Water Management

Water removed from the mine will be measured, treated and pumped back underground.

Any water usage on site (to fill fire fighting tanks and for dust wash down) will be taken from mains supply (SA Water).

Mine seepage water extracted from the mine will be:

• Within the water usage rights that accompany the property (i.e. no more water will be drawn from the water table than an agricultural landowner would be allowed to draw).

• Water draw will be metered the same as all landowners.

• However, the mine has no use for the water so we will pump the water back into the aquifer.

Mine dewatering and recharge

As the mine will be below the water table level, some water will seep into the tunnels and will need to be pumped out.

The quantities of water recovered will be filtered and pumped back into the aquifer through five recharge bores adjacent to the mine and/or supplied to neighbouring properties.

Managed Aquifer Recharge (MAR)

Australia has become a global leader in Managed Aquifer Recharge (MAR) development, principally on the improvements and efficiency associated with irrigation and management of waterways. MAR is a proven technology utilised in more than 50 locations in urban South Australia.

MAR is used in mining to manage water from dewatering and to ameliorate environmental impacts of dewatering. Terramin operated a MAR scheme at  the Angas Zinc mine near Strathalbyn.

The modelling for the Bird in Hand Gold Project indicates some groundwater will enter the underground workings. Terramin recognise that Managed Aquifer Recharge (MAR) is key to optimising the groundwater management system  and ensuring the protection of groundwater users and the environment in the Inverbrackie sub-catchment 

Managed Aquifer Recharge trials

Terramin conducted a MAR trial during the 1st quarter of 2019, under the oversight of the Environment Protection Authority (EPA ) and the Department  for Environment and Water (DEW). The $1.1M trial was designed to investigate the water management system associated with the proposed reopening of the Bird in Hand Gold Mine at Woodside.

Based on groundwater modelling, Terramin expect the peak re-injection requirement will be on average of 5 litres per second during the fourth year of mining. In the first year of operations, it would average 2.2 litres per second. During the trial the maximum reinjection achieved at one bore was 13 litres per second. The Bird in Hand Mining Lease Proposal assumes up to 8 sites to provide redundant capacity and will create a curtain effect around the operation.

Terramin in association with technical advisors and the community have undertaken extensive preparatory work as part of the development of the mining lease application. The recent trial has further demonstrated the ground water modelling, developed in the prior 5 years, is fit for purpose and further confirms the site’s amenability to MAR as a water management solution.

The Bird in Hand Gold Project will also apply several mine design measures to limit or prevent groundwater level reduction as well as maintain groundwater quality, as a result of mining activities. These measures include;

• Limiting water extraction to the water license assigned to our property (metered)

• Mapping of water bearing zones and ongoing refinement of the geological model

• Design mine plan to avoid known water bearing zones 

• Probe drilling to assess ground conditions ahead of excavation 

• Pre excavation grouting 

• Sharing water with neighbouring properties

• Treatment and reinjection of mine inflows into the surrounding Aquifer through Managed Aquifer Recharge

All the proposed mitigation methods are used worldwide and well proven techniques throughout the mining and civil industries in the management of groundwater.