What is Vista Gold’s current status with the Mt Todd mine site? Vista Gold is currently managing the site while it works to lay the groundwork for fast-track development of the project – this work includes: working with the regulators to obtain additional authorizations for the mine to reopen, engineering, and ongoing project optimization. As the gold market improves we expect to be well-positioned to make a final investment decision to proceed with the project.
How much has Vista Gold already invested into the site? Vista Gold believes that the Mt Todd project is a world class deposit with continued growth potential, as of the end of 2017 we have invested more than $100 million in advancing the project, $10 million of which has been invested into innovative water treatment and management programs.
We share the opinion with regulators that the most viable path to a long term solution for Mt Todd involves the responsible development of a new mining operation.
When will Vista Gold make a final investment decision? Vista Gold plans to make a final investment decision when the gold price improves and there is sufficient interest in the equity markets to finance the project.
What are some of the environmental issues Vista Gold faces with this site? Collection and storage of mine affected water is the biggest environmental issue facing the Mt Todd site.
Since the mine ceased operations in 2000, mine affected water has been collected in the Tailing Storage facility (RP7) and the Waste Rock Dump Dam (RP1). As required this water has then been pumped and stored in the Batman pit (RP3). In 2013 and again in 2014 the water stored in RP3 was successfully treated to remove over 98% of the metals and raise the pH to an acceptable level just above neutral.
Without the discharge of treated water, there has been a historical 1.5 GL net annual increase in the total volume of water found on the Mt Todd site. Regardless of when the mine goes ahead there is a need to discharge treated water from RP3 every wet season and at the appropriate time there will be a need to treat the water in RP1 and RP7 for subsequent discharge as well.
How has the water on site become affected by the mine? Inadequate closure and rehabilitation by previous operators of the mine site has resulted in significant quantities of waste rock containing sulphide minerals being exposed to meteoric water during the wet season. Sulphide minerals oxidise (rust) which gets washed out of the rock dumps and become what we call mine affected water. The water is broadly known as acid rock drainage (ARD) or acid metalliferrous drainage (AMD) and contains elevated levels of various metal ions and a low pH (effectively a weak acid). Most of the mine affected water on site originates in the waste rock dump, with comparably minor amounts generated by the heap leach and the low-grade stockpile.
How much water does Vista Gold need to release from site? As of the start of the 2016-17 wet season the Mt Todd mine site held an inventory of 9.8 gigalitres of water, 6.6 gigalitres is held in Batman pit. In order for the mine to reopen, all water contained in the pit will eventually need to be removed.
In August 2020 there was less than 3 GL remaining in the Batman Pit
The total amount of water to be released from site however, is subject to rainfall each year.
Vista Gold has released water from site this wet season in accordance with our Waste Discharge License issued by the Northern Territory Government. (All water releases are reported on the Mt Todd website.)
What will you do with the "sludge" at the bottom of the pit? The metals and limestone, which is used in the treatment process, form an emulsion on the bottom of the pit. Before the Batman pit can go back into operation this emulsion needs to be removed. The emulsion from the Batman pit will be pumped to the existing Tailings Dam (RP7) on site. This facility is designed to permanently contain tailings from the ore processing plant and is monitored to ensure the integrity of the Tailings Dam.
What is a Waste Discharge Licence? A Waste Discharge License (WDL) prescribes the conditions for release of water from site pursuant to the Northern Territory Government Water Act. The WDL regulates the discharge of potential contaminates to water in the Northern Territory. Licensing controls the type, quality and quantity of discharge and ensures that monitoring and reporting occur on a regular basis.
Further information regarding a WDL can be obtained from the Northern Territory EPA Website.
What is the long term water management solution? If the Mt Todd Gold Mine is reopened, Vista Gold intends to build an on-site water treatment plant. When in operation the project will consume most of the water as part of the processing for gold.
So what will happen to the Batman pit when you finish mining? The Batman pit will eventually hold storm water and become a permanent source of water for the native wildlife.
How will you prevent the water in the pit in the future from being contaminated? Rehabilitation of the site will ensure that the waste rock is suitably encapsulated, this means that water will not be able to penetrate the dump, thereby eliminating the generation of mine affected waters or ARD which could affect the environment.
The pit walls will have very little exposed ore material, as we will have mined and processed it.
It has been suggested that Vista Gold should refill the Batman pit when it finishes mining at Mt Todd, is this a viable option? The only time when backfilling a mine is a viable option is when you are mining more than one pit and backfill one pit with waste rock from another.
To mine, for say 15 years, and encapsulate 100% of the waste rock that can cause ARD provides a permanent solution.
Backfilling would take another 15 years of mining the waste dump to put it back in the pit, this is not an economically viable option.
But isn’t filling the pit considered “world’s best practice”? Complete backfilling is a common practice in large strip coal mines and partial backfilling has been voluntarily undertaken in small open pit operations with multiple pits. Backfilling large open pits is not considered to be “world’s best practice” for many reasons. Great care is taken in the design and scheduling of the construction of a waste rock dump. Moving material from a waste rock dump back into a large open pit would require years and expose carefully placed and environmentally isolated mineralogical groups to accelerated oxiding conditions and significantly increase the potential for the generation of ARD with the subsequent risk of surface and groundwater contamination. A better view of world’s best practice is to ensure that 100% of the acid generating or potentially acid generating rock is encapsulated and not able to affect the environment.
How much gold will Vista Gold mine from this site? The Preliminary Feasibility Study results announced by Vista in September 2019 include reserves of 5.9 million ounces with expected production of 5.3 million ounces over a life of up to 13 years, depending on the scale of operations.
Ultimately, total gold production will depend on economic factors such as the gold price, foreign exchange rate, cost of energy and consumable supplies; all of which will affect the mine design considerations.
When will mining commence? Vista Gold is yet to make a final investment decision to proceed with the project but when a favourable decision is made, mining could commence following a two-year construction period.
What is the life of the mine? Current plans estimated that the mine will be in production for up to 13 years, depending on the scale of operations.
What opportunities are there for the local community? Our current estimates are that Mt Todd will require a workforce of around 450 people during construction and 350 for the operation of the site.
We would expect that almost all of the workers will live in Katherine or Pine Creek, boosting demand for goods and services from local businesses. Vista will continue to show preference for doing business with local companies and will use the profits from its operations to explore and expand operations if warranted.
Vista Gold is committed to training and developing a local workforce for the life of the mine which is currently estimated at 13 years.
Long term benefits from Mt Todd reopening also include rehabilitation of the site and sound environmental management.
How long is the construction period? We anticipated that construction will take approximately 18 months plus six months of lead time for per-construction of long lead time items. Construction of the power station will commence 12 months prior to commissioning the plant.
Can I fish in the raw water dam? No, due to Vista Gold’s site management policies and commitment to public health and safety, the site is restricted from general public access.
Can I fossick for gold etc on the site? No, due to Vista Gold’s project management policies, its obligations to act as stewards of the land, and its commitment to public health and safety, the site (including the exploration licenses) is restricted from general public access for fossicking or other uses.
Where do I go for more information? The Mt Todd website is regularly updated with project information. We also attend local mining events and the Katherine Show. Major announcements or new developments on the project will also be advertised in the media.