Far more sewage has been spilled in Canadian urban centres over the last six years than any other harmful contaminant, newly released figures show.
An analysis by The Canadian Press reveals hundreds of millions of litres of sewage, as well as many other dangerous liquids, have been dumped right under Canadians' noses.
This never-before-released information has been kept in a classified government database called NEMISIS. The acronym stands for National Enforcement Management Information System and Intelligence System.
Federal enforcement officers use the database to go after polluters.
It took The Canadian Press two years and a complaint to the information commissioner to pry the data from Environment Canada under the Access to Information Act.
The news agency then created its own spills database using the government information, which covers the period from January 2004 to this past April.
The analysis looked at spills in 18 cities and metropolitan areas across 10 provinces.
They include the metropolitan areas of Toronto, Vancouver and Montreal, and the cities of Calgary, Edmonton, Regina, Saskatoon, Winnipeg, Ottawa, Hamilton, Windsor, Ont., Quebec City, Fredericton, Moncton, N.B., Saint John, N.B., Charlottetown, Halifax and St. John's.
The database lists 6,555 spills in those parts of the country since 2004. Some spills are minor, while others run over hundreds of millions of litres.
The most frequently spilled contaminants are petroleum products. They account for 3,596 spills, or about 55 per cent of all entries.
The database contains 538 sewage spills. That's eight per cent of all spills in the database. While sewage doesn't appear as often as other contaminants, more of it is spilled each time.
The largest spill was at Calgary's Bonnybrook wastewater treatment plant, which handles much of the city's sewage. The database says a storm and flood led to a 300-million-litre sewage spill on June 17, 2005.
Heavy floods hammered southern Alberta that spring. Edith Phillips of Calgary's regulatory affairs branch said the floodwater overwhelmed the city's sewers and treatment plants. She said the flooding damaged ultra-violet lights used to kill bacteria, so treated wastewater flowed into the Bow River.
Phillips said the sewage had gone through two stages of treatment before it spilled into the river. By that point organic materials and nutrients would have been removed from the wastewater.
"It wasn't raw sewage," she said. "It certainly had been treated to the secondary stage, which is equivalent to what most treatment plants in Canada do."
In Edmonton, an equipment failure at the Gold Bar wastewater treatment plant caused 160 million litres of sewage to be discharged on April 18, 2007. The city did not respond to a request to comment.
Environment Canada said a power outage shut down the Edmonton plant's ultra-violet lights for eight minutes, so 160 million litres of wastewater was only partially treated.
"Otherwise, the effluent was properly treated," the department said.
Meanwhile, the government database cites a 2,191-day sewer leak in Ottawa that discharged 190 million litres of sewage. It shows the spill began Jan. 1, 1998, and wasn't reported until Sept. 10, 2008.
The entry baffled Michel Chevalier, Ottawa's manager of wastewater and drainage operations, who said his figures don't jibe with the federal government's.
"I've had problems in the past with databases from the feds," Chevalier said.
"They're entering the data in a funny way, and it's not necessarily reality, or it leads to conclusions that are false. Like in this case, it looks like it's been flowing for 2,000 days. No. I don't know where they get that 2,000 days."
He said city records show 190 million litres of sewage was spilled into the Ottawa river over a four-day period in 2004. A faulty sewer gate was to blame.
He cited even larger sewage spills - such as more than a billion litres in 2006, 19 million litres in 2008 and 26.5 million litres last year - which aren't listed in the federal database.
In each case the untreated sewage flowed into the Ottawa River. Chevalier said the city has replaced the faulty gates and significantly cut down on sewage spills.
Little is known about a 116-million-litre sewage spill in Richmond, B.C., on Dec. 20, 2009. The responsible party, reason, cause, source and cleanup time are not given.
The government database cites another 64-million litre sewage spill in the Vancouver area on July 5, 2009, at the Lions Gate wastewater treatment plant.
But Metro Vancouver officials dispute Environment Canada's reporting of the spill in its database. Paul Lam, the municipality's wastewater treatment plant division manager, said the spill was not of sewage but rather treated effluent, or wastewater. He said a ruptured valve in the plant's chlorination system was to blame.
"That resulted in the release of 64 million litres of treated, but unchlorinated, effluent," Lam said. "So that volume of discharge had been treated through the plant."
He added environmental testing found no ill effects from the spill.
Environment Canada said "evidence provided by Metro Vancouver clearly demonstrates that the unchlorinated wastewater effluent discharged from the (wastewater-treatment plant) ... was not acutely lethal" and didn't violate the federal Fisheries Act.
Faulty equipment is also to blame for a 50-million-litre sewage spill from Saskatoon's sewers on July 19, 2008. The city also had a 10-million-litre sewage spill on Sept. 15, 2006, due to a "storm, flood." City officials were not immediately available to comment.
The database also lists spills of other contaminants.
In the past, Environment Canada has defended the NEMISIS database, which is riddled with missing, incomplete and inaccurate entries. In many cases the type and amount of contaminant spilled isn't known. But the department insists it has all the information it needs to track and prosecute polluters.