Draft Letter to the Editor, ‘Yorke Peninsula Country Times’: proposed Hillside Mine near Pine Point, Yorke Peninsula, South Australia

I’ve been following with interest the proposed development of the Hillside Mine by Rex Minerals, as well as both the concerns and support from within the community. Nick Perry’s articles and the accompany Letters to the Editor in the Tuesday August 12 issue of the ‘Yorke Peninsula Country Times’ cover the range of views. There is no doubt that the State is desperate for investment which generates jobs, and this clearly ‘flavours’ the decision by the Government and the mining regulator to approve the proposed mine on the basis of ‘overall public benefit’.

However, there is another dimension to the proposed mine and this is likely to have a lasting negative impact: the proposed mine pits will not be rehabilitated.

Open-cut mining operations are generally destructive of land by their very nature. Open-cut, base-metal mining operations are additionally problematic in having the potential to generate and ‘leak’ acid and toxic metals, like copper.

‘Enlightened’ mining companies wanting a lasting positive interaction with the communities in which they operate work their mine plan so that they can strategically place metallic and acid-producing wastes at depth in the pit (effectively a geological containment) and backfill with benign waste rock and soil. Thus, the landscape has a chance to ‘recover’ somewhat and gradually return to something like a pre-mining condition in the long term.

Much of the land on and around the proposed mine, as in other parts of Yorke Peninsula, has been farmed by some families for up to 140 years. Hillside might operate for a decade and a half. So the community gets stuck, for the long term, with an open pit that will eventually part-fill with water and is likely to be contaminated by base metals. The land will affectively have little or no value. It is likely to require ongoing monitoring to ensure that contamination does not leak offsite and also regular intervention from both the safety and environmental perspectives.

Mining companies effectively ‘borrow’ lands from communities to advance their business, pay their taxes, make returns to shareholders, and hopefully inject money and jobs into local regions. I think that they also have an ethical obligation to return the lands that they’ve effectively ‘borrowed’ (albeit some companies may purchase property for the life of the operation) in good condition so that there is some long-term value to the community. At the outset, mining companies clearly register community concerns about rehabilitation and contamination through statutory community consultation programs. Consequently, they have the opportunity to research and develop mining strategies and plans that give them the best opportunity to rehabilitate the landscape at the end of mine life. ‘We can’t afford to backfill pits because it would make the proposed mine uneconomic’ is not an appropriate response.   Why should communities be left with this legacy?

Mining regulators must make it very clear well ahead of project initiation that they may permit mining operations that potentially leave the community (and the State) with the costs for maintaining the long-term legacies of open-cut, base-metal mining operations. We are now only just seeing the advance of short-term mine operations into productive agricultural areas and towards urban settlements in this State. We’re also seeing the signs of community outrage that must be addressed if all are to benefit from State development projects such as mining.

A Lesson Learned

Field observations

As part of ongoing studies of the nature and distribution of Permian glacigene sediments on Fleurieu Peninsula, we were shown to a location just below the plateau surface near Spring Mount, west of ‘Minnawarra’ Homestead (Fig. 1).  Here, on a north-facing spur high in the landscape, adjacent to scattered outcrops of extensively weathered and ferruginised bedrock, there was a surface scatter of rounded cobbles and pebbles cascading down towards a small dam in the valley. We would normally be looking for just this type of geological occurrence as evidence for Permian glacigene sediments from which the cobbles and pebbles (erratics, outwash gravels) would have been eroded. This site was somewhat removed from the usual locations of Permian sediments that are common nearby at lower elevations in the Inman Valley to the south, and in the Hindmarsh Tiers and Myponga valleys to the north. Nevertheless, the scatter of rounded clasts was distinctive.

Figure 1:  Location map.  Site studied marked by red star.

Figure 1: Location map. Site studied marked by red star.

On closer examination, the clasts were commonly of quartzite and fine-grained gneissic rocks but we could not identify any granite cobbles: boulders and cobbles of Encounter Bay Granites are very common in the Permian deposits along the northern margins of the Inman valley, for example. In addition, many of the cobbles and pebbles here were somewhat oblate in shape.

We traced the scatter of clasts downhill towards a small dam. On the eastern side of the dam a shallow cutting had been made in the hillslope to provide vehicular access to the dam.

Figure 2:  Pebbles and cobbles eroding from a bleached and weathered sand-silt material exposed at the base of a Xanthorrhea.

Figure 2: Pebbles and cobbles eroding from a bleached and weathered sand-silt material exposed at the base of a Xanthorrhea.

Figure 3:  Scatter of pebbles and cobbles eroding from a bleached, weathered and somewhat ferruginised sand-silt material.  Note the oblate character of many of the cobbles.

