I assume that a vole is about the same type of critter as a mole, an old farmer told me it was fairly easy to get rid of them. All you need is a plug of chewing tobacco and a shovel. You put the chewing tobacco in one of the runs and wait. once the little guy pokes his head out to spit, you bonk him in the noggin with the shovel.
Come to think of it, that old farmer might just have been pulling my leg.
We've had success in the past with moles and the pronged traps (six or so nails with a spring) found at Lowes or any home improvement site. as the yard is probably already destroyed, find a friend with a terrier type dog, they love digging for crawly stuff, but it will trash some of your yard.
