I've got a creek on my property that needs a retaining wall to keep the water from running down hill over the bank and washing away. I'm thinking about using .40CCA treated wood for this retaining wall. How long would the life expectancy be using this against earth on one side and seeing occasional water. This is used as seawall on lakes in my area and that is where I got the idea.

 

I use presure treated stuff on ocasion, it all seems to depend on the individual timber and or the level of treatment. I built a wall in 1984 that still stands and sees road spray and salt spray each time it rains or snows. Now granted this is material that was made a long time ago, before a lot of regulations came out that put a damper on CCA, I am not sure if you can even get treated wood that contains arsenic anymore, seems it is on the nasty list and no longer used. They still sell pressure treateed timbers but with more environmentally friendly material. ( Which by the way, doesn't work as good at protecting the wood ) But I would say if built well including clean draining stone behind the wall you should get 15 years out of it easy.

 

Check with your local power co-op and see what they have in the way of pole cutoffs. They're usually very reasonable and will last much longer than the .40 treated.
FYI, once a power pole is removed from the ground, for any reason, it can't be used for powerline support again.

Shortround out

 

Yep that would be a good idea using the poles. Im not sure how good the new and improved treated is either. A guy i know bought a bandsaw mill and cuts poles into lumber planks ,That would be the way to go if you could find someone that would cut you some. About 20yrs ago my friends dad would soak regular pine lumber in oil and diesel in tubs he made from old barrels welded together those same posts are still up and not rotten. Just a thought.