There are several ways I've discovered to get rid of voles. If you want a new lawn, you can use explosives. Nothing else works except zinc phosphide -- and be VERY careful with it, 'cause it IS a poison and you MUST clean up any above-ground bodies you find before other animals get to them.

You can also pump a lot of gasoline down the holes and light it. This will also have some fairly interesting results, the least of which is getting to know the local firefighters and police.

Some suggest setting snap traps crosswise in the vole tunnels, baiting them with peanut butter. You have to cover the hole you made to set the trap, though, or the voles abandon the tunnel.