3. Landfill Waste Acceptance Criteria

Appendix A presents landfill waste acceptance criteria for Class A and Class B landfills for a range of contaminants. These criteria will be included as individual landfill consent conditions imposed by the appropriate regulatory authority. It is the responsibility of the consent holder for each individual landfill to ensure that these conditions are complied with.

The waste acceptance criteria presented in Appendix A have been developed to protect the most sensitive receptor (either drinking water supplies or aquatic ecosystems). There may be other issues of concern for specific wastes, including effects on leachate treatability and the health and safety of waste transporters and landfill operations staff.

Leachate treatability may be assessed by reference to the limit criteria in the New Zealand Standard Trade Waste By-Law (Standards New Zealand, 1999) where leachate is discharged to a municipal wastewater treatment system. Where leachate is treated on-site, site- and process-specific factors will need to be taken into account (Centre for Advanced Engineering, 2000).

The health and safety of waste transporters and landfill operations staff can largely be managed through operational procedures (e.g. controlling dust, the appropriate use of personal protective equipment). Volatile contaminant concentrations should be limited to ensure that Occupational Safety and Health Workplace Exposure Standards (OSH-WES) are not exceeded.

The underlying philosophy is that landfills offering a lower level of environmental protection should be more restricted in the range of wastes they can accept. The process to determine what wastes are acceptable for disposal in each of the differing classes is summarised in Figure 1.

It is recommended that any non-municipal waste streams be checked against the NZ Waste List. Non liquid wastes marked as not hazardous (i.e. non-asterisked) are suitable for disposal to Class A landfills.

Wastes that are marked on the NZ Waste List as being hazardous may be appropriate for disposal at Class A landfills, but only after the landfill operator is confident the waste will not result in leachate from the wastes exceeding the leachate concentrations specified in Appendix A for Class A landfills. Normally this will be assessed using the US EPA TCLP test.

Appendix A provides 'screening limits' for Class A landfills based on the analysis of samples of the waste rather than the TCLP extract. These levels are derived by multiplying the TCLP criteria by 20, based on the assumption that all the contaminant present in the waste is transferred to leachate (which is diluted 20-fold in the TCLP methodology). Where the concentration of the contaminant in the waste is below the screening level, there is no need to test for TCLP. Where the concentration of the contaminant in the waste exceeds the screening level, a TCLP test may show that the contaminant is sufficiently immobilised in the waste matrix to still meet the TCLP criteria.

Some contaminants have low solubility in water but may still pose a risk via leachate discharge where they are present as a separate phase in leachate. Non-volatile hydrocarbons are an example of this.

Wastes marked on the NZ Waste List as being hazardous may be appropriate for disposal at Class B Landfills, but only after the landfill operator is confident the waste will not result in leachate from the wastes exceeding the leachate concentrations specified in Appendix A for Class B landfills. Normally this will be assessed using the US EPA TCLP test.

Appendix A provides 'screening limits' for Class B landfills based on the analysis of samples of the waste rather than the TCLP extract. These levels are derived by multiplying the TCLP criteria by 20, based on the assumption that all the contaminant present in the waste is transferred to leachate (which is diluted 20-fold in the TCLP methodology). Where the concentration of the contaminant in the waste is below the screening level, there is no need to test for TCLP. Where the concentration of the contaminant in the waste exceeds the screening level, a TCLP test may show that the contaminant is sufficiently immobilised in the waste matrix to still meet the TCLP criteria.

Note: cleanfill sites are only able to accept solid wastes that meet the cleanfill definition in the Guide to Managing Cleanfills.

Figure 1: Waste acceptance decision process

The steps illustrated in Figure 1 are explained below.

Step 1. Is the waste prohibited from landfill disposal?

Is the waste included in the list of prohibited wastes?

Step 2. Is the waste a solid?

Does the waste pass the Paint Filter Test? If the waste is a liquid it cannot be disposed to landfill. Alternatives to direct landfill disposal include:

• solidifying the waste, possibly including treatment to immobilise contaminants, prior to disposal
• disposing of the waste to sewer in accordance with the relevant tradewaste controls, possibly including pre-treatment prior to disposal.

Step 3. Does the waste comply with the cleanfill definition?

Is the waste acceptable for disposal to cleanfill? To establish this, check using the cleanfill definition.

Step 4. Is the waste asterisked on the NZ Waste List?

Check the waste stream against the NZ Waste List. If the waste is not marked with an asterisk then it is acceptable for disposal at a Class A or Class B landfill. Waste streams identified on the NZ Waste List as being potentially hazardous are not acceptable for disposal to a cleanfill site, even if they have been treated.

Step 5. Test for total concentration of contaminants in waste and/or Test for concentration of contaminants using TCLP test

If the waste is marked with an asterisk on the NZ Waste List it may still be able to be disposed to a Class A or B landfill without pre-treatment, but only if a total concentration and/or TCLP test shows that the waste meets the relevant disposal criteria specified in Appendix A for Class A and Class B landfills.

The screening criteria are provided as an optional tool for assessing wastes with TCLP criteria, or where contaminant concentration data is already available. If the contaminant concentration is below the screening criteria then no TCLP test is required. Where the contaminant concentration exceeds the screening criteria the waste may still meet the relevant TCLP criteria due to immobilisation of the contaminant in the waste matrix. For contaminants with low solubility, total concentration criteria provide the only waste acceptance criteria.

For wastes with well-defined characteristics, testing may not be required for every load. This is subject to the resource consent conditions for the specific landfill operation and the landfill management plan.

Step 6. Treatment

If the waste is shown by testing to be unacceptable, some form of treatment or immobilisation may be possible to reduce the leachable concentrations to acceptable levels (dilution is not acceptable) for disposal to a Class A or Class B landfill. Cleanfills can not accept treated wastes.