Plumbing rough in under monolithic slab help

[probuilderwalnutcreek]

Building an ADU. The shower drain is straight forward, 2'11" to footings. But there is an outside storage door so I do not know where to rought the vent. I am using a tub box and 2" drain pipe through slab out to main

 

[probuilderwalnutcreek]

I was going to run a 2" ABS drain pipe from the tub box under slab through footing - about 3 feet. But where should I vent?