Figure 3: Scatter of pebbles and cobbles eroding from a bleached, weathered and somewhat ferruginised sand-silt material. Note the oblate character of many of the cobbles.

Various exposures en route to the cutting, for example on the downslope side of a Xanthorrhea (grass-tree), revealed cobbles and pebbles weathering from a bleached, weathered and generally poorly consolidated sand-silt matrix (Fig. 2), which is very like the situation we have observed in Permian glacigene deposits.  First observations on approaching the cutting by the dam confirmed these relationships (Fig. 3).  At the cutting, however, the actual field relationships of the clasts and the matrix are more clearly seen and the clasts tend to have a well defined ‘imbricate’ orientation in the host matrix (Fig. 4).  Immediately to the east in the cutting the relationships become clear:  the clasts are actually contained within steeply dipping weathered bedrock.  Their oblate shape and orientation is a function  of deformation of the bedrock and they are aligned parallel to the steeply dipping layering represented by schistosity roughly parallel to bedding (Fig. 5).  The weathering of the bedrock, which is related to its occurrence in close proximity to the deeply weathered pre-Tertiary summit surface of Fleurieu Peninsula, and which is particularly characteristic of the area around Spring Mount, has extensively altered the rock matrix but apparently little affected most of the contained clasts.

Some outcrops in the small tributary immediately to the west of the dam are of weathered and ferruginised schist and gneiss, but there are no rock clasts evident.

Figure 4:  Pebbles and cobbles with a clearly defined ‘imbricate’ habit within the bleached, weathered and somewhat ferruginised sand-silt matrix.  Again note the oblate character of many of the cobbles.

Figure 4: Pebbles and cobbles with a clearly defined ‘imbricate’ habit within the bleached, weathered and somewhat ferruginised sand-silt matrix.

Figure 5:  Pebbles and cobbles, now seen as significantly deformed parallel to the cleavage in steeply dipping bedrock which has been strongly altered by weathering.

Figure 5: Pebbles and cobbles, now seen as significantly deformed parallel to the cleavage in steeply dipping bedrock which has been strongly altered by weathering.

Clearly, the geology is not reflective of Permian glacigene deposits but of weathered and altered bedrock most likely to be the basal Proterozoic conglomerate that unconformably overlies the Barossa Complex basement inlier in this region. Reference to the geological map (Fig. 6) confirms this possibility. The essentially unweathered conglomerate, which is also spectacularly deformed, is well-exposed in the Inman Valley at Grey Spur, just south of the Spring Mount locality. The same formation (assigned to the Aldgate Sandstone; SARIG mapping) is exposed on the coastline at Lady Bay, south of Normanville, but the deformation here has been very intense and the contained cobbles and pebbles are significantly deformed.

Conclusion

The ‘lesson learned’ is that all is not as it initially may seem in field geology, and jumping to conclusions is not recommended. A close examination of field relationships in any locality, together with questioning of initial conclusions and gathering of all available evidence, might actually uncover an interesting story that would otherwise be missed.

Figure 6:  Geological map showing site location (red star) and distribution of basal Proterozoic conglomerate (Nol Aldgate Sandstone). Geology as follows:  Orange-brown (Lb) = basement Barossa Complex; dark brown (NoI, Nds, Nl etc) = Proterozoic; pale brown (Eec, Eeb etc) = Cambrian Kanmantoo Group; blue (CP-j) = Permian glacigene sediments; orange (T) = undifferentiated Tertiary weathered  zone materials; yellow (Q) = undifferentiated Quaternary alluvials.

Figure 6: Geological map showing site location (red star) and distribution of basal Proterozoic conglomerate (Nol Aldgate Sandstone). Geology as follows: Orange-brown (Lb) = basement Barossa Complex; dark brown (NoI, Nds, Nl etc) = Proterozoic; pale brown (Eec, Eeb etc) = Cambrian Kanmantoo Group; blue (CP-j) = Permian glacigene sediments; orange (T) = undifferentiated Tertiary weathered zone materials; yellow (Q) = undifferentiated Quaternary alluvials.

A R Milnes

R P Bourman

Where do these rocks come from?

In the streets and gardens of Poznan in Poland there are often red and pink coloured rocks.

Stone wall with pink & red coloured rocks

Stone wall with pink & red coloured rocks

I asked my grandfather where all the nice rocks came from.  My grandfather, who is a geologist and who knows all about rocks, told me that these rocks came from Norway.  “Norway? … this is very far!”  I asked him “How did they get here?”

He told me that once there was a time when it was very cold and Norway was covered by a giant ice sheet, more than 2 km thick!!!

