How do I get supervised visitation for my daughter’s father?

I think my ex should have his visits with my daughter be supervised. I live in Sacramento and he lives in the Bay area. Because of the distance, he only sees our daughter every other weekend. He is a big drinker and I’m worried that he’s drinking again on the weekends she is with him. She isn’t old enough to know exactly what he’s doing, but she does describe some things that make me think he’s drunk around her. If I don’t think my daughter is safe when she’s with her father, what do I need to do to have his visits be supervised by someone, at least for awhile to determine if he can stay sober when he’s around our child? Because he lives 2 ½ hours from me, it isn’t practical for me to be the one to supervise and I don’t think he’d allow it even if I could.