Treated

For the deck project, I am using Wolmanized Lumber treated to reach 0.15 pcf of CA-C, which is rated for ground contact. Type C copper azole, denoted as CA-C, has been introduced under the Wolmanized brand. The AWPA standard retention for CA-C is 0.06 lb/ft3 for above ground applications and 0.15 lb/ft3 for ground contact applications.
The lumber is punctured and the chemical applied under pressure to push it into the wood. However the treatment only penetrates about one quarter inch into the lumber, so whenever you cut a piece to length, you are exposing an untreated core of lumber. So you have to apply an end cut preservative that is compatible with the type of treatment your lumber has had. (ACQ, CA-C, etc)