Before testing soil, set up the ground rules

When Hill Laboratories' Peter Robinson says, "Until everyone knows what the ground rules are, you're wasting your money," the unintentional pun is deadly accurate.

He's talking about the lack of clear guidelines for testing soil - not just in what levels to test for, but also what procedures to follow. Without a standard for things like how samples are to be collected, what depth they're to be collected from, how many are to be collected and how many can be mixed together to make a representative sample of an area, soil consultants are digging blind.

That means they're either going to over-report, possibly resulting in unnecessary extra cost, or they may under-report, meaning the testing may need to be done again.

Robinson says the work companies such as his carry out is the more straightforward part of the process - testing samples for contaminants. A heavy metals and mercury screen (arsenic, cadmium, copper, chromium, mercury, lead, nickel and zinc) costs $84.38 a sample from Hill. An organo-chlorine pesticides test (a suite of 24 organo-chlorine pesticides that includes DD, dieldrin and lindane) costs $101.25 a sample.

The more expensive part of the process is in the work of the consultant who collects the samples and reports on what is found and whether the levels exceed guidelines.

Depending on the size of the property and the number of samples taken - about two cupfuls of soil a sample - the estimated cost is between $2000 and $3000.

Gerard Bird of soil specialists Tonkin Taylor says his company's first response to those seeking testing is to reassure people that soil contamination is not a new problem.

"This is nothing to panic about, it's just something to manage."

He says about 90 per cent of the soil tests they conduct come back within accepted health levels. His advice to those living in suspected contamination areas is to talk to neighbours about sharing costs.

If contamination is found exceeding levels, options include soil removal or covering the affected area. For vegetable gardens, organic gardeners advise building up new soil, avoiding deep digging and not planting deep-rooting vegetables.

A more innovative approach found in this month's issue of the journal Environmental Science and Technology is that pumpkins can cheaply remove DDT from contaminated soil. Zucchini also extracted DDT from the soil well, and rye grass and fescue accumulated the toxin in their roots but did not move the DDT above ground.