I found this ingenious setup between some townhouses.  Inside the grate is a sump pump.  All of the surrounding yards drain to this pump.  What's in the bag you ask?  It wasn't always in a bag.  Originally it was an electrical outlet that had been run across the ground and laid on top of the grate.  As soon as there was too much water, outlet was submerged and it shut off like it was supposed to.  Problem was that then the sump pump didn't have power and could no longer pump the water out to the street.  The home owner put the outlet in a bag to try and keep it running until a professional landscaper could come and do a proper repair of the drainage.  The home owner went out of town for the weekend and come back to a flooded house, thanks to this less than optimum drainage setup. 

Brodie
Georgia Home Inspector.