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

 

Parliament Today:

Werewolf: The Defence Pretence

Last year, the world began spending more money on weapons again, for the first time since 2011... New Zealand belongs to a region – Asia and Oceania – where military spending rose sharply in 2015, by 5.4 per cent. More>>

ALSO:

Gordon Campbell: On Not Crying Foul, Argentina

So a couple of guys found to be criminally liable of environmental pollution in Argentina lodge an application with the Overseas Investment Office… in order to buy some prime New Zealand rural land. Seems that their factory back home had carelessly and/or intentionally discharged toxic waste into the Lujan river. Bummer... More>>

ALSO:

Urban & Rural: $303m To Merge And Modernise New Zealand’s Fire Services

Internal Affairs Minister Peter Dunne today announced funding of $303 million over five years to combine urban and rural fire services into one organisation from mid-2017. More>>

ALSO:

High Trust Regime: What Did The PM Tell His Lawyer About Foreign Trusts?

The Government stopped the IRD from reviewing New Zealand foreign trusts shortly after the Prime Minister’s lawyer wrote to the Revenue Minister claiming John Key had promised him the regime would not be changed. More>>

ALSO:

Road Crime: Wicked Campers Vans Classified As Objectionable

The definition of publication includes any "thing that has printed or impressed upon it, or otherwise shown upon it, 1 or more (or a combination of 1 or more) images, representations, signs, statements, or words", The Classification Office has previously classified such 'things' as billboards, t-shirts, and even a drink can. This is the first time the Classification Office has classified a vehicle. More>>

ALSO:

'When New' Repairs: Landmark EQC Settlement

The Earthquake Commission has cut a deal with 98 Canterbury homeowners that affirms the government entity's responsibility to repair earthquake-damaged property to a 'when new' state, as well as covering repairs for undamaged parts of a property and clarifying its position on cash settlement calculations. More>>

ALSO:

Gordon Campbell: On Kiwirail’s Latest Stint In The Dogbox

The denigration of Kiwirail continues. The latest review (based on a 2014 assessment) of the options facing the company have enabled Kiwirail to be hung out to dry once again as a liability and burden on the taxpayer. More>>

ALSO:

Royal Society Report: Good Opportunities To Act Now On Climate Change

There are many actions New Zealand can and should take now to reduce the threat of climate change and transition to a low-carbon economy, a report released today by the Royal Society of New Zealand finds... More>>

ALSO:

Get More From Scoop

 

LATEST HEADLINES

 
 
 
 
 
 
 
 
 
Regional
Search Scoop  
 
 
Powered by Vodafone
NZ independent news