They just wanted a nice green lawn

When Lana Sanders moved into her new Otahuhu home in 1975 her lawn was little more than a compacted square of volcanic gravel.

She and her husband Ken were keen on having a lawn so they ordered in a truckload of topsoil, which they spread over the gravel with a wheelbarrow and shovel.

Today the couple have a wonderful lawn - but there is a good chance that the soil it is growing on came from an old horticultural site covered in toxic pesticides.

During the 60s and 70s it was common practice for contractors to buy topsoil from subdivisions on the outskirts of town and sell the dirt for gardens.

Now hundreds of Auckland residents, who weren't identified as being affected by a council study, are wondering if their backyards are also contaminated.

"Any gardener in Auckland with a clay [or gravel] section would have done the same thing and got soil in," said Lana Sanders. "But where did that soil come from?"

She believes tagging LIM reports about possible soil contamination is pointless.

"It's so hit and miss. I honestly can't see how they can mark a LIM when, let's face it, the contamination could be anywhere and everywhere."

Contractors the Weekend Herald spoke to agreed that buying topsoil from subdivisions was common.

West Auckland man Mate Milich recalls transporting truckloads of soil from subdivisions during the 1960s.

"It was surplus stuff. You had to get rid of it, onsell it - whatever."

Most of his deliveries were to city council parks.

"I would buy a big heap of soil ... and then sell it to the council for parks. It came from areas where there were market gardens and orchards. We would deliver it and put it on the parks."

Auckland city and regional councils say records were never kept of the widespread practice of selling subdivision soil for residential use. They have no way of knowing where it ended up around the city.

But it is not just old topsoil sales that are presenting a problem.

One West Auckland real estate agent had a $300,000 contract fall over earlier this week after the vendor refused to get a test done because his house had been built three years ago on new topsoil.

"The vendor said `stick it up your nose' basically because he had brought in new topsoil and he couldn't believe there would be an issue."

That vendor is probably right. In recent years councils have required soil testing on subdivisions, meaning most topsoil will have been checked before being sold.

Central Soils manager Paul Forlong said no one need worry about buying contaminated soil these days because subdividers would have screened it before buying it.

If the soil was found to have higher-than-acceptable levels of contaminants it would not be sold.