Environment Minister very happy with marine dumping of mine waste ramunickel | July 27, 2011 at 8:10 am | Tags: Chinese mining, Environmental damage, Highlands Pacific, Lihir gold mine, Misima, Papua New Guinea, Ramu nickel mine, SAMS, Simber, Submarine Tailings Disposal | Categories: Environmental impact, Mining, Papua New Guinea | URL: http://wp.me/pMvf7-O0
Environment and Conservation Minister Benny Allan has spoken favourably about the disposal of mining tailings onto the ocean floor, reports The National.
Allen told the PNG mining and petroleum environment seminar last Tuesday in Port Moresby that this was an alternative to land-based tailings storage.
The tailings passed down a deep sea pipeline that discharged well below the maximum depth of the marine mixing zone, generally about 100m deep, the conference was told. ?Water below this depth generally remains effectively cut off from the upper waters by the strong temperature and salinity gradients that extend down through the first 100m or so of the water column,? he said.
Allan said any discharge below the maximum depth of the mixing zone would generally be trapped there by the layers of water above it. ?This method of tailings disposal, referred to as deep sea tailings placement (DSTP) offers an alternative option for mines located in coastal and near-coastal regions,? he said.
The Environment and Conservation Department, working with the Minerals Resource Authority, commissioned the Scottish Association of Marine Sciences to conduct comprehensive oceanographic surveys of three DSTP locations in PNG between 2007 and 2009. These studies assessed the environmental risks and impacts that this method of tailings disposal posed.
Allan told the seminar that as a result of these studies, the Scottish Association of Marine Sciences had prepared a comprehensive set of environmental guidelines for DSTP in PNG, inclu ding the recently completed Ramu NiCo nickel/cobalt mine in Madang.
?I would point out that in keeping with the precautionary principle in dealing with environmental risk, my department applies a substantial safety margin to the depth of all operational DSTP outfalls in PNG. ?These are located at depths of between 130m and 150m, well below the mixing zone.?
He said in the case of the Ramu NiCo, the DSTP outfall discharged at a depth of 150m in the Basamuk canyon. ?From there, the tailings continue to flow down the slope of the canyon to its final resting place at approximately 250m deep in the Vitiaz Basin.
?At this depth movement of the tailings into the upper mixed water is considered most unlikely and the tailings will be confined to this area as they slowly decompose over the coming decades,? Allan said.
He said the disposal of tailings, on land or sea, presented challenging problems in PNG where characteristically high rainfall and geologically active surface formations posed particularly high risks for land-based tailings storage. ?The high toxicity of many tailings materials can potentially last for many years and, thus, any land-based storage facility has to remain secure from flooding, over topping from long periods of continuous high rainfall, and from earthquakes and other plate tectonic movement for this length of time. In a high rainfall and geologically active area these risks are heightened and will require the ongoing monitoring and rigorous management long after the mine has closed and the mining company has gone
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