Earth control measures (ECM) are implemented in construction sites to prevent silt from polluting our waterways.
Construction activities inevitably involve land clearance, which leads to generation of bare surfaces i.e. exposure of soil to erosion. When it rains, silt washes down from the exposed earth surfaces.
Before starting any construction work, contractors are required to obtain the Clearance Certificate to commence works from Public Utilities Board (PUB) by submitting the ECM Plan, designed and endorsed by the Qualified Erosion Control Professional (QECP).
Contractors are then required to install the ECM on site according to the ECM Plan.
Furthermore, contractors shall ensure that the QECP conducts monthly site inspection to verify ECM implementation and its effectiveness during construction phase and submit a pictorial QECP inspection report according to LTA’s Requirements for QECP Inspection Report.
An effective ECM requires erosion control and sediment control with the primary focus on the earlier.
Erosion control measures aim to minimise the extent of soil loss and water pollution. Contractors need to follow these minimum requirements:
- Minimise formation of bare surfaces by retaining as much of the existing vegetation during site clearance.
- Pave bare surfaces and all construction access with concreting, milled waste or other suitable materials.
- Protect bare slopes with close turfing, concrete grouting, erosion control blanket or canvas sheet.
- Protect earth stockpiles with erosion control blanket or canvas sheet.
- Restore ground cover over disturbed areas that have become bare.
- Carry out trench excavation work in sequence with the progress of permanent works.
Sediment control measures aim to contain, store and treat the eroded soil from entering our waterways. Contractors are required to follow these minimum requirements:
- Construct concrete-lined cut-off drains along the perimeter of the construction sites.
- Erect silt fences in front and along the perimeter cut-off drain along the perimeter of the boundary of the site.
- Install intermediate silt traps along the perimeter cut-off drain.
- Install a treatment system equipped with a continuous turbidity and total suspended solids (TSS) monitoring device and CCTV before the discharge into public drain.
- Turbidity curtains must be installed for construction works near water bodies. The design, fabrication, and installation of the primary and secondary turbidity curtains must be conducted to ensure that the turbidity of water shall not exceed the pre-existing levels or 50mg/l.