MOD 6 - Tailings Storage Facility Water Management

As down stream water users and farmers running a business we object to 127 million litres of tailings being pumped into the underground mine void based on the following reasons:
1. The Aurelia Metals, Dargues Gold Mine have a poor track record with numerous sediment breaches from the tailings dam in the past. Sediment laden tailings were released into our water ways and in two of those instances registered downstream users were not notified of the breach until it was too late and water sources were polluted. The mines location at the head of the steep escarpment above the Araluen valley and the plan to pump the tailings underground has the potential to cause serious damage to the environment. Being situated at the top of a major water catchment the water that flows over the escarpment and through the valley is the lifeblood of the community below and further south an extraction point on the Deua River that provides water for the Eurobodalla Shire with thousands of residents. And more immediately the Majors Creek community due to its close proximity to the site.
2. Poor management of the TSF, numerous sediment breaches and issues of noncompliance has led to this absurd proposal that gives us a sense of dread for future implications ( and that of many others) if the Mod 6 were to be approved. The current procedure of irrigating the tailings onto paddocks in a bid to lower TSF levels is unsustainable and logically thinking would lead us to believe that chemical residue through evaporation must be occurring in those areas.
3. Pumping extreme volumes of tailings into the void has the potential to physically destabilize the mines raw walls. The mines location is in fractured granite on a fault line and any seepage will potentially have major long term environmental and humanitarian consequences. There is no guarantee that no seepage will occur and therefore we believe this to be a high risk activity and have serious concerns for long term water quality and community health.
4. The 275 page Mod 6 application is based on scenarios and simulations rather than fact and in researching this subject the planned Mod 6 is a very unusual and dangerous option and as long term residents who care about the environment we don’t want to be part of Aurelia Dargues Mine Mod 6 experiment. Community consultation concerning this proposal was minimal and we were left bewildered after the process and daunted by the 275 pages we were expected to navigate.
5. By the time the negative effects of pumping tailings underground are realised, Aurelia will have sold off the property and left a lasting legacy of contamination to this community.
6. Aurelia plan to treat chemical laden tailings, with other chemicals then to pump it underground is just not an acceptable option, its like moving one problem to a different location that will be out of sight, out of mind. There is too much at stake for the community if the Mod 6 was approved. Triggering social, economically and environmentally negative impacts. Find another solution Aurelia.
7. We question the no mention of remediation funds is described in the Mod 6 documents. Does Aurelia have an insurance policy that is adequate in the event of a major seepage breach of contaminated tailings when pumped into mineshaft?
Common sense must prevail to safe guard our waterways and groundwater catchments to prevent any further contamination from the Dargues Reef goldmine.

The application focuses on the proposal to transfer 110ML of water from the TSF, but also seeks flexibility to transfer at the 10th and 90th percentile. However no detail is provided about what volume of water this would actually constitute. This is unclear for example when reading the information provided in section 9 and section 6.4.3 of the application. If it is not made explicit in the application or potential future approval what the approved value of the 90th percentile is, then monitoring and compliance of transfer against this approved amount will be questionable.

References throughout the application to transferring 110ML of water from the TSF to the mine void is misleading about what the actual maximum amount of water transferred may be (after additional rainfall). The best approximation I could derive from the information provided of total volume after 90th percentile of rainfall - is that this may permit a total transfer of up to 312ML. If I have calculated this correctly, this would exceed the capacity of layer 9 of the mine void (approx. 300ML).

I asked the company whether modelling was conducted of 312ML water transfer, or only of 110ML? The answer they provided from the water modellers was : "The answer to the question is not as straightforward as focusing on one number in the assessment. The modelling assumptions considered a 110 ML transfer from TSF. The total predicted volume into the underground includes a number of inputs. For the 90th percentile result this includes the 110ML from the TSF but also water volumes generated from the rainfall falling on the site catchment, including the pit top storages which ultimately overflow to the underground portal.
Therefore the 90th percentile is an extreme scenario, whereby water from the TSF is being pumped underground and on-site storages are filled with rainfall (ie the capacity of the water management system on site is being exceeded).
The assessment shows the model outputs for the 90th percentile and doesn’t take into account that there would be human intervention in these circumstances to manage water underground and at the surface. There is a detailed Water Management Plan in operation for the site with TARPs set up to deal with extreme events."

Notwithstanding that the company should know the maximum amount of water they are applying for possible transfer (with flexibility at the 90th percentile) - The application and assessment consideration needs to be explicit about what is the maximum volume of water (ie. at the 90th percentile) that this modification seeks and may be provided for. This leads subsequently to monitoring and compliance against this maximum amount.

If the groundwater modelling only considered 110ML water transfer, this does not account for additional time needed to transfer to the 90% of rainfall; and whether this total volume may exceed the void available at level 9 of the mine (approx 300ML). During this time there will also be additional inflow from the surrounding rock substrate into the mine void (the rate of inflow used in groundwater assessment and modelling is not clear from the documentation). Data and scatter plots should therefore be provided for the modelled rate of flow for tracer concentrates at level 8 of the mine with the larger water volume as well.



Submission application Dargues Mine Majors CreekNo. MP10_0054-Mod-6

Subject to whatever is done in the Modification 6 we would support it
providing the Modification 6 is safe for all residents, structures of the interior of the Dargues mine underground is sufficient not to collapse outwardly and impact the ground water, creeks, rivers and Ocean and that this would be guaranteed in any event not to happen by the State Government of New South Wales.

Yours Sincerely
Jeffrey and Irene Wolford

Residents
Majors Creek
NSW

The following are about what can cause problems in mining and concrete.

Source: Australian Town and Country Journal, 29 January 1870, p. 13.
Early mining at Dargue’s Reef and problems with the ‘mundic’
By June 1871, when a correspondent from the Town and Country Journal inspected Dargue’s Reef, there were 20 men working the mine, along with seven to eight horse carts, each transporting ten loads a day to the crushing plant. Two shafts had been sunk to 30 feet on either side of the reef to test it at depth and a small tunnel commenced at the western end of the lode.

Mundic once[2] only referred to pyrite,[3] but its meaning has since broadened to include deterioration of concrete that is caused by oxidisation of pyrites within the aggregate (usually originating from mine waste). The action of water and oxygen on pyrite forms sulphate (a salt of sulphuric acid), thereby depleting the pyrite, causing loss of adhesion and physical expansion.
Mundic block problem
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The Cornish word mundic is now used to describe a cause of deterioration in concrete due to the decomposition of mineral constituents within the aggregate. A typical source of such aggregates is metalliferousmine waste.