Slope alteration by cutting or filling embankments can trigger slope failures, especially in the event of a major rainfall and/or without applying proper slope protection measures and slope drainage. Unplanned or improper slope construction methods may cause slope failures or landslides to occur within the site or in neighbouring areas.
Target
Control of slope cutting activities to mitigate erosion and landslides.
Standard Operating Procedures
4.1 Refer to the EIA/PMM and AEC/MD for slope stabilisation measures. Check and identify:
i. Buffer requirements.
ii. The best engineering practices for slope stabilisation approved by relevant Local Authorities (examples shown in Plates 14 – 16).
iii. Location, method and sequence for implementing slope protection measures such as slope cutting sequence, runoff management and sediment control facilities i.e., cascade drain, toe drain, berm drain, etc.
4.2 Implement slope stabilisation measures as per the EIA/PMM and AEC/MD.
4.3 Minimise removal of existing vegetation to aid slope and soil zone stabilisation.
4.4 Commence slope cutting immediately after the area is cleared.
4.5 Conduct slope cutting in stages and in a controlled manner.
Plate 14: Example of soil nail wall for slope stabilisation.
Plate 15: Example of Nehemiah retaining wall for slope stabilisation.
Plate 16: Example of terracing and cover crops for slope stabilisation.
4.6 Apply rock dissipater at the end point or at the toe end of the incomplete adjoining permanent drainage lines constructed along sloping areas.
Plate 17: Example of rock dissipater at the end point of drainage.
Source: Guidelines on Land Disturbing Pollution Prevention and Mitigation Measures, 2017 (Appendix B)
4.7 No stockpiling materials on slopes, slope crests or any probable locations susceptible to landslides or endangerment of the public or adjacent properties.
4.8 Appoint a geotechnical engineer and professional geologist to jointly draw up the slope rehabilitation and stability monitoring plan (if such requirement is stated in the AEC/MD), even after the project has commenced. Refer to Appendix 2 for the general content of the slope rehabilitation and stability monitoring plan.
4.9 Submit slope rehabilitation and stability monitoring plan to JMG for approval.
4.10 Submit approved slope rehabilitation and stability monitoring plan to the EPD.
4.11 In addition, conduct the following steps for stabilised slopes.
i. Refer to the slope maintenance programme and slope maintenance manual prepared by the Submitting Engineer.
ii. Conduct visual inspection of all stabilisation structures. Record any defects in the stabilisation structures or any undeveloped slopes adjacent to the cut slope. These include special structures, such as drains, to ensure slopes are stable.
iii. Install instruments, such as inclinometers and ground/building settlement markers, to monitor slope movement, if specified in the slope maintenance programme.
iv. If there are signs of slope movement on RC stabilised structures, engage a geotechnical engineer and professional geologist to study the causes in detail, and take immediate action.