Post on 29-Sep-2020
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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