The plan proposes a complicated set of wells and pumps to control and monitor water levels and chemistry. But its centrepiece is a wall, nearly 14 kilometres long and between 20 and 70 metres deep, which is intended to protect the unmined wetland while the rest is drained and excavated. “It is untested,” said Lorna Harris, an ecologist specializing in peat with the Wildlife Conservation Society, who has worked at universities in Canada and England. “We do not have any certainty that it will work.”