"EDMONTON -- Geotechnical engineers remained at the Obed Mountain coal mine Sunday trying to determine how one billion litres of murky water leaked from a containment pond into the Athabasca River."
"A barrier gave way on Halloween, allowing liquid containing coal dust, sand and dirt to flow through two creeks into the Athabasca, said Darin Barter, a spokesman for the Alberta Energy Regulator.
'I haven’t seen this happen. Coal mine incidents and pit leak incidents are really rare,' he said. 'I was surprised this could happen.'"