Latest News & Public Notices

Moanataiari Project: Update # 26: Governance Group approve arsenic bioavailability trial

03 May 2012

At its meeting held on 2 May 2012, the project Governance Group made a decision to change phase three of the project from "natural background testing" to a "health risk assessment".

"The natural background phase, while useful to help determine what remedial options were practical for Moanataiari, does not answer fundamental questions regarding the risks to human health" said Communications Manager Benjamin Day.

"The Governance Group have decided that, with limited resources, the focus of the project must continue to be about human health, which is why they have decided to change phase three from a background study to a Health Risk Assessment (HRA) trial to find out more about arsenic's bioavailability in the soil".

"Basically, if the trial finds that the arsenic is not absorbed very readily by the body (low bioavailability), then the remediation threshold could be higher than the National Environmental Standard (NES) of 20 parts per million (ppm) for residential properties at Moanataiari".

"On the other hand, if the trial finds that the arsenic is absorbed quite readily by the body (high bioavailability), then the remediation threshold could be a lot closer to the National Environmental Standard (NES) of 20 parts per million (ppm) for residential properties".

The trial could be extended to a broader HRA project once the results are known from the smaller scale trial due to start later this month.

Arsenic is the predominant element that has been found across the subdivision during phase two of the project. Properties with high concentrations of lead or other heavy metals will be assessed using other health criteria to ensure all contaminants are considered before remedial options are recommended for each property.


HRA Key Facts

  • Bioavailability simply means how much of the arsenic in the soil (if ingested) is actually absorbed by the body
  • The National Environmental Standards (NES) assume the arsenic in the soil is 100% bioavailable once ingested, which is part of the formula used to get to the standard of 20ppm figure (arsenic) for residential properties
  • If the bioavailability of arsenic in the soil is found to be low (10-20%), this will increase the risk threshold and therefore the remediation criteria will be higher than the NES standard of 20ppm
  • If the bioavailability of arsenic in the soil is found to be high (80-100%), this will reduce the risk threshold and therefore the remediation criteria will be close to the NES standard of 20ppm

With these points in mind, the HRA will therefore be able to assist the project in the generation of remediation criteria and management/remediation options for phase four of the project.


Estimated timelines for phase 3

  • May/June 2012 initial HRA trial
  • June/July 2012 - Governance Group decision to extend trial to a full HRA phase

Property owners and tenants will receive their property reports from phase two of the project by June 2012.

 


 

Project plan summary

Phase One - Initial Testing Programme

COMPLETED

Phase Two - Moanataiari Private Property Testing
  • 13 January 2012 COMPLETED
    Tenders close for testing programme contractor - begin booking 'testing' appointments
  • 24 January 2012 COMPLETED
    Tender awarded (by Governance Group)
  • 25 January 2012 COMPLETED
    Contractor on-site, begins work programme
  • 15 May 2012 COMPLETED
    Testing completed and raw data sent to residents
  • June 2012
    Final property reports completed
  • June/July 2012 
    Communication with individual property owners about their results
Phase Three - Health Risk Assessment
  • May/June 2012 initial HRA trial
  • June/July 2012 - Governance Group decision to extend trial to a full HRA
Phase Four - Response Action Planning
  • July 2012 - September 2012
  • September 2012 - Communication with individual property owners about their results
Phase Five - Remedial Works
  • September 2012 - January 2013 (New funding application, planning, tenders etc)
  • January 2013 - July 2013 - Physical works