dust collection and a slab

[gmack5]

The only thing I'd be concerned about with a below-the-floor system is moisture getting into the trough with a concrete floor. In your location, Mobile Alabama, moisture has got to be a consideration for anything below grade (another vote for a wooden floor, above grade).

At the very least, you'd need to consider a dry sump and grade it to direct moisture away from the sensitive areas of your trough.