Conservation groups want to know why no federal or provincial charges have been laid over a massive spill from a coal tailings pond in west-central Alberta.
An estimated 670 million litres of waste water spilled into tributaries that feed into the Athabasca River after an earth berm broke at the Obed Mountain mine on Oct. 31, 2013.
The mine was owned at the time by Sherritt International, which has since sold it to Westmoreland Coal Company.
Groups including the Alberta Wilderness Association say Sherritt should be charged under the federal Fisheries Act.
They also say they want both governments to make public what was in the tailings, how the spill has affected the rivers and how it may affect the health of people who live downstream.
Federal officials and staff at the Alberta Energy Regulator were not immediately available for comment.
"The lack of enforcement and charges for a spill of this magnitude calls into question the approval of any mining development in Alberta," Brittany Verbeek, a spokeswoman for the wilderness association, said Wednesday.
Other groups calling for government action include Keepers of the Athabasca Watershed Society, the Aboriginal Alliance of Alberta, MiningWatch Canada, North Saskatchewan RiverKeeper, Central Athabasca Stewardship Society and the Mikisew Cree and Athabasca Chipewyan First Nations.
A fisheries biologist with the group says the effect of 90,000 tonnes of sediment on the creeks that feed into the river remains unclear.
"These tributaries provided important habitat for threatened Athabasca rainbow trout and bull trout," said Carl Hunt.
A few weeks after the spill the Alberta government ordered Sherritt to clean up the mess of clay, mud, shale and coal particles.
Last year an Environment Canada database said the spill contained damaging compounds such as arsenic, mercury, cadmium, lead and manganese.
The pollutants were found to exceed safety levels as far as 40 kilometres downstream of the spill.
At one point last year the province advised downstream communities not to draw water from the river and farmers not to let livestock drink from the river.
Earlier this year some of the groups petitioned the federal auditor general to seek answers regarding the federal government's regulation of coal mine tailings and its response to the Obed mine spill.