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Best of WasteMINZ & Ecoforum

These presentations were on quite different topics, having said that, the importance of an accurate conceptual site model was a common  point.

Highlighted was the need to look at contamination in air, particularly where ventiulation systems are present – may need to be included in the conceptual site model.

Main points:

(a) Bringing bioavailability to the fold.

  • Seasonality of elevated arsenic?  This was unclear.  There are still a lot of unknowns with bioavailability and what is happening in the volcanic north island may be quite different from what is happening in the south island.
  • Update to background concs documents, but how would this be done given how specific the areas of elevated arsenic are?
  • There will be other areas of Christchurch with elevated arsenic?  Eg Port Hills volcanic soils
  • How does the elevated arsenic affect landfill disposal options, e.g. cleanfill?

(b) What lies beneath. High Resolution Site Characterisation Tools used ot develop LNAPL Conceptual Site Model. 

This focused on the use of unit volumes of subsurface to avoid excessive averaging of the property and providing detail cirtical for informed decision making.

However, these are expensive tools. Used a lot in Australia but rarely in NZ.  Expensive to bring over. 

(c) Mixed contamination assessment and management at a zinc galvanizing plant

Case study of a site based in Sydney in a mixed land use area, river located to the south.

The investigation found PFAS in just about every stage of the galvanizing process, even when suppliers confirmed their products were PFAS free.The most intersting finding was PFAS on the roof, suggesting that airborne contaminants need to be included in some conceptual site models.  This seemed to be the most significant paway at the site.  However, the process of multiple phases of investigations also led to improvements in the running of the plant as the owners became more aware of how their hazardous substance mmanagement was leading to contamination of soil, stormwater and air.

(d) Correlating asbestos containing material in buldings with concentrations in soil: A New Zealand Based Study.

  • Surface soil scrapes following demolition are a good method to remediate a site without the need for an investigation – go straight to validation sampling. 
  • The ENGEO datset gives an indication what level of asbestos is likely to be found based on the properties of the site structure, and the results are not surprising.  For example, 1960s properties gave greatest likelihood for HH significant results in surrounding soil.
  • Asbestos ‘super 6’ roof data set is high risk based on the results obtained, therfore more sampling would be good at known high risk sites to delineate this risk?
  • The ENGEO study has lead to Auckland Council (AC) now requesting testing for asbestos routinely with pre – 2000s properties. However, the audience was unclear how AC can justify requiring testing for asbestos - what is the legal reason that would require this.  More likely than not legal test (>50%) only exceeded for the most high risk sites (1960s).
  • There are still plenty of other variables that would affect asbestos in soil, eg use of sander.

Context, the results are unlikely to give asbestos in air non compliances as the affected area is so limited.  We need to be careful not to remediate when this is not necessary.

However, disposal of excess soil will still be an issue – haven’t ceritified the soil is asbestos free.

It was noted that the difficulty getting expensive tools into NZ for our cheap and cheerful investigations is an ongoing issue.

In the spirit of improving processes, all four presentations focussed on looking at your results in detail to get suitable remediation strategies, or obtaining more in depth information on a site before deciding on the remedial action plan.

Presenter Name Presenter Company

Dave Bull

Nicola Peacock

HAIL Environmental

Malloch Environmental

Tim Mulliner AECOM
Mark Ballard GHD
Daniel Kaminski ENGEO

8 October 2019 New Zealand Branch report by Helen Davies - AURECON

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