2. /
  3. Site Preparation
  4. /
  5. Mechanical (Excavator/Barge)
  6. /
  7. Site Preparation: Mechanical – 4.0 Surface Runoff

CONTROL OF surface runoff

 

Any bare area within the processing site and temporary occupation sites such as workers quarters and site office is prone to detachment of soil and associated with weathering agents i.e. rain and wind may aggravate the impacts of soil erosion. Detached soil is carried by surface runoff and deteriorates the nearest receiving waterbodies i.e. any established drainage system at the temporary occupation site and river by increasing turbidity levels and total suspended solids. The temporary drainage system and erosion and sediment control structures should be provided to control and facilitate effective retention and discharge of sediment runoff.

Target:

Protection of river or waterway from sediment derived from the Project activity.

Standard Operating Procedures

4.1 Refer to the EIA, AEC, latest mitigation measures map approved by the EPD, and ESCP (if any). Check and identify:

    1. Runoff management and sediment control facilities e., temporary earth drains, check dams, silt fences, silt traps, earth bund, and sediment basins etc., to be provided at the site.
    2. Specifications and locations in the  provision of runoff management and sediment control facilities.

4.2 Construct the runoff management and sediment control facilities in accordance with the location and specifications in the EIA, AEC, and ESCP (if any).

Plate 10: Sedimentation pond (pointed)

Figure 9: Plan view of sediment control facilities with cross-sections.

4.3 Prepare a maintenance programme, including plans for removal and disposal of unwanted sediments and repair of damaged runoff management and sediment control facilities.

4.4 Conduct patrolling activities at the project site to check the condition of the runoff management and sediment control facilities at processing, workers quarters and stockpile As a best management practice, cover stockpiles with canvas or other suitable materials, whenever possible.

4.5 Conduct maintenance at regular intervals e. bi-weekly or monthly with increased frequency after each rain event.

4.6 Place excavated sediment from maintenance activities away from riverbanks, waterways, and riparian Compact excavated sediment, provide an earth bund around the sediment to prevent it from being washed away by surface runoff, and divert runoff to a silt trap or sedimentation pond.

4.7 Keep records (with photographs) for any maintenance of the runoff management and sediment control facilities.

4.8 Consider conducting modifications to the runoff management and sediment control facilities in the event of:

    1. Off-site drainage impact (e.g., reduction in flow rate of off- site drainage due to sediment-laden runoff from site)
    2. Repeated failure of the constructed control facilities (usually indicated with murky water discharges)
    3. Changes to on-site conditions.

Conduct the modification after obtaining feedback from EPD.

4.9 Rehabilitate all exposed areas with suitable vegetation.