The game was scoreless until the 58th minute when Sanvezzo collected a loose ball off a Salt Lake defensive miscue and fired a left-footed shot across goal and just inside the far post.
The Whitecaps doubled their advantage 6 minutes later. On the play, Darren Mattocks and Sanvezzo worked the ball in from the left corner and Richards finished by curling a shot around a defender and into the net.
Vancouver (10-7-7) improved to 37 points and retained fourth place in the Western Conference with the win.
Nat Borchers scored a late goal for Salt Lake (13-9-3), which blew a chance to grab the top spot in the West.