These permits allow the water collected in Skyrocket Lake to be discharged into Littlejohns Creek only during heavy winter flows (running at about 130,000 gallons per minute). Procedures control the discharge so the waters blend at a rate that assures there is no change in creek water quality, or any potential influence on downstream flooding or erosion. The discharge maintains Skyrocket Lake at a prescribed level, while allowing Skyrocket to be the collection point for the water from the rock piles. Discharges will be piped through a series of valves housed in concrete vaults, managed by a sophisticated computerized system linked to creek flow and weather conditions. The permits require years of monitoring and water testing to assure the procedures work as planned.
A similar approach appears to have backfired in Queensland, Australia. See the report at this link which reads in part:
The flooding rain from ex-cyclone Oswald has created a major problem for Queensland’s mining industry. There’ve been record falls across much of central Queensland and around 20 mines are discharging water into local rivers with the permission of the Queensland government. According to the Resources Council, those releases will probably negate the most recent rainfall, but won’t reduce the legacy water. Going into this summer’s wet season, it was estimated there was the equivalent of half Sydney Harbour’s worth of so-called legacy water, which has accumulated in mine pits, especially in the northern Bowen Basin region, since 2008. There’s also an uncontrolled release of water from one of the most toxic disused mines in Queensland—Mount Morgan. The former gold mine, 40km south of Rockhampton, is situated on the Dee River. It closed in 1981 and is being managed by the Queensland government. Michael McCabe, the coordinator of the Capricorn Conservation Council says it contains highly acidic water. About 700 mm of rain has fallen over the Mount Morgan mine site since last Wednesday. As a result, the water level in the mine’s open cut pit has been overflowing since Saturday morning, at a rate of about 60 megalitres a day. The state government says strong natural flows in the Dee River have achieved significant dilution of untreated water entering the river, minimising potential downstream impacts. But Mr McCabe says it highlights an ongoing problem.
Not everybody is so optimistic. Local farmers are noticing strange things, as per this report:
The abandoned Mount Morgan gold mine, which overflowed for the first time in its history three weeks ago, is still spilling acid and heavy metals into the Dee River. Local farmers now say that the Dee River is an unnatural shade of blue-green for a lot of its length, and birds and fish are dying. Neal Johansen, who lives near Mount Morgan, says that although waste water has been trickling out of the old mine for years, the damage caused by Oswald dumping 700 mm of rain in the area has been catastrophic. He’s been surveying the river to assess the damage. ‘I’ve never before seen the white sediment on the bottom, which is probably aluminium hydroxide that’s now dropped out because it’s increased to a pH level where it will actually fall out of suspension,’ Mr Johansen says. ‘I certainly have never seen this before. So that is actually of quite a huge concern I should imagine… 55 km downstream [from the mine].’ A little further downstream from where Mr Johansen has found evidence of low pH levels, farmer Ian Scott has now found dead birds.
At this link is a little more on the history of the mine and current attitudes:
In the past decade, some works have been undertaken to try and reduce the pollution, such as seepage interception from leaking waste rock dumps and a water treatment plant to treat the highly acidic water which had accumulated in the former open cut – just a mere ten billion litres or so … (ie. 10 GL or 10 million cubic metres). Although these works have helped to partially reduce the pollution burdens from the former Mount Morgan mine to the Dee River, the pollution burden remains intense and there is a long way to go to restore the Dee River to normal health. The Mount Morgan mine is a ‘classic’ legacy site – generating enormous wealth in its heyday but leaving an environmental disaster which will cost current taxpayers hundreds of millions of dollars.
This story highlights the issue of control of water at mines and, in particular, abandoned or so-called closed mines. It also highlights the issue of the liabilities imposed on taxpayers by the inadequate closure of mines. In Canada we have the Giant and the Faro mines, also major long-term water control issues and significant costs for taxpayers. I was told the other day that a request for proposals is out for yet another consultant to come in to manage cleanup at the Giant Mine (I cannot find any links to this, although I am told the proposals are being prepared.)
There is no ready, one-size-fits-all solution to the problems of these massive, old mines now needing millions to manage and/or remediate. But maybe the approach implemented at the Royal Mountain King mine deserves further consideration.