CHELSEA BOYLE
The environmental consultant who investigated arsenic contamination in Carterton has said the really effective way of remediating soil contaminated with arsenic was to put it in a secure landfill “where it is just going to be buried forever”.
“It doesn’t matter how deep as long as it is covered and not accessible.”
Ted Taylor has been an environmental chemist field for over 40 years, and was commissioned by Heidi and Rupert Holbrook to complete a detailed site investigation in 2015 regarding a historic sheep dip on their property.
On that site “the arsenic was the overriding issue”, Mr Taylor said.
Arsenic is an element and does not just disappear, but depending on soil type it can move, he said.
“But generally, it will basically stay, roughly attached, within the soil structure,” Mr Taylor said.
Mr Taylor’s report revealed an arsenic concentration of 530mg/kg near the woolshed at a depth of 0-15cm, which is 31 times the nationally recommended health standard of 17mg/kg for a lifestyle block.
The area surrounding the woolshed also breached the recommended level.
Six soil samples recorded between 138mg/kg and 380mg/kg in the paddock near the family home.
Mr Taylor said the soil samples had been taken in a grid pattern so they could rule out which areas breached the health standards.
“Obviously, the samples are spot samples, but the grid builds up a picture,” he said.
“The whole idea of doing a grid thing is so you can basically delineate the area that is over the 17mg/kg and the ones that are outside that.”
It was clear the high readings were around the sheep dip.
Mr Taylor said it was not unusual to have such high readings near an old sheep dip.
“If you look around the country you will find there are other areas close to woolsheds that have quite high concentrations as well.”
DDT and Dieldrin, organochloride pesticides, were also investigated on the site, but did not breach the national health standards.
Unlike arsenic, they are both biodegradable but you still would not want to have residuals in the soil, Mr Taylor said.
Historically, DDT was used to kill insects, which was drawn to people’s attention in Rachel Carson’s 1962 book Silent Spring he said.
“DDT was found to be going through the food chain, it gets into the fat system in animals and people,” he said.
“So if you have hens eating in an area where there is DDT, DDT can end up in the eggs.
“You don’t want poultry around it.”
He said generally when it came to woolsheds arsenic is the one that is going to be the more long-term concern,”
Arsenic could be mixed with other soil to dilute it to a point it met health standards.
MANY SHEEP DIP SITES REMAIN UNKNOWN
Greater Wellington Regional Council Environmental Science team leader Philippa Crisp said they could not say how many sheep dips were in Wairarapa but they were adding sites to the Hazardous Activities and Industries List (HAIL) all the time.
“At the moment, we don’t have every single sheep dip in Wairarapa.”
There were 2376 HAIL sites in the whole of the Wellington region and 441 in Wairarapa, she said.
But that included things like petrol stations and gun clubs.
It also included land where it was thought hazardous industrial activity had happened in the past.
Recently they had been trying to identify more historic orchard sites, but they had to have evidence, she said.
HAIL sites were recorded on a database that is open to the territorial local authorities, she said.
The territorial authorities would usually put that information on people’s LIM reports.
If something was listed as a HAIL site that would automatically trigger the National Environmental Standard for Assessing and Managing Contaminants in Soil to Protect Human Health before a subdivision could take place.
In Wairarapa the two biggest categories of listed HAIL sites were chemical storage including timber treatment and motor vehicle workshops.
