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

Patience: Drive Safe

Be patient before passing is the AA's message for drivers this Labour weekend.

"People taking crazy risks to get past other vehicles is one of the most dangerous things on the road,” says AA spokesperson Dylan Thomsen.

“The weather is looking good for the long weekend so the roads will be busy. Unfortunately, that also increases the chances of people getting frustrated and trying a risky passing manoeuvre. When they get past, there will probably be more traffic up ahead anyway so it won’t get people there faster.” More>>

 
 

Parliament Today:

Employment Relations Bill: Govt Strains To Get Tea Break Law Through

The Government has been left with egg on its face - failing to get its much-vaunted, but hugely unpopular, meal break law passed in the first week of its new term, Labour spokesperson on Labour Issues Andrew Little says. More>>

ALSO:

Guns: Police Association Call To Arm Police Full Time

"The new minister gave his view, that Police do not need to be armed, while standing on the forecourt of parliament. The dark irony was that the interview followed immediately after breaking news of a gunman running amok in the Canadian parliament in Ottawa..." More>>

ALSO:

Gordon Campbell: On The Tokenism Of New Zealand's Role Against Islamic State

Our contribution against IS will be to send SAS forces to train the Iraqis? That’s like offering trainers to General Custer just as the 7th cavalry reached the Little Big Horn. More>>

ALSO:

Scoop Business: Shell And Todd Caught Drilling Without Approval

Multi-national oil company Shell’s New Zealand arm and local energy giant Todd Energy have breached the new law governing New Zealand’s Exclusive Economic Zone, the Environmental Protection Authority says in an Oct. 10 document released by the Green Party. More>>

ALSO:

Gordon Campbell: On Pharmac, Gough Whitlam And Sleater-Kinney

We’re not at the outset of these negotiations. The outset was six years ago, and negotiators were hoping to have some sort of ‘framework’ deal finished in time for the APEC meeting in a few weeks’ time. These ‘extreme’ positions are what we’ve reached near the intended end of the negotiations… More>>

ALSO:

PM Of Many Hats: Questions, No Answers On Whale Oil

Dr RUSSEL NORMAN (Co-Leader – Green) to the Prime Minister: How many times since November 2008 has he spoken with blogger Cameron Slater on the phone and how many times, if any, has he texted him?
Rt Hon JOHN KEY (Prime Minister): None in my capacity as Prime Minister. More>>

ALSO:

Aussie Investigation Dropped: Call On Minister McCully To Pursue The Case Of Balibo Five

West Papua Action is deeply concerned at the lack of any clear outcome from the Australian Federal Police inquiry into the 1975 deaths of the ‘Balibo Five’ including NZ journalist Gary Cunningham. More>>

ALSO:

'Feed The Kids' Bill: Metiria Turei To Lead Fight On Feeding Hungry Children

Green Party Co-leader Metiria Turei is urging all political parties to support the Feed the Kids Bill which she inherited today from Mana leader Hone Harawira. More>>

ALSO:

Parliament Today: State Opening Of Parliament

The House sat at 10.30am on Tuesday before MPs were summoned to hear the Speech from the Throne in the Legislative Council Chamber. More>>

ALSO:

Get More From Scoop

 

LATEST HEADLINES

 
 
 
 
 
 
 
 
Regional
Search Scoop  
 
 
Powered by Vodafone
NZ independent news