On average, there is an oil spill in Alberta every two and a half days.

There have been 155 crude oil spills so far this year, according data from the Alberta Energy Regulator.

The majority of the oil spills were caused by a leak by pipelines, which transport 97 percent of Canada’s crude oil and natural gas on land.

Pipelines carry about 200 Olympic sized swimming pools worth of crude oil everyday, according to the Canadian Energy Pipeline Association. These three million barrels of oil travel across Canada and into the United States.

Penn West Petroleum Ltd. reported more oil spills than other companies that operate in Alberta.

The Calgary-based oil producer was responsible for 20 incidents in 2014 so far. Canadian Natural Resources Limited and Cenovus Energy caused the second and third most spills, with 17 and 11 incidents respectively.

A CNRL pipeline was also responsible for the biggest oil spill of the year when 60,000 litres of crude oil leaked near Red Earth on Nov. 14. It is believed a mechanical problem caused the leak, which is the same volume as one of the smaller exhibits of the Toronto aquarium, according to the incident report.

All oil companies are required to report any incidents where oil or a production was by-product was spilt to the Alberta Energy Regulator, the industry watchdog of the province.

The Regulator updates its database every 24 hours, according to spokesperson Carrey Rosa. The database does not include any of the pipelines that cross into other borders or the U.S. because the National Energy Board regulates those pipelines.

“In terms of the common causes of the incidents its corrosion, mechanical failure, and equipment malfunction,” she said.

It’s difficult to say what caused the majority of the spills, because a number of factors can cause a pipeline to leak, she said. The most common causes for pipelines to spill are machine and human error. Farming and construction can often damage pipelines and wells.

“We regularly inspect pipelines in Alberta to ensure that facilities remain in compliance with requirement and if they don’t follow the rules, we have a number of restrictions that we can put in place. We can shut them down for the day, or longer than that until the problems have been fixed,” Rosa said.

The majority of these incidents reported no wildlife or water bodies were affected by the spill.

But Greenpeace advocate Mike Hudema said this information simply isn’t reliable, because oil companies have a vested interest in saying there is no damage to the environment, he said.

The impact of a spill depends on its size and location, he said. Some, like the very serious spill near Little Buffalo in 2011 were disastrous. People complained of nausea and headaches and children had to stay home from school because of noxious fumes, he said.

“What we know is that spills have had a dramatic impact on communities, human health, and of course have had very damaging and long lasting impacts on ecosystems,” he said.

Any amount of oil leaking into the environment can harm the people and ecosystem in the surrounding area, Hudema said.

“There is very little enforcement here in Alberta,” he said. A self-regulation system for the oil sands just doesn’t work. Oil workers often call Greenpeace to tell them about spills that they employers have yet to report, Hudema said.

“Companies have a financial incentive to not report spills. It could mean litigation, it could mean their facility is shut down.”