provide the database to support the new stormwater management manual as we still lack of data for local conditions and to evaluate the effectiveness of the stormwater runoff quantity and quality control system.
Proposed Drainage Layout:
The proposed drainage system has several runoff control facilities to regulate the runoff from the site as shown in Figure 1. The receiving waterway is made up of an upgraded covered concrete lined drains before discharging to River Batu Tugoh nearby.
The new environmental-friendly drainage system, BIOECODS, uses “control at source” principle simulating the natural hydrological cycle in urban areas by combining infiltration, detention storage, retarded flow as well as runoff treatment techniques. Among the stormwater facilities provided are grassed swale, underground detention storages and dry ponds. The design concept is given in Figure 2.
a) Grassed Swale (Figure 3)
Grassed swale is designed to cater any excess water from perimeter drain (for individual building) whilst the flow from pervious and impermeable surface will be directed to the grassed swale. The grassed swale is defined as grass earth channel combined with subsurface module which enclosed within a permeable geotextile. 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 stormwater. The vegetated systems remove pollutants by means of sedimentation, filtration, soil absorption and plant uptake.
b) Detention Storage (Figure 4)
The excess stormwater is stored in the subsurface detention storage. The storage modules have been designed to be places at the connecting points, junction and critical point of the system. These detention storages are provided to reduce flows from the building, regulating flow velocity which causes the gravity settling of particulates and increase the infiltration process where all these mechanisms will control the quality and quantity of stormwater runoff.
c) On-site Stormwater Detention (OSD)
The excess stormwater is also stored in the dry pond constructed with a storage function. The dry pond is a detention basin with the purpose to temporary store the stormwater runoff. This detention basin is design 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 dry pond system in less than 24 hours. Therefore, the quantity and quality of the runoff from developed areas can be maintained to be the same as pre-development condition. OSD is normally dry or empty when not in operation. It will be utilized for multi-purpose use to incorporate passive and active recreational areas such as public parks and open space or sporting facilities.
The proposed BIOECODS is an applicable concept that will fulfill new urban stormwater management objectives to restore each component of the hydrological cycle to its natural level. This new stormwater management approach has taken into broad consideration with the purposes:
- to provide safety for the public,
- to minimize and control nuisance flooding,
- to stabilize the landform and erosion control,
- to enhance the urban landscape, and
- to minimize the environmental impact of urban runoff on water quality.
REDAC would like to thank Public Works Department (JKR) for the opportunity to participate in this project.
Lai, S.H. & Mah, D.Y.S. (2012). Field Investigation of a Dry Detention Pond with Underground Detention Storage, Hydrological Sciences Journal, Vol. 57, Issue 6, pp. 1249-1255, DOI: 10.1080/02626667.2012.69201 <Website>