Michael Walton, Mike Grob, Bret Guetz and Jason Hartwick share third place at minus-4. John Lieber and Rick Gibson are one stroke back at 3-under-par 67 at Royal Colwood Golf Club.
Heffernan played the back nine first with eight pars and a birdie. After a birdie on one, he picked up back-to-back birdies from the fifth to get to 4 under. Those birdies came after a stellar par at No. 4.
He lost his tee shot into the right trees. However, Heffernan hit a stellar second shot through the trees and over water to the green, where he two-putted for par. His final birdie came at the eighth.
'I played really well, just missed one shot all day,' Heffernan stated. 'This is my favorite course in Western Canada. It doesn't get any better than this. Hopefully I can carry it into Friday.'
Tanner got off to a good start with birdies on three of his first five holes from the 10th. He bogeyed 16, but birdied 17 and 18 to turn at minus-four.
After a birdie on one and a bogey at the fourth, Tanner took the outright lead at minus-six with an eagle from off the green at the par-five fifth. However, he fell back into a share of the lead with a bogey on nine, his last.
'That's the best I've played in a long time,' admitted Tanner. 'It's always good to start well. Instead of playing for the cut, you can play for the tournament. I need to be in contention and playing for the win, not playing for a check.'
Jon Turcott, Brad Pemberton, Jesse Smith, Daniel DeLeon, Steve Friesen, Brad Fritsch, Ben Greve, Norm Jarvis and Clint Jensen share ninth place at two- under-par 68.
Defending champion Craig Taylor carded a one-over-par 71 and is tied for 42nd after the opening round.