Is there any type of soil, sand, rock, gravel, etc. that would be deterrent to chipmunks? I have a network of chipmunk tunnels under my lawn and patio. I recently removed some topsoil while gardening and opened up a good 6 inch diameter tunnel (with smaller access tunnels) immediately next to my patio. I have left it open for a month in hopes that the chipmunks will not want to go through a tunnel with open access from the outside and/or that it would leave them open to predators, but now I want to fill it in. My thought is that if I use something that chipmunks don't like digging through, I might deter them from that area. I have tried plugging chipmunk holes with sand and small rocks in the past with no luck. I've also tried mixing in commercial rodent repellent with dirt with no success. Is there something I could fill this hole with that the chipmunks not simply dig through once again?