Appendix F: Worked examples

Case study 1: contaminated soil

Soil has been excavated from a former timber treatment site, which is being redeveloped for low-density residential. The contaminant concentrations exceed the residential soil criteria in the timber treatment guidelines (Ministry for the Environment and Ministry of Health, 1997).

Step 1: Is the waste prohibited from landfill disposal? No

Step 2: Is the waste a solid? Yes

Step 3: Does the waste comply with the cleanfill definition? No

Step 4: Is the waste asterisked on the NZ Waste List? Yes: 17 05 03* soil and stones containing hazardous substances

Step 5: Total concentration and/or TCLP test

Existing contaminant concentrations from site investigation report:

The waste material meets the screening concentration for Class A landfills. No TCLP test is required prior to disposal at a Class A landfill.

Case study 2: waste treatment sludge

Wastewater treatment sludge has been obtained from a liquid and hazardous waste treatment operation. The operation accepts a variety of waste streams for treatment prior to disposal/re-use and treats all liquid residues on-site prior to discharge to trade waste and/or landfill.

Step 1: Is the waste prohibited from landfill disposal? No

Step 2: Is the waste a solid? Yes: the sludge is approximately 17 % solids but passes the US EPA Paint Filter test and liberates no free liquids on transport.

Step 3: Does the waste comply with the cleanfill definition? No

Step 4: Is the waste asterisked on the NZ Waste List? Yes: 19 08 13* sludges containing hazardous substances from other treatment of industrial waste water.

Step 5: Total concentration and/or TCLP test

Existing contaminant concentrations from waste treatment operational monitoring:

TPH analysis indicates an elevated level of hydrocarbons (with reference to relevant contaminated site guideline criteria). Further analysis is required to determine suitability for disposal, including consideration of PAH (naphthalene and benzo(a)pyrene) and volatile organics, depending on the source of waste. Naphthalene exceeds screening criteria for Class A landfills, but a TCLP test may indicate that the naphthalene is immobilised in the sludge matrix. Consideration of the TPH results indicates that the hydrocarbons are in the semi-volatile range (i.e. BTEX is unlikely to be an issue).

The TCLP result for naphthalene is below the TCLP criteria for Class A landfills.

Case study 1: historical landfill

ABC Grove Landfill was developed in the mid-1980s and has a design life of 50 years (80-100,000 tonnes per annum). The site was granted resource consent (discharge to air, land and water, divert ...) in 1995 for 25 years' operation. Existing waste acceptance criteria are set out in the consent conditions.

The site meets the criteria for a Class B landfill (existing resource consent) but does not meet the screening criteria for a Class A landfill (no engineered liner, no licensing system, no random inspections).

Determining equivalence with the Class A Landfill Screening Criteria (Appendix D):

1. Use benzene and arsenic in leachate at TCLP criteria concentrations.
2. No liner so modelling of leachate flow through liner not required.
3. 100 m to adjoining river, receptor considered groundwater at 100 m downgradient of landfill boundary

Contaminant parameters:

Model results:

Note: leachate concentrations derived using MfE Model, US EPA TCLP criteria adopted for benzene and arsenic.

Since benzene and arsenic concentrations exceed the criteria for Class A landfills at the receptor, ABC Grove Landfill should use landfill waste acceptance criteria for Class B landfills.