Cleanfill landfills are not designed in the same way as other landfills.

Cleanfill landfills can only accept ‘clean’ material for disposal, which is material that should not impact human or environmental health. They don’t have leachate collection systems, for example, so it is important that cleanfills only contain contamination-free material. 

Cleanfill material includes: 

1. Natural materials such as clay, soil and rock 
2. Some manufactured materials like concrete, brick or tiles

Cleanfill material must not include:

• Components that can burn, decay, degrade or leach into the environment (for example, timber, greenwaste, household rubbish) 
• Hazardous substances or products derived from the treatment of hazardous waste 
• Any liquid waste 
• Contaminated materials (for example, contaminated soil, road sweepings, foundry sand) 

Soils can contain potentially toxic elements and organic compounds at levels that are considered contaminated. At high enough concentrations, these contaminants can be toxic to human and environmental health. Contaminated soils should not be accepted at cleanfill landfills.  

The reason for contamination can often be because chemicals in the past were manufactured, used, stored and disposed of in ways that are now unacceptable. For example, the historically used and environmentally detrimental pesticide, Dichlorodiphenyltrichloroethane (known as DDT), has accumulated in areas of frequent past use but should not exceed 0.35 mg/kg (including all DDT isomers and metabolites) in rural areas if it is to be considered for cleanfill disposal. Other manufactured chemicals should not be detectable when analysed.  

Soil from sites with a history of hazardous activities may be contaminated. The types of activities that involve hazardous substances are outlined in the Ministry for the Environment’s Hazardous Activities and Industries List (HAIL). Any soil accepted from a HAIL site should be tested to make sure it is not contaminated.

Soils naturally contain a range of elements that occur in the environment at low concentrations but can become human and environmental health concerns when elevated. These potentially toxic elements include common heavy metals and metalloids. For soil to be considered ‘clean’ and acceptable for cleanfill disposal, the concentration of these elements should be within the range that occurs naturally in the disposal area.

The national predicted background concentration (PBC) dataset developed by Manaaki Whenua Landcare Research in 2015 and updated in 2023 was intended for this exact use. The PBC dataset uses the median (i.e., 50%), 90%, 95% and 99% percentiles as concentration ‘cut-offs’. The 99% percentile is to be used for assessment of whether elements meet background levels, according to the 2023 WasteMINZ Guidelines. However, any potentially toxic element with concentrations predicted at or above the 95% percentile is expected to likely be naturally elevated due to geogenic processes. In these areas, concentrations may also vary significantly at smaller scales than captured in the predictions and site-specific assessment of background concentrations is suggested to be warranted. In Otago, 15% of the region is predicted to be naturally elevated in arsenic.

The table below shows how much of the predicted background concentration percentile ranges are expected in Otago and the threshold for background concentrations of different potentially toxic elements using the up-to-date dataset.

^a Extent of each percentile range relative to the total area in Otago.
^b Site specific assessment of background concentrations may be required.

The Regional Plan: Waste allows for cleanfill landfills to operate as a permitted activity, as long as:

• They have effective measures in place to control erosion and sediment, ensuring sediment does not enter a water body.  
• They only accept cleanfill material. This might mean they need to monitor incoming loads to make sure they do not contain unacceptable materials.  

If these requirements are not met, a consent is required. A consent application may be declined if the location of the landfill or material accepted is not suitable. If you have any questions, please call 0800 474 082 and ask to speak with someone in our consents team.