CALGARY -- Enbridge Inc. is proposing to make up to $500 million worth of changes to the design of the Northern Gateway pipeline system to address safety concerns raised by Aboriginal groups and others.

The pipeline, which already had a $5.5-billion pricetag before Friday's announcement, has been the focus of intense debate among local communities, environmental groups and politicians.

Critics of Northern Gateway -- a paired system of pipelines between the oilsands in northern Alberta and a terminal near Kitimat, B.C. -- have said they're worried about the potential environmental risks it poses within B.C. and in coastal waters.

The Calgary-based company said Friday it had listened to the feedback from public hearings and was prepared to address concerns with a combination of improved technology and monitoring.

"We recognize that there are concerns among aboriginal groups and the public around pipeline safety and integrity," said Janet Holder, an Enbridge executive vice-president.

"With these enhanced measures, we will make what is already a very safe project even safer in order to provide further comfort to people who are concerned about the safety of sensitive habitats in remote areas."

Among other things, Enbridge says its new design would increase the thickness of pipe walls at river crossings. Enbridge says it would also increase the number of inspections it does by at least 50 per cent and staff pumping stations in remote locations around the clock.

"After years of consultation with stakeholders and after personally attending many regulatory hearings for Northern Gateway, it has become clear -- we have to do everything we can to ensure confidence in the project," Holder said.

The Enbridge announcement comes on the same day the Alberta government launched a pipeline safety initiative.

There have been three pipeline leaks in Alberta this year, including the leak of up to 475,000 litres of oil into the Red Deer River, a major drinking water source in central Alberta.

The calls for the review grew louder earlier this month when the U.S. National Transportation Safety Board lambasted Enbridge for its handling of an oil spill in Michigan two years ago.

A report concluded Enbridge bungled its response when millions of litres of oil began to pour in and around the Kalamazoo River in July 2010, comparing the company's handling of the spill to the "Keystone Kops."

Enbridge has promised to apply the lessons from the Michigan spill to its other projects, including Northern Gateway.

The company said it has already made numerous changes and welcomes the opportunity to explain those to the B.C government and the public.

The Michigan spill affected more than 50 kilometres of waterways and wetlands and about 320 people reported symptoms from crude oil exposure.

Enbridge's cleanup costs have exceeded $800 million.