One of New Zealand’s largest mines, the Stockton mine, is the scene of large-scale site rehabilitation into indigenous subalpine shrubland typical of the West Coast plateau landscape. Success stems from more than a decade of research into optimum growth medium and planting methods.
Coal mining on the Stockton plateau near Westport has been taking place since the late 1800s, where early operations were underground. The site has seen several changes in ownership since that time, most recently Solid Energy until August 2017, and then BT Mining. The 65/35 joint venture of Bathurst Resources and Talley’s Energy now produces around 1.2 million tonnes a year of premium-quality export coking coal for steelmaking at this site.
At the site of the Stockton mine, more than 1000 hectares have been disturbed over time, which is a large area as mines go in New Zealand. The plateau is in a harsh climate, at 500 metres to 1100m above sea level, and rainfall of 5-6 metres per year. Bathurst loses 30% of working days on average because of low cloud and fog, reducing visibility on site to less than 60m. This affects site rehabilitation techniques to restore ground cover, and manage acidic runoff into waterways.
Compounding the challenge for the current mine operator is a legacy of decades of mining with little or no regard for environmental effects. The need to blend variable coal quality from different pits to meet client requirements had led to an unsystematic opening up of the site. Mining practices now attend to water quality, indigenous habitat restoration, and off-site conservation programmes.
Bathurst today employs around 250 staff at Stockton, close to all of whom live in Westport or elsewhere in Buller District. The mine has a life of up to a further 10 years.
In 2014, the site won a Minerals West Coast environment award for research and practice into fast revegetation of disturbed ground, and in 2020, a Straterra and Freeman Minerals Sector Award for native bird conservation in Kahurangi National Park.
This case study focuses on site rehabilitation. In the year to 30 June 2021, Bathurst rehabilitated 29ha to Stage 1 (see below for a description of stages), 24.6ha to Stage 2, and 28.3 ha to Stage 3.