Cowal's tailing ponds
"The tailings ponds proposed at the Lake Cowal Gold Project cover an area of 350 hectares. At this size, the ponds would be very difficult to manage..." From the Coalition to Protect Lake Cowal.
TAILINGS PONDS (SIZE AND DISCHARGE SYSTEM)
The tailings ponds proposed at the Lake Cowal Gold Project cover an area of 350 hectares. At this size, the ponds would be very difficult to manage. With the construction of the pit and other mining activities that eliminate or disturb habitat, the ponds would offer an attractive habitat to birds and serve as a “safe refuge”. Best practice guidelines suggest that small cells are preferable, not large, for management and for reducing attractiveness to wildlife.
For example, “Best Practice Guidelines: Reducing Impacts of Tailings Storage Facilities on Avian Wildlife in the Northern Territory of Australia” (October 1998, Northern Territory (NT) Department of Mines and Energy) clearly states that design should minimise dimensions of tailings cells.
The large 1.3km by 1.3km surface area of the tailings ponds would hamper effective wildlife management. The Northern Territory (NT) guidelines state that large tailings cells should be avoided as they attract a large number of birds and “make supernatant and tailings difficult to manage”. Furthermore, Smaller operational ponds are recommended where water could more easily be shifted from one pond to the other during an emergency detox situation.
If bird frite ammunition is to be used, it can only reach 75-80 metres at best (Australian Defense Industries). On this matter, NT guidelines state that cell dimensions should be modified “so that a bird frite operator is never greater than 75m from the birds. At the Cowal Gold Project, it would be impossible with such a large surface area to monitor whether small birds such as the 14 cm long Red-Necked Stint have flocked to the middle of the pond where they are resting after their 17,000 kilometre flight from Siberia.
Tailings would be discharged through spigots coming from the pipeline over the walls of the cells. This would push the water to the middle of the pond where the quay is located (pump near quay recycles water back to mill). These features would attract wild fowl and ducks to the middle where they are difficult to scare off if suffering from the effects of cyanosis.
If the cell ponds were smaller, the pooling in the middle would be exponentially smaller as would the distance from the walls to the ponded area. These smaller ponds would be less attractive as habitat to birds and it would be easier to scare birds from the site.
Tailings ponds are known to be a risk to birdlife and other small animals. There are two management options: 1) detoxification and 2) denying access to wildlife.
Discharging peripherally has the greatest risk to wildlife by offering only the former option. In case of a problem, the only available management technique in a peripheral discharge systems is to detox. The second option of denying wildlife access would be unavailable. In case of a problem, the lake would become toxic and untreatable.
A central thickened discharge system is a more effective means of minimising risk to wildlife by discharging to the middle of the ponds and offering less attractive habitat to wildlife. With these sorts of systems, you often don't have free standing water except on the edges, approximately 10 metres wide at most. With such a narrow band of free standing water, animals can be scared away easily and the pooled areas, if any, can be intensively managed as well (In-situ detox is possible because of the small volume of water).
In the case of Lake Cowal, sensitive habitat would be disturbed by the mining activities. The large tailings ponds with peripheral discharge systems would in many ways replicate this critical habitat and provide attractive and dangerous habitat to birdlife.
Smaller ponds with central thickened discharge systems would be far less risky. Even in this scenario, migratory waders might still be attracted to the central discharge. Risks on migratory wader birds would need to be further explored.
From the Coalition to Protect Lake Cowal
(02) 66213294 ~ firstname.lastname@example.org
PO Box 368, Lismore, NSW 2480