I have three of the cast iron scissor traps that are actually illegal to use in Washington state. I own them for display purposes only. If I were to use them I would tell you that I have successfully killed about a dozen moles to completely eliminate the local population. No more moles in my fields or the neighbors. That is, if I were to have used them since they are not legal.You've got to use all three traps, set them right, and check them often.
These are moles, the guys that are about the size of a man's hand, pointy nose, big hands, and very soft fine fur. They tunnel to cause some damage but mostly push up heaps of soil. This is why they must die.
Go to your local hardware store and buy three of the traps. They are legal to own but not to use. Then think about installing them all at once on an active system. Killing them all will only last until new moles from a distant field move in since the tunnel system remains intact and attractive to new moles. Where I have done major earthwork and destroyed the tunnels, I get no activity. Darn lazy moles like to reuse their dead buddy's tunnels.