9 November 2020
Trialling topsoil alternatives at Maules Creek
Amid one of the driest periods on record in North West NSW, a trial of a topsoil substitute novel to the mining sector has delivered a range of positive environmental outcomes at our Maules Creek mine.
Hydromulch – a biodegradable mix of paper or wood fibres, seeds and fertiliser – creates a hard surface that holds in seeds and nutrients. Hydromulch can be used to create a seed bed in areas where you might not ordinarily be able to have one, and while it is commonly used in civil construction, the mixture is less common in the mining industry.
Hydromulch uniformly distributes seeds and ensures that they bond to the surface, which means they’re less likely to be washed away during rainfall or blown away in the
wind. It also creates a microclimate conducive to the seed establishing and forming a vegetative cover.
This cover, in turn, helps stabilise slopes. An established topsoil layer, or substitute in the form of hydromulch, has the added benefit of controlling erosion and suppressing dust, particularly relevant during periods of drought. We wanted to see if hydromulch could be used to establish a topsoil cover on steep slopes where regular topsoil placement may have some potential to experience erosion.
Starting in June 2019, we used hydromulch on one part of the steep mine boundary at our Maules Creek mine, then compared that to an adjacent area where we used regular topsoil. The trial area was difficult to access with equipment, and the slope was reflective of the peaks and troughs that will form part of the final landform once mining ends at Maules Creek.
There was no rainfall until February 2020. However, when the rain did fall, vegetation grew in the hydromulch trial area. The hydromulch appeared to protect the vast majority of the seeds.
Hydromulch also limits dirty water run-off, as water isn’t flowing over dirt. The hydromulch in the trial created a sealed surface that remained intact until the vegetation began to grow.
These promising early results suggest that hydromulch could be used as a topsoil substitute to stabilise slopes; minimise dust and dirty water run-off; and establish vegetation, particularly during dry periods. We will consider using hydromulch as part of our rehabilitation and other environmental management strategies.Back to News