Over the years in shoring design, it has been common practice to use 3x12 wood lagging in conjunction with steel soldier beams for excavation shoring. This lagging has always carried the specification of "..pressure treated with a minimum retention of preservative of 0.4 pcf approved for ground contact", which follows the AWPA guidelines. Whether used as backwall formwork or not, this lagging is typically left buried. Recently, some clients have objected to this. Does anyone out there have any adverse experience with this practice, or can cite any studies on the matter?
I would be curious to know the answer to this as well. We are currently installing wood lagging that the Owner wishes to have removed at the end of the project. Our previous procedures have been to remove the top three or four feet in case there were future utilies installed.