Asbestos mountain fills Kate Valley
More than 32,000 tonnes of asbestos-contaminated waste has been buried deep in North Canterbury.
The asbestos-contaminated waste makes up about 1.5 per cent of the 2.32 million tonnes of waste disposed of at Kate Valley landfill since it opened in 2005, with most of asbestos-contaminated waste buried since the earthquakes.
Most of that waste is in the form of soil, gravel or rubble that has, or may have been, exposed to asbestos during the earthquakes or demolition.
If a building is identified as having a risk of asbestos then a specialist contractor, on behalf of the demolition contractor, takes the waste to Kate Valley in plastic lined and covered bins - it is usually also "wetted down" at the time of loading to minimise airborne dust.
Upon arrival at the landfill, the waste is tipped almost immediately into a trench then buried by an excavator waiting on site.
The Health and Safety in Employment (Asbestos) Regulations 1998 state all asbestos waste is to be buried in a designated area within a managed refuse disposal site, and covered with at least one metre of earth.
Transpacific Industries Ltd landfill manager Rangi Lord said the landfill was triple-lined to prevent anything contaminating the surrounding soil, while asbestos-related waste was buried an average of four metres deep in a specifically dug hole.
"It is also surveyed so we know where it is and not to go back digging there in the future," he said. "We make no apologies for being overly cautious."
Lord estimated 900 tonnes of asbestos-related waste was processed monthly.
Transwaste Canterbury chairman Gill Cox said as the demolition started ramping up in central Christchurch the amount of asbestos-related waste had increased significantly.
There was no harm to the environment or people once it was buried as it was only dangerous when the fibres were airborne.
"The biggest thing for us, absolutely, is health and safety," Cox said
"That's the number one priority over everything."
Independent air quality monitoring is regularly done at the landfill, specifically checking for airborne asbestos fibre. To date, all tests have been clear.
Canterbury District Health Board medical officer of health Alistair Humphrey said asbestos was not harmful once buried.
"I don't think it ever loses completely it's potential . . . if it were to be dried out and dug out and cut again, then yes, it could become dangerous again," he said.
Asbestos, a known carcinogen, can cause mesothelioma, a rare fatal cancer of the lining of lungs or abdominal cavity, lung cancer, asbestosis or scarring of lung tissue, and pleural plaques.
The register of asbestos-related illnesses between 1992 and 2012 had about 1300 cases, 99 per cent of which were due to prolonged exposure to asbestos in the workplace, Humphrey said.