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Liquid wastes from construction sites are a significant pollution problem and should be minimised. Mud and silt from uncontrolled run-off is the most common pollutant, but adverse weather may also result in ruining or relocation of materials and wastes.

Construction-site pollutants and their causes are:

Construction site pollutants



Run-off from cut and fill areas


Spills and leaks


Wash-off from formwork and machinery


Wash-off from formwork

Don't mix the drains!

  • liquid.jpgStormwater drains are for clean rainwater only, as it goes directly into watercourses: streams, lakes, harbours and beaches. Stormwater is untreated. Discharging pollutants into stormwater drains is illegal, unless you have resource consent or it is a permitted activity. Stormwater can be contaminated by particles and chemicals that leach from C&D waste.
  • Wastewater drains or sewers are for blackwater (i.e. sewage) and trade wastes only. It is treated before going into watercourses.

Make sure all site workers know the difference. Spills can be very costly for the polluter.

Dealing with liquid pollution

  • Have a dedicated wash-down area.
  • Use bunds or drip trays to prevent leak and spill contamination.
  • Use gravel areas, silt fences, swales or ponds for silt containment.
  • Install oil and grease interceptors.
  • Make sure paint left-overs are dry before disposing with solid wastes.

Plan ahead

  • Draw up a drainage plan for your site.
  • Ensure that any stored liquid materials are safe and secure.
  • Have a spill kit for fixing and effectively dealing with spills on site.
  • Write a spill procedure plan to deal with accidents.
  • Have regular inspections and maintenance.