growing up on a farm,we had many tricks to rid our fields and yard of moles and gophers when traps didnt work.
one of course is the ole bucket of water down the hole until the critter showed up gasping for air and you stomped it to death,or the rat terrier played games with it.
others included: a running lawnmower with a flexpipe down the hole to kill them with carbon monoxide,( may take a bit )
another one was anhydrous ammonia,( very risky ) but worked instantly,only draw back was very green spots in your yard.
if you can still find them,gopher peanuts,they contain cyanide,very quick and permanent also.