The Scotland prop plunged over either side of a Sean Maitland score while second-half Niko Matawalu and DTH van der Merwe tries sealed a 35-17 victory for the hosts.
The visitors were better after the interval with Cai Griffiths and Sam Lewis touching down, but it was the Warriors who went marching into the post-season, and head coach Townsend insists his troops stand a good chance of prevailing.
"Any of the teams in the last four have a chance," he said. "I would believe we are going to have an away semi-final, but if it's home or away we'll be playing tough opponents, we've played them this season and we know what we have to do to win those games.
"I'm delighted and very proud of the team, we were up against a very good side and the stakes were high.
"If we would have lost we would have been under a lot of pressure. They are the best defensive team in the league so for the players to create and take those try-scoring opportunities shows how much we've progressed.
"We take the initiative, we have a positive mindset in attack and defence, you need balance in the game, but first and foremost you need to be strong defensively.
"Attacking wise not all of it comes off, but when it does it's very hard to defend against."
One sour note for Townsend was the potentially serious knee injury sustained by fly-half Duncan Weir
"We don't know about Duncan," added Townsend. "It looked like a serious injury, he's in hospital and we'll find out, fingers crossed it's not too serious."
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