While rehabilitation methods that disturb soil and damage remaining vegetation are still widely used, the industry appears to be turning to low impact approaches that focus on ecological longevity while increasing profitability.
Lake Macquarie-based operations manager for SNK Group Wayne Walshe is responsible for managing mine surface support for five underground coal mines in the Newcastle area.
According to Walshe, the five underground coal mines he works for are located under an environmentally sensitive forest that requires special care.
“We’ve done a lot of subsidence repairs over the years and the traditional approach was to bring in a bulldozer or large excavator to repair the cracks causing significant disturbance to the area. But we couldn’t justify the damage that would cause in this environment, so we adopted a minimal disturbance and source control philosophy,” Walshe said
“From this we identified erosion control as one of the biggest challenges to successful rehabilitation. Trialling several techniques we brought in a hydroseeder and looked closely at the mulches we used.”
Hydromulching is particularly useful for revegetation of disturbed areas, especially on slopes where there is a significant risk of erosion occurring during the period of initial plant establishment.
One particular SNK mine is especially close to the surface and the area experiences significant surface cracking.
“Mine subsidence is a major issue for all mining companies and as part of their licence requirements they must minimise their impact on the environment. As most of the operations we deal with operate under public land, it’s important we deal with any subsidence event quickly. Safety of the public and mine is paramount,” Walshe said.
“With a hydroseeder we have a small machine that gives us good access. We can spray woodfibre mulch on a targeted area to start revegetation quickly and effectively.
“We disturb as little soil as possible, and then hydroseed and hydromulch the whole area for soil protection. We’re really happy with the results and now we only need to send out two labourers; one to operate the hydroseeder and the other to drive the truck it sits on. The entire job takes much less time and fewer people; everyone wins.”
According to Walshe, access is no longer an issue because the accuracy a hydroseeder machine provides means large areas of awkward ground that were not able to be driven on or accessed can now be sprayed from a distance.
“We can cover a big area fast,” he said.
Wally Buttman of US based mulch company Profile Products said using a hydroseeder is much like comparing hand painting with spray painting.
“Where access is difficult, whether in mines, on hillsides, slopes or ditches, landfills, or large construction sites, a hydroseeder gives greater accessibility, speed and accuracy,” he said.
Additionally, Peter Carmichael general manager of Brisbane-based Revolution Equipment said these days the cost to the environment is part of a contractor’s responsibility.
“We find the best final result is achieved when there is regular use of effective revegetation techniques throughout the lifetime of the mine,” he said.
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