Impact of Olympic Dam/Roxby Downs
The Olympic Dam/Roxby Downs mine has a voracious appetite for water to process the uranium, copper, gold and silver it extracts from underground. It obtains this water from the Great Artesian Basin (GAB) within the Lake Eyre region via two principal borefields, known as Borefield A and Borefield B (sometimes called “Wellfield”). These borefields have been gradually increasing the quantity of water extracted from 1.3 to 15 million litres per day since 1982.
Borefield A consists of a total of 9 production bores in three main locations, and a total of 19 observation bores. Between 1982 and 1987 six of these production bores were flowing under artesian pressure. In 1987 pumps were installed to make up for the loss of artesian pressure, due to drawdown in the GAB aquifer. The final 3 production bores were constructed in 1991 on the southern shores of Lake Eyre South, within the boundaries of Lake Eyre National Park.
Borefield A is located directly within the Lake Eyre and Hermit Hill Mound Spring complexes. Since its opening in 1982, impacts on springs have been evident and have continued to increase in severity as the extraction rate continued its inevitable rise. To date, many springs have declining flows and some springs, such as Venables and Beatrice, have ceased flowing altogether. Venables is now maintained artificially by a pumping station, a unit which is solar powered! Attempts to restore the flow at Beatrice through groundwater re-injection adjacent to the spring have so far been unsuccessful.
There is now a long term decline in artesian pressures in this region which will affect the long term viability of the springs while Borefield A is still operating. One must question the economic and environmental wisdom of a company capable of siting such a borefield right in the midst of such precious springs.
With the long term supply of water still planned to increase further, a new borefield was needed, and the impacts on the springs led to Borefield B being constructed further into the GAB. With the commissioning of Borefield B in November 1996, extraction from Borefield A was reduced to 5 – 6 million litres per day to try and minimise future impacts on the springs. However, the long term impacts on the springs still remain of the utmost significance.
Borefield B is located 100 km north-east of Borefield A between Lake Eyre North and Lake Eyre South. This area of the GAB offers higher yields of groundwater and is distant from many of the mound springs. It consists of 3 primary production bores, each expected to deliver approximately 11 million litres per day under artesian pressure. At present only one bore is connected to the pipeline, having commenced operation in November 1996. It delivers about 9 – 10 million litres per day.
The primary impacts from this borefield were expected to be on pastoral bores located nearby. Computer modelling predicted that impacts would be manageable initially and that it would take a number of years for loss of artesian pressure to become evident. However, reports from people of the region have suggested that loss of artesian pressure is already significantly worse than that predicted.
Olympic Dam Expansion:
Sustainable Supply of Water ?
With the current expansion and proposed expansion of the Olympic Dam mine, the sustainable long term supply of water has been identified as one of the key environmental issues concerning the operation of the mine. The current Environmental Impact Statement (EIS) for the proposed expansion states that the long term supply would need to be 42 million litres per day. However, based on projected water usage rates per tonne of ore processed, the demand for water would be somewhere between 58 – 75 million litres per day. This is a very significant discrepancy.
Clearly, the supply of water from the GAB is not sustainable for the long term life of the mine. Added onto this, the EIS still predicts that with Borefield B at full capacity and Borefield A operating at reduced capacity, many of the most important spring groups will still have reductions of flow, some as high as 100% on current flow rates, not pre-borefield flow rates. Therefore one must seriously question the EIS’s assertion that future impacts on springs will not be significant.
It is imperative that Borefield A be closed permanently, and a new borefield, Borefield C, be investigated and constructed further into the GAB where even higher yields of groundwater are possible. However, it should be pointed out that the only truly sustainable solution is to close the mine.