We have several huge ant mounds surrounding our property. How can we get rid of them?

Buy some Equal or Sweet N low and empty the packets into the mouth of the nest. This is used as ant killer elsewhere in the world with great success. I use Sweet N Low on all my ant piles and within 2 or 3 treatments spaced over a week and a half they have all gone away from the nest. Sometimes though they will travel underground and build new nests about 2' to 4' away from the original nest. Just keep feeding them the Sweet N Low and soon they'll just die off. A couple of boxes of sweet n low will do the trick. Try not to get it wet if possible. Don't use right before a rain storm. And don't eat the stuff as you know it's ant poison - I don't.