1 For gophers and moles dig a trench 2-3 feet deep and install the wire at a ninety-degree bend to the outside (making an L shape), with an above ground portion of at least 6 inches. 2  A wire mesh fence at least 12 inches above the ground and extending 6-10 inches below the soil surface will exclude voles from the area. Create a vertical barrier. 2  For gophers and moles dig a trench 2-3 feet deep and install the wire at a ninety-degree bend to the outside (making an L shape), with an above ground portion of at least 6 inches.