Local Govt | National News Video | Parliament Headlines | Politics Headlines | Search

 


Report Finds Low Risk Of Contamination


MEDIA RELEASE
January 29, 2013

Report Finds Low Risk Of Contamination

Environment Canterbury has released a report and recommendations on managing the possible risk to Christchurch drinking water from treated timber piles used in building foundations.

“The aim of the report was to better understand the possible risk to Christchurch’s drinking water from leaching of treated timber piles before construction work starts in TC3 areas,” said Ken Taylor, Environment Canterbury’s Director Investigations and Monitoring.

“The report informs councils, government agencies and builders of the issue so they can take the necessary steps to minimise any risk to Christchurch’s drinking water.”

The Environment Canterbury study – Groundwater quality risk assessment for treated timber housing foundations used in the Christchurch rebuild – was completed with help and information from the building industry, CERA and the Ministry of Business, Innovation and Employment.

“The report found there is generally a low risk to groundwater quality throughout Christchurch because in most areas the drinking water aquifers are much deeper than any potential piling from building construction.”

The maximum economic depth for treated timber piles is reported to be 12 metres.

As a result the report looked for at-risk areas of TC3 land in Christchurch where the main groundwater aquifer was less than 13 metres deep – which allows for the maximum pile depth of 12m plus a 1m buffer.

The report found – based on worse-case scenario modelling and a literature review – there was a possible risk to groundwater quality in shallow gravels from leaching of the chemicals most commonly used to treat timber piles.

“In the TC3 areas where the gravel beds are close to the surface, the report recommended minimising the use of copper chromium arsenic (CCA) treated timber piles.

“As an alternative, steel or concrete or non-CCA treated wooden pile foundations can be used to minimise the risk to groundwater.”

Concrete and steel are relatively inert – compared with treated timber – with a low risk of contamination of groundwater.

The locations where both TC3 land and shallow gravels coincide are limited to small areas in Kaiapoi, in Hoon Hay, and near Prebbleton (see figure 4-1 in the report).

“Any risk to Christchurch’s drinking water from deep piling of treated timber can be minimised by good practice and co-operation between agencies and builders, now that we have this report and recommendations,” said Ken Taylor.

Mike Stannard, Chief Engineer Building System Improvement Programme, said MBIE will consider the findings and recommendations in the Environment Canterbury report, which will inform MBIE’s next update for repairing and rebuilding houses in Canterbury.

Technical facts

TC3 land in Christchurch is likely to sustain moderate to significant liquefaction damage in an earthquake. As a result any new buildings on TC3 land will require site improvements, deep piles, or surface structures with shallow foundations. The best option will depend on a site-specific geotechnical investigation.

The CCA treated timber likely to be used in deep piling is treated to hazard class 5 and contains a mixture of copper, chromium, and arsenic. These chemicals can leach into both soil and groundwater.

Worse-case modelling showed the arsenic concentration leaching from a row of 20 piles would be between 0.0047 and 0.009 mg/L (at a distance between 22 and 29 metres downstream and with a 1 metre per second aquifer flow) which is below the maximum acceptable value for drinking water of 0.01 mg/L.

For more information
http://ecan.govt.nz/publications/Reports/quality-risk-treated-timber-housing.pdf

ENDS

© Scoop Media

 
 
 
 
 
Parliament Headlines | Politics Headlines | Regional Headlines

InternetNZ On Snowden Docs: Mass Collection Of Pacific Data Affects Kiwi Holidaymakers

The allegation that New Zealand has conducted mass data harvesting on its Pacific Island neighbours raises concerns about New Zealanders’ communications being collected, says InternetNZ.

“If the allegations are correct, then New Zealand would be mining data about everyone in the Pacific Islands named in the allegations. That’s everyone. Not just individuals who attract specific surveillance warrants, but everyone. This means local residents to visiting Kiwi tourists could be having their data collected." More>>

 

PARLIAMENT TODAY:

Teina Pora Wins Appeal: Gordon Campbell On The Privy Council Decision

The quashing of the convictions of Teina Pora for the rape and murder of Susan Burdett in 1992 has shone a spotlight once again on a major gap in the New Zealand justice system... More>>

ALSO:

Urgent Bill Planned: MP Pay Rises To Match Public Service

Prime Minister John Key today announced an overhaul of the Remuneration Authority Act, tying MP salaries to those of the wider public sector, which will be passed under urgency. More>>

ALSO:

PM's Press Conference: MP Pay Rises, Solid Energy, Iraq

Prime Minister John Key answered questions in his Post-Cabinet press conference about the Iraq deployment, Solid Energy and National’s decision to overhaul the Remuneration Authority Act. More>>

ALSO:

Worksafe: MSD Charged Over Work And Income Ashburton Shooting

WorkSafe NZ has laid one charge against the Ministry of Social Development (MSD) in relation to the shooting at the MSD Ashburton office on 1 September 2014 in which two Work and Income staff were killed and another was injured. More>>

ALSO:

Iraq: Ex-Hostage Says Government Not Putting NZers, Iraqis First

Harmeet Singh Sooden is travelling to Iraq in the coming weeks to work with Christian Peacemaker Teams (CPT) on a short-term assignment. More>>

ALSO:

Joint Statement: Australia-New Zealand Leaders’ Meeting

Prime Minister Key warmly welcomed Prime Minister Abbott and Mrs Abbott to New Zealand. The visit has enabled wide-ranging and substantive discussion that has underlined the strength, value, diversity and warmth of our trans-Tasman relationship. More>>

ALSO:

Press Conference: Peters To Stand In Northland By-Election

New Zealand First Leader Winston Peters has announced his intention to stand in the Northland by-election, citing his own links to the electorate and ongoing neglect of the region by central government. More>>

ALSO:

Get More From Scoop

 

LATEST HEADLINES

 
 
 
 
 
 
 
 
Regional
Search Scoop  
 
 
Powered by Vodafone
NZ independent news