Client - Xstrata Coal NSW
Task - Open Cut Mine Rehabilitation at Baal Bone Colliery
Value - $1,700,000
Date - 2007 - 2010
Baal Bone Colliery was developed primarily as an underground mine in 1982 on the western edge of the Sydney Basin near Lithgow. However, prior to these efforts by the private sector, the Federal Government operated an open cut mine at the site around 1940 through to 1952. These previously open cut areas were left without rehabilitation and remained as a liability to the current mine owner and the surrounding environment. In 2004 Xstrata devised a plan to win previously unexploited coal resources whilst integrating the old open cut workings as part of the new mine footprint, hence rehabilitating an unwanted inheritance from the past.
Any attempt at achieving true restoration to a previous state appeared daunting and probably impossible given the large scale land disturbance. Therefore a pragmatic approach was needed to kick off essential ecological processes such as biomass production, nutrient cycling, followed by groundcover and erosion control. Accordingly primary objectives included planting of species with a successive tendency to increase soil carbon, fertility and soil structure. A system of soil conservation banks and rock lined waterways was also considered essential in the short to medium term to minimise erosion and, very importantly, sedimentation of downstream waterways. Large scale stream works were also necessary to convey the Ben Bullen catchment discharge through the open cut mine site and to promote a stable stream and riparian environment.
The Soil Conservation Service (SCS) has actively engaged with Xstrata on a cooperative basis to develop solutions acceptable to Xstrata’s commitments under legislation and their own high company standards. The SCS has also implemented these plans under contract to Xstrata.
Works have included:
- Preparation of plans to control runoff from the new open cut landscapes and to promote revegetation
- Works including graded banks, sediment traps and dams and rock lined channels for safe conveyance of runoff from disturbed areas
- Amelioration of soils to reduce dispersion and improve soil structure with gypsum, lime, composted organic materials
- Sowing of areas using aerial and ground methods with native tree, shrub, native grass species and improved pasture species in keeping with the overall post land use plan
- Rock structures to stabilise the Ben Bullen Creek channel in its new form
- Planting of trees in strategic areas to enhance revegetatio; and
- Maintenance sowing and fertilising of areas to promote increasing biomass.
The northern open cut during major reshaping in 2007
The same area in 2009
Northern open cut with graded banks and ground surface prepared for sowing
Establishing pasture areas - 2009
Establishing native vegetation 24 months after sowing in Spring 2009
Maintenance fertilising in subsequent growing seasons
Many difficulties have been encountered on this mine site including a lack of available topsoil, moderately dispersible inorganic clay surface soils and a drastically altered drainage system including the Ben Bullen Creek channel. Despite these limitations approximately 120 hectares of land has been elevated to a stable state with increasing ecological function. Additionally approximately 2.5 km of the Ben Bullen Creek channel has been stabilised. Xstrata continue to monitor the trajectory of the rehabilitated areas via Landscape Function Analysis, an assessment technique for estimating quantitative and qualitative progress towards a self sustaining ecosystem. Another significant outcome for Xstrata is the reduced rehab liability at mine closure or sale.
Community & Environment Coordinator - Baal Bone Colliery
T: 02 6350 6920
Bruce Hundy, Senior Environmental Officer, SCS, Lithgow
T: 0427 259 783