We care for our environment
Protecting and enhancing the environment is an increasingly important role for all of us. The environment is one of the three key pillars of sustainability, alongside society and economic performance.
E22 is the only expressway in Malaysia which provides mitigation measure to eliminate potential adverse impacts to the water quality in the event of a spillage of dangerous and hazardous chemicals from heavy transport vehicle travelling on the expressway.
E22 crosses Sg. Layang Reservoir from KM33 to KM37 which is an environmentally sensitive water catchment area and also the main source of water supply for Johor Bahru District.
Pollutant Removal System (PRS) were introduced as the mitigation system which is specifically planned and designed to intercept and remove chemicals or pollutants from the surface run-off and preventing them from reaching the Sg. Layang Reservoir.
The process for the Pollutant Removal System is illustrated in a schematic diagram as shown below:
The design is based on the Manual Saliran Mesra Alam Malaysia (MSMAM) and the US Department of Transportation, Federal Highway Administration (June 1996).
Stage 1: Grassed Swale
The first line of defence consists of grassed swale and was designed primarily to trap pollutant from the surface runoff. The primary pollutant removal mechanism involves allowing sufficient time and slow flow velocity for heavier particles, oil and grease to be trapped by filtration and infiltration. To enhance the efficiency of infiltration and trapping of pollutants, sub-soil perforated pipes are installed at below the bed of the swale.
Stage 2 : Gross Pollutant Trap (GPT)
It is common that during rainy event debris may be washed down from the upstream and enters into the pollutant removal system. It is therefore recommended to include a GPT to screen out the larger debris. This is necessary considered the protection that will be required for the downstream mechanical pollutant removal unit. An emergency spillway is incorporated in the design to provide in the event that screen is blocked by debris.
Stage 3 : Oil/Grease Trap and Chemical Filtration
The main function to this unit is to separate oil and grease and remove chemical spillage to achieve Standard ‘A’ water quality (Department of Environment) in the receiving waters.
The basic feature consists of containment of oil and grease in compartments to allow removal physically (pumping) from the unit and filtering of chemical spillage by sand and activated carbon.
Stage 4: Retention
The retention unit assumes the function of an infiltration basin that treats surface run-off through absorption and filtration. By incorporating specific plants, trees and shrubs, the retention unit mimicks the ecosystem of an upland forest floor.