Go to your employer and ask to see the DAMP. As an employee / contractor etc with an SSAA you are required to read it. All will be revealed.
A lot of DAMPs (mine included) only calls for pre employment and post incident / accident / reasonable suspicion testing. CASA can do all the random testing they like.
One important thing to remember also is that ALL acohol testing under a DAMP must be by approved breathalyser. Urinalysis is only acceptable for the other goodies.