Appendix C: Development of total concentration and leachability limits for Class A and Class B landfills
Our approach
The full details of the development of leachability and total concentration limits for Class A landfills is provided in the report Waste Acceptance Criteria for Class A Landfills (URS New Zealand Limited, 2003).
In general, leachability criteria are derived using a target concentration in the receiving environment (drinking water, aquatic ecosystems) and a factor (dilution attenuation factor, or DAF) to account for dilution and attenuation between the landfill and receptor. The criteria adopted for this guideline are as follows.
- Where the US EPA has developed criteria,
these have been adopted:
Target concentration: US Primary Drinking Water Standards
DAF: 100 for all contaminants.
Additional contaminants to be included were selected based on common analytical suites (VOC, SVOC, metals) and the availability of appropriate guideline criteria to be used as target concentrations.
- Where additional contaminants were considered
to be soluble in landfill leachate:
Target concentration: The lower of the NZ Drinking-water Standard or ANZECC freshwater quality criteria
DAF: Constituent-specific DAF based on a 'standard' Class A landfill.
Where contaminants were considered to be insoluble in landfill leachate, leachability criteria are inappropriate and total concentration criteria were developed. These were based on the concentration at which free product would be present in the waste (and therefore likely to be present in the leachate).
