Potential for ground gas

generation, risk assessment and

subsequent design decisions in

absence of national guidelines.

Luke Beirne WasteMINZ conference; 9 November 2017

2

What’s the hazard?

Methane

Odourless and

colourless

Low toxicity, but can

displace oxygen

Flammable/explosive

Carbon dioxide

Odourless and

colourless, acid taste

Asphyxiant

Toxic

3

Tauranga

Waikato

South Auckland

Christchurch

Kapiti Coast

Coastal areas

Former flood plains

Where’s the hazard?

4

Building on marginal land

Creation of preferential pathways

Not considering lateral migration

Not recognising the hazard

How are we exacerbating the problem?

5

Out of sight, out of mind?

6

Not a conventional contaminant

Often missed when not anthropogenic

Only considered from a geotechnical perspective

Late awareness has follow on consequences

Out of sight, out of mind?

7

OHS worker exposure standards

NES “…soil gas sampling to define the extent of contamination by volatile contaminants”

Not included in infrastructure development codes or regional plans

Which code to design to?

Regulatory standpoint.

• 24 townhouses

• Peat previously excavated

• Gas migrating laterally

• Raft foundation

• Gas proof membrane

• Passive ventilation

Residential Development

Papamoa

9

• 115m x 85m mixed use

• Peat capped with engineered fill

• Gas migrating through columns

• Gas proof membrane

• Active ventilation

Commercial Development

Tauranga

11

12

Summary

Widespread source

Poorly recognised hazard

Serious consequences

Regulation needed

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