Another endorsement for landfarm activities

27 November 2014

A new study shows that soil ecology and health are not threatened by land-based bioremediation of drilling wastes under the consent conditions imposed by the Taranaki Regional Council.

The report, Biological response of earthworms and soil microbes associated with drilling mud wastes, by Landcare Research, includes both the results of new investigations into drilling muds, and a review of relevant international scientific literature. Its findings include:

• The environmental effects of drilling mud can be explained by the amount of salt present in the mixtures. In simple terms, drilling muds show the toxicity of salt.

• While extremely high levels of hydrocarbons were found to knock back earthworm populations, no mortality was observed at levels even double those that bioremediation sites, known as landfarms, are allowed to apply. Thus there is a good measure of protection.

• The bioremediation process results in marked and rapid reduction in hydrocarbon levels – 80% to 90% within two months, in some cases.

• Hydrocarbons were found to actually enhance soil microbial activity at all except the highest concentrations tested – far above permitted levels.

“The report tells us that the conditions we impose on drilling waste remediation at landfarms are more than adequate to safeguard natural soil degradation processes and re-establishment of earthworm populations,” says the Council’s Director-Environment Quality, Gary Bedford.

He says it is the third in a series of investgiations the Council has commissioned on the way it regulates the remediation of drilling waste on landfarms. “This study started out as a field study on what happens to soil biology during landfarming. But no definitive results could be found in the field so we asked Landcare Research to do some toxicity studies in the laboratory.”

The other reports include one by a leading specialist on contaminated sites, Dr Graeme Proffitt of Pattle Delamore Partners Ltd, who concluded that landfarming is a valid and environmentally acceptable means of waste treatment, and generally appropriate controls are in place. The report made minor recommendations which the Council has adopted.

Another was by soil scientist Dr Doug Edmeades, who assessed whether landfarm soils are fit for pastoral farming, especially dairy farming. He found that concentrations of nutrients, heavy metals and soluble salts in landfarm soils and pasture are similar to normal New Zealand soils, the form of barium present is environmentally benign, and that there is no evidence of accumulation of petrochemical residues.

Most tellingly, he identified worm casts on the sites he visited as ‘the canary in the mine’ indicating that healthy ecosystems had re-established in the soils.

“With the latest Landcare Research study, we’ve now got across-the-board reports on how the process is controlled, what the effects are on the soil ecosystem, and what the end result is,” says Mr Bedford. “And in each case, the findings are reassuring.”

He says the bioremediation of drilling wastes on landfarms turns scrubby, windblown, sandy paddocks into highly productive and valuable pasture, with minimal ecological disturbance. “It is a win-win recycling story.”

The reports are available online at www.trc.govt.nz/reviews-of-landfarming/

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