You failed a random U/A. That would be a technical violation.
Alcohol is legal for an adult to drink, but it is forbidden to those on probation. In my experiece, however, while one breathalyzer failure will not please your probation officer, it is highly unlikely that he will revoke your probation and demand that the judge resentence you to jail or prison on the basis of one positive.
You did not, at least, drink and drive and/or get yourself rearrested, and that's something in your favor. In general, probation will not revoke probation altogether for a first failure, but they can.
Probation has a whole arsenal of possible sanctions available to them, ranging from a wrist slap (more intensive supervision, more reporting requirements,more random alcohol testing ) on the one extreme to house arrest or revoking probation outright on the other.
What they will do in your case will depend on many factors, such as the defendant's background and history and the facts and circumstances of the underlying case, how well you've been getting along with your probation officer, whether you've been in good over all compliance with the terms of your probation before the violation or whether you've given them trouble before (and how much of it). These aren't all of the measuring sticks that will help probation to decide how to handle you, but you get the picture.
It will all come down to whether probation thinks that working with you will ultimately turn you into a successful probationer and a productive citizen or whether they think you never will get the message and will want to wash their hands of you. It sounds like you've been doing well on probation and I doubt you'll end up facing any jail time for this one violation.
But you'll be entitled to a hearing on your violation. You should notify your lawyer so that if probation and the DA are asking for for a revocation of probation and a resentencing, someone can make a good argument for house arrest. But in my experience, one positive U/A will not cause probation to revoke you or ask for jail.