Short of removing all food for these plant-eating animals, there's really not a way to "get rid" of voles. We are hearing from multiple regions of Oregon that the recent cyclic vole population crashes (2022 into 2023) have apparently ended, and that we're likely back into population rebound phases of their cycles. You don't mention the use(s) of the part of your property being most-impacted. Is this pasture, lawn, or some specific agricultural crop that's taking the brunt? Asking because restricted-use rodenticide (ZincPhosphide, primarily) is only available for some applications (primarily production agriculture) and is only available to licensed applicators and/but smaller scale (e.g., yard) situations can be addressed with snap-trapping and pasture could potentially - depending on how much precip you've had thus far - be addressed yet this year with some plowing to disrupt burrows, etc. Happy to think together on this further if you can help me understand the setting a bit more. Also, if you have photos of the runs/holes, that would help me make sure I'm addressing the correct critter's ecology.