There's a fundamental flaw…

There's a fundamental flaw in the proscribed process of measuring the levels of contaminants in soils. The Qualified Person is required to collect representative samples for analysis and submit these to an accredited laboratory. Typically, this is done by collecting 100-200 grams of sample into a bottle which is sent to the lab. This bottle is supposed to contain a representative concentration of contaminants that are present in a particular volume of the site, usually several cubic metres (>5,000,000 grams). Given that soil contaminants are never uniformly distributed in the soil, a 100 - 200 gram lab sample has virtually no chance of being representative of more than 5 million grams of soil! That's bad enough but is made much more serious when we realise the laboratory chemist takes only a 1 to 2 gram sub-sample out of the bottle to do his/her analysis. So, the results that are nicely printed out on a certificate of analysis along with pages of quality control data are based on analysing less than half a teaspoonful of soil and this is accepted as a reliable estimate of the level of contaminants in multiple tons of soil! It isn't. Consider this: if the maximum allowable level of a contaminant is in the low or sub-ppm range---as most of them are---and the contaminant is present as particles mixed among similar particles of natural soil, then 1 particle of contaminant in a million particles of soil analysed will yield a lab result around 1 ppm. However, if the lab is only analysing 1000 - 2000 particles, repeat analyses of this sample will be zero (no contaminant particles in the sub-sample) with the (very) odd sample where a particle happens to be present, 1000 ppm.

We cannot continue to ignore this issue simply because laboratories cannot handle the size of sample needed to get close to being representative. Multiple millions of dollars are being spent chasing exceedences that don't exist while missing exceedences that do.