Rotting Sal is a Hominus Machina boss in Divide. He can be found on a hill just southwest of Foxtrot Outpost near -50, 66,-145 close to a destroyed tower. He is required for Divide Targets of Opportunity and is a mission objective in Dissections: Part III.
Actually spawns at -63, -138 at a ruined tower. That's SW of Foxtrot.