<Tr> <Td> 1999 </Td> <Td> 100,000,000 gal (est) </Td> <Td> Process water containing arsenic </Td> <Td> Unknown </Td> </Tr> <Tr> <Td> 1998 </Td> <Td> unknown </Td> <Td> Acid rock drainage </Td> <Td> Clogged pipe </Td> </Tr> <Tr> <Td> 1997 </Td> <Td> unknown </Td> <Td> Copper sulphate </Td> <Td> Clogged outlet valve </Td> </Tr> <Tr> <Td> 1997 </Td> <Td> unknown </Td> <Td> Process water with pH 2.5 - 4.0 </Td> <Td> Ruptured pipeline </Td> </Tr>

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