The ice slid slowly to the south, tore rocks away from the country and carried the rocks with it.  Later the weather became warm again, the ice melted and the rocks were liberated.  In that way the Norwegian rocks settled down in Poland … after a journey of 1000 km over 50000 years!!!

Ice flow from Norway

Ice flow from Norway

 

 

 

Guest author:  Alexia Thiry, 9 years.  Address:  4Hands, nr 4(17) / 2013-11-24 The International School of Poznan Monthly (Poland).  Guest grandfather:  Dr Medard Thiry, Centre des Geosciences, Mines ParisTech, 35 rue St Honore, 77305 Fontainebleau, France.

Rex Minerals’ Hillside Mine – a critique of the proposal

There are components of the Rex Minerals’ Mining Lease Proposal and Management Plan (Hillside Project, east coast of Yorke Peninsula between Ardrossan and Pine Point; http://bit.ly/19jBZFj) dealing with operational environmental management, and closure and rehabilitation of the operation, that are far from ‘best practice’ in the mining industry in this day and age. This is particularly the case with a proposed base metal (including uranium) mining, processing and transport/export operation close to urban infrastructure, existing agricultural landuse and the marine environment.     

Map showing location of proposed Hillside Project in relation to Ardrossan and Pine Point on Yorke Peninsula, South Australia

Map showing location of proposed Hillside Project in relation to Ardrossan and Pine Point on Yorke Peninsula, South Australia

In particular:

1. There is a less than rigorous and transparent approach to describing and managing the uranium content of the targeted ore and its fate in the processing and waste streams. IOCG ores (Olympic Dam, Prominent Hill) always contain uranium. The issue is principally one of radiation protection for the workforce during the operational stage of the operation (especially when mining underground) and the legacy phase following decommissioning and rehabilitation of the contaminated minesite. I’m concerned that there was no mention of mining uranium (even though it is not one of the target metals) in the Referral (EPBC 2012/6434) submitted by Rex in 2012 to the Commonwealth under the Environment Protection and Biodiversity Conservation Act 1999.

2. There is a lack of rigour in the design and management of the TSF, particularly from the viewpoint of adequately engineered and HDPE-lined floor and walls to minimise seepage during operations.

3. The proposal to ‘bury’ the pipelines carrying slurried concentrate and process water between the mine and the port is far from best practice. No experienced mining or energy company will bury pipelines carrying toxic materials because of the inadequacy of leak detection systems (which ideally detect significant leaks) and the inability to make daily inspections along the pipelines to detect small-scale failures and leaks that may be a prelude to significant failure. Examples of companies paying large fines for contaminating the environment as a result of undetected leaks in buried pipelines in Australia (for example, GEMCO’s Groote Eylandt operation – leaking fuel and ERA’s Ranger Mine – leaking tailings pipeline) are well documented.

4. Using the open pit as a final contingency for containing excess leachate from mine landforms and contaminated runoff water and sediment during operations is good practice. However, the lack of a water treatment facility allowing treatment and disposal of pit water may restrict access to the pit (and the underground) following periods when this contingency is required. A water treatment facility would also have considerable value in facilitating mine closure.

5. The proposed rehabilitation strategy is minimal, inadequate in terms of the long-term stability of the post-mining landscape, and espouses the outmoded view that ‘… backfilling the pit and properly rehabilitating the site may sterilise the resource for future operators ….’. To state that the regulator (DMITRE) ‘requires’ this approach is of great concern. It is very unlikely that an operator such as Rex would not fully exploit the existing ore resource and any additional brownfield expansions identified during the mining process. The truth is more likely to be found in the bottom-line economics of the project. By implementing a minimal (and least costly) rehabilitation strategy, the legacy of managing a contaminated base-metal hard-rock minesite such as Hillside, including an open pit part-filled with water of dubious quality, can be passed on to subsequent ‘owners’ and eventually the community and the taxpayer. There are many examples of this dilemma, including former mines at Rum Jungle, Nairne and Mount Todd, where inadequate attention to rehabilitation has left contaminated sites that continue to pollute local and downstream environments.

6. The value of a rehabilitation bond mentioned in the MLP is predicated on approval by the regulator of Rex’s minimal and inadequate rehabilitation strategy. Consequently, in the event that the project becomes uneconomic or for some other reason is curtailed prematurely, there will be significantly less money available than needed to appropriately rehabilitate the mine and port facilities, as well as to manage the post-closure landscape in case there is a legacy of surface erosion, failure of revegetation or contamination of surface and groundwater systems.

