I have zero concern about ENB's debt. It has been and is dropping as a % on their balance sheet and is lower now than in the past. It was never a problem in years past when it was higher so there is no valid reason to believe it's debt might be a problem today. This is a reasonably conservative company operating a business where its cash flow from operations is quite consistent and reliable, not subject to big swings, just moving steadily higher. The company has raised its dividend every year for more than two decades now and would not be doing so if it had any real concerns over its debt levels. No one seems concerned about Enbridge's debt but you and I'm going to have to side with the professionals on their assessment of this one. 
For more, see: 

http://quicktake.morningstar.com/stocknet/bonds.aspx?symbol=enb