Development activities lead to soil erosion, which degrades water quality by increasing turbidity levels and total suspended solids. Temporary drainage systems as well as erosion and sediment control structures shall be provided to control and provide effective retention and discharge of sediment runoff.
Target
Protection of water quality by minimising erosion and sedimentation impact.
Standard Operating Procedures
2.1 LAND
2.1.1 Refer to the EIA/PMM, AEC/MD and latest mitigation measures map approved by the EPD. Check and identify:
i. Runoff management and sediment control facilities i.e., temporary earth drains, check dams, silt fences, silt traps and sediment basins etc., to be provided at the site.
ii. Specifications, locations and sequences in the provision of runoff management and sediment control facilities.
2.1.2 Construct runoff management and sediment control facilities at the site prior to carrying out earthwork activities. Below are general sequences for providing the facilities.
i. Mark site and/or buffer boundaries based on SOPs detailed in Environmental Condition: Control of Site Development.
ii. Construct temporary perimeter earth drains and sediment basins prior to carrying out earthwork activities. Refer to Figure 5.
iii. Connect temporary earth drains to the sediment basin to divert all surface runoff into it.
Figure 5: Illustration of earthwork activity by stages.
Figure 6: Typical design of a Sediment Basin (1).
Source: Urban Stormwater Management Manual for Malaysia, 2nd Edition, DID 2012.
Figure 7: Typical design of a Sediment Basin (2).
Source: Urban Stormwater Management Manual for Malaysia, 2nd Edition, DID 2012.
Figure 8: Typical design of a Silt Trap.
2.1.4 No construction of runoff management and sediment control facilities in rivers or watercourses.
2.1.5 Conduct site clearing at the targeted phase of the development site based on the development schedule.
2.1.6 Conduct earthwork activities in stages at the targeted phase of the development site and avoid conducting activities during rainy days.
2.1.7 Compact exposed surfaces i.e., backfill areas, construct slope embankments, road base, etc., to reduce soil erosion.
2.1.8 Conduct maintenance (sediment removal or desiltation by excavation) on sediment control facilities i.e., temporary earth drains, check dam, and sediment basin, periodically with increasing frequency after each rain event.
2.1.9 Start applying temporary soil stabilisation methods to exposed areas after reaching final formation level on any portion of the site. Install plastic sheet covers or geotextile mats as temporary soil stabilisation measures.
Plate 7: Example of plastic sheet cover.
Plate 8: Example of geotextile mat.
Source: Urban Stormwater Management Manual for Malaysia, 2nd Edition, DID 2012.
2.1.10 Plant cover crops on exposed surfaces e.g., Mucuna bracteata, Brachiaria ruziziensis, etc. to reduce soil erosion.
Plate 9: Example of geotextile mat.
Source: Urban Stormwater Management Manual for Malaysia, 2nd Edition, DID 2012.
2.1.11 Refer to SOPs contained in Environmental Condition: Slope Stabilisation if cover crops are not suitable due to slope surface type, such as rocky slopes.
2.1.12 Place any earth materials stockpile (either imported from borrow pit or excavated at the site) at a minimum distance of 30 metres from any watercourse to avoid potential soil migration or the distance specified in the AEC / MD.
2.1.13 Provide temporary perimeter controls at the earth materials stockpile, such as berms, and cover the materials with canvas sheets.
Plate 10: Example of loose earth materials covered with canvas sheets.
Source: Guidelines on Land Disturbing Pollution Prevention and Mitigation Measures, 2017
2.1.14 No disposal of earth, biomass waste, sediment, solid waste, sewage or scheduled waste into the drainage, river or waterway.
2.1.15 Refer to the Malaysian Standard listed in Appendix 1 for additional reference on erosion and sediment control system.
2.2 SEA
2.2.1 Install/construct sediment plume control systems, such as silt curtains and/or embankments, prior to reclamation/ dredging/excavation and cofferdam construction activities.
2.2.2 For Projects involving the construction of a cofferdam, install sheet piles for the construction of the cofferdam before commencing reclamation work.
2.2.3 Perform visual inspections regularly to determine whether maintenance is required. The following are recommendations for inspection and maintenance activities:
i. Check whether the silt curtain is twisted.
ii. Replace worn or broken anchor lines.
iii. Remove any solid waste/dirt caught on the silt curtain.
iv. Check for any signs of bund breaching
Plate 11: Maintenance of installed silt curtain.