I have a urine test scheduled for Monday @ 9am. I usually enjoy a total of three beers a day (36 oz.). Since I drive a Tractor/Trailer rig five nights a week, I need to pass this test. About how many hours prior to the test should I avoid consuming beer?

80 from what you have written as you are a habitual drinker. Be aware there are many other factors to consider. Is this your first test? How have you been passing previous tests?

Please tell us where you drive so we can avoid the road.

Easier not to drink at all. If you can't manage to wait that long you have issues more serious than passing the test or not. And good god....how did you get a CDL? Think about all the innocent people you are putting at risk. Three beers a night every night is a lot of beer.