South African legislation, as is the case of most other countries, requires that all mine planning should be conducted with closure in mind. Part of this planning is to provide funds for closure and Petra has therefore been evaluating ways to reduce its closure liabilities by conducting concurrent rehabilitation.
In 2017 and 2018, the Finsch mine started to rehabilitate an area referred to as “the Old Paddocks”, which was formerly used at the mine site for slimes disposal.
The Old Paddocks were reshaped, stockpiled top soil was applied and revegetated with native grass species in order to gain long-term soil stability. A series of storm water structures were also constructed in order to ensure proper drainage and stability of the site. The Old Paddocks were quite heavily overgrown with Prosopis glandulosa (honey mesquite, an alien invasive species in South Africa), but as part of the rehabilitation project these plants were eradicated to a large extent.
The revegetation was not so successful initially due to the drought conditions experienced in 2017 and the paddocks were therefore re-seeded the following year. In 2019 the first Land Function Analysis was conducted on the rehabilitated area to serve as baseline for measuring rehabilitation success. The baseline study indicated good stability (59%) in the substrate, mostly due to the banded ironstone top cover. This top cover unfortunately also resulted in a low infiltration value, but it is expected to improve as the plant roots loosen the compacted substrate. The site also showed the lowest nutrient value as this is a newly rehabilitated area and the grass species have only started to grow.
This rehabilitation project successfully reduced the mine’s rehabilitation liability by ZAR12 million (US$765,428) and shows potential in becoming a sustainable land function in the greater habitat around the mine, by increasing biodiversity and reducing alien invasive plant species.