Appendix E: Assessing alternative solutions for Class A landfills
All deviations from the screening criteria in Appendix D should be assessed considering the level of chemical and hydrogeological containment provided by the combination of engineered systems and hydrogeology. The combination of siting and design should result in a level of containment equivalent or superior to a landfill that meets the screening criteria in Appendix D. All Class A landfills must be appropriately sited (see criteria in Appendix D) and have a leachate collection system that is capable of conveying leachate generated in the landfill. Leachate capture should be established through comparison of theoretical leachate generation (including any groundwater ingress) and measured leachate flow.
Equivalence of the liner and natural containment should be considered with reference to:
- resistance to chemical degradation
- hydraulic containment
- chemical containment
- physical strength and deformation characteristics
- general installation procedures
- expected service life.
For the purposes of determining equivalence with the Class A Landfill Screening Criteria, the following assumptions should be made.
- Contaminants are present in leachate at the TCLP criteria concentration (e.g. benzene is present in leachate at 0.5 mg/L).
- Where appropriate, leachate flow through the liner should be assessed using the US EPA's HELP model and appropriate weather parameters.
- Model transport to the closest receptor or to 100 m directly downgradient of the landfill boundary.
- The concentration of contaminants in groundwater at the receptor should be at or below the New Zealand Drinking Water Standard or ANZECC Water Quality Criteria as appropriate [Appendix A specifies through footnotes the target concentration (NZ DWS or ANZECC 2000) used to derive the TCLP Criteria for Class A Landfills.].
