I am certainly no expert in this area , but could you switch it over to some type of organic soil such as Eco-earth or peatmoss?
If i am not mistaken those have a lesser risk of impaction.
I'm paranoid about impaction on my reptiles therefore i only use peatmoss ( an organic soil, not an actual moss) and occasionally mix in Eco-earth soil. this way its all biodegradable and i would assume digestible