Like Ali said, it depends on the situation and the kind of drinking this person does. Do you have a custody agreement in place with this alcoholic? Mine, though not legally ratified yet, indicates that both mother and father are to abstain from alcohol or drug consumption 12 hours prior to visitation with the child, and of course during said visitation. So far, I think my XAH has kept to it. He was never, however, a raging drunk and he never drove. Eventually, I assessed that he was just a pathetic drunk who drank more in the evenings and then felt sorry for himself. On my lawyer's advice, I scheduled his visitation in the early afternoon, when he's less likely to have started drinking and when he's probably not still hung over from the night before. I haven't administered a breathelizer test to him though it's been suggested to me that I could before each visit and then assess whether or not he's capable of caring for our daughter.
It really sucks but you may have to play booze police to protect your child from this person.