TIMELINE-Enbridge's Northern Gateway oil pipeline proposal

Dec 18 (Reuters) - Here are some key dates in Enbridge Inc's bid to build a 525,000 barrel per day pipeline from the Alberta oil sands hub of Edmonton to Kitimat, British Columbia, on Canada's Pacific Coast. The proposed C$6 billion ($5.61 billion) project has run into fierce opposition from environmentalists and aboriginal groups, and cost estimates have more than doubled since it was first announced. Canada's National Energy Board will release its decision on whether to approve the pi