7. An appropriate and effective rehabilitation strategy would place all contaminated rock and soil wastes (including tailings and unprocessed ore) back in the pit, which is an effective and stable geological containment structure. The pit would then be backfilled with waste rock and the surface landscape returned, as closely as possible, to the pre-mining condition so that it could be managed in the context of the surrounding landscape and therefore have some value to the local and regional community. There are good examples of this approach (Normandy Woodcutters Ag-Pb-Zn mine near Batchelor and the well-known and widely publicised strategy being implemented by ERA/Rio Tinto at Ranger Mine in the Northern Territory (http://bit.ly/19ggPb4).

8. Pit backfill can be initiated during operations if there is a clear transition from open cut to underground mining. This can be very cost effective in comparison with a post-mining backfill operation, and would minimise costs associated with managing tailings as well as contaminated waste rock and below economic grade ore on the surface. It would require the portal to the proposed underground operation to be located outside the pit or in the highest levels of the pit. This is the approach currently being undertaken at Ranger Mine.

9. The value of the rehabilitation bond should be calculated, based on an independent audit each year, on the full cost of rehabilitating the site (according to a strategy similar to that described above) from the state of the mining, processing and exporting operation each year. This would ensure that the community and the taxpayer are not left with a legacy issue should the operation become uneconomic or for some other reason close prematurely. This circumstance has occurred at many small mines and one current example is the Angus Mine near Strathalbyn, which has been ‘mothballed’ and has an uncertain future.

10. The lack of a water treatment facility and thus a stated reliance on upstream interception, evaporation, and re-injection of ‘surplus’ (waste) water into local groundwater or release into the sea (depending on water quality) is a risky proposition from the perspective of avoidable environmental detriment.

In summary:

Significant effort has gone into the production of the Hillside Mining Lease Proposal and Management Plan as a component of the Pre-Feasibility Study for the Project. The Project is a short-term, large-cost operation and is representative of several new mining proposals in South Australia that are beginning to impinge on modern agricultural (as distinct from outback pastoral) and urban environments. Consequently, local communities and interest groups are rightly demanding a role in the approval process, guarantees that they will benefit from the project, and assurances that the landscape will neither suffer degradation or environmental damage during operations nor be left in a condition after mine closure which has no community value and may require ongoing maintenance.

Unfortunately, much of the plan for the mine described throughout the MLP assumes that there is minimal rehabilitation. That is: (a) the infrastructure will be removed unless there is a downstream benefit to the local community or added value to any subsequent land use by leaving in place storage sheds and associated water and power reticulation. On relinquishment of the site by Rex, the ‘new owner’ will be responsible for any future maintenance and liability; (b) the haul roads will remain in the pit to divert runoff water to the pit lake and these will link to haul roads from the waste rock dumps to form an internal drainage system to divert runoff; (c) the pit and underground will remain as voids filled with water (including contaminated site water), taking more than 500 years to fill to an ‘equilibrium’ level, according to Rex’s modelling, and will be the repository for contaminated sediments and soils as required. Earth bunds will be constructed around the pit to prevent access by light vehicles and will remain ‘in perpetuity’, together with ‘appropriate’ fences and signage, to ‘make it safe’; (d) the waste rock dumps, to be shaped and rehabilitated in-situ, will encapsulate the TSF, any potentially acid-forming waste rock, any ‘uneconomic’ copper ore, and any ‘residual high level radioactive materials’; and (e) the operational water management (drainage) system will be maintained after closure until surface water quality meets the agreed upon water standards for the naturally occurring drainage.

This approach will leave the minesite in a similar condition to many small-scale, short-term, hard-rock base-metal mines throughout the country – that is, areas of major land disturbance and essentially (geomorphically) unstable waste rock landforms that encapsulate environmentally hazardous waste materials from the mining operation, together with pit ‘lakes’ containing contaminated waters. Compared with the pre-mining condition, these areas have no value to the community, but remain places to avoid and, commonly, require major sources of funding from the taxpayer to minimise the ongoing degradation and contain the contamination that can seriously affect downstream environments (note for example, Nairne Pyrite mine, Mount Todd gold mine, Rum Jungle uranium-copper mine). This is unacceptable in this day and age.

Mining companies must take the responsibility to rehabilitate their mining operations in such a way that the post-mining landscape is returned to something approaching the pre-mining condition, which means returning all contaminated wastes to geological encapsulation in the mine pit (or underground), backfilling the pit void to match if possible the former topography, and reconstructing ecosystems (vegetation) that are appropriate and self-sustainable. Under these circumstances, the area should have value to the community (and any future owners) and not represent a shameful and costly environmental legacy.

Dr Tony Milnes (anthony.milnes@adelaide.edu.au)