Waste disposal operations expose areas of bare ground during construction that can result in erosion and silt laden runoff. In some cases runoff from active working areas containing PAF rock has the potential for low pH. Consequently, suitable drainage interception, detention, and treatment facilities are required to minimise the effects on surrounding watercourses.

These facilities include:

• Upstream diversion drains, which divert clean runoff from above the tailings storage facilities
  
  
• Perimeter drains, associated with the perimeter road that encloses the construction area, to direct water to collection and silt ponds
  
  
• Collection ponds, that store runoff from the embankment that can contain potentially low pH water arising from PAF material
  
  
• Silt ponds, which store runoff for a sufficient time to allow any silt to be removed by gravity settling
  
  
• Pumping facilities to pump stored runoff from the collection ponds to the Water Treatment Plant as necessary.

See Water Management for more information.

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1a. Storage Facility Area 1A. 2. Storage Facility Area 2. 3. Decant Pond. 4. Ruahorehore Stream. 5. Ohinemuri River. 6. Water Treatment Plant .7. Ore Processing Plant .8. Collection/Silt Ponds. 9. Perimeter Drains. 10. Upstream Diversion Drains.