Raw sewage from the City of Gatineau overflowed into the Ottawa River on almost 1,500 occasions in 2007, with overflows ranging from a few minutes to a few days at a time, the city reported.

So far this year, the city has dumped sewage into the river more than 500 times.

Like Ottawa's sewage system, which releases more than four million litres of raw sewage into the river each year, Gatineau's is designed to allow raw sewage to overflow into the river after heavy rain. That's because the volume of storm water and sanitary sewer water combined is often too large for the system's capacity, said Louise Lavoie, head of Gatineau's environment department.

"We don't have a choice right now," she told CBC in French, adding that if overflows weren't allowed, the sewage would back up into people's houses.

Unlike Ottawa, Gatineau doesn't keep track of the volume of sewage that ends up in the river, Lavoie said.

In Quebec it's the Ministry of the Environment — not the city — that monitors the quality of the water.

But Lavoie said officials on the Quebec side of the river are aware sewage overflows damage the health of the river, and they want to reduce them.

Gatineau is conducting a study to determine which parts of its sewage system should be improved first, she added. Results are expected early next year.

Nicole Desroches, spokeswoman for the Outaouais Environment and Sustainable Development Council, said action by cities to fix the problem is slow partly because of the Ottawa River's size.

"Because it's a big river," she said, "the attitude has always been dilution is the solution to the pollution.… Probably, if it was a smaller river, I think there would be more action."