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.

Figure 1 Perimeter Swale		Figure 2 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.

Figure 3 On-Site Detention Basin (Dry Pond)

Figure 4 Subsurface Detention Storage

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.

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.