One side of my pole barn was built on a raised soil base. Over the last 8 years, the soil has slowly been eroding away. I have some pictures but I don't think I can attach them.
Anyway, I am trying to figure out the best option for a retaining wall. I happen to have nine 6"x8"x18' logs left over from our log home construction. I would like to use these since I need to get them out of my garage and they are free

They are not treated so I would need some way to treat them for outdoor exposure to water and dirt. Does anyone know how I could treat these logs to use for the retaining wall? Also, is this even a feasible solution?
I have also considered using treated plywood with veritical support posts.
The wall would only need to be about 2 1/2 feet tall.
Thank you for any help you can provide.