What tool do I need in order to bore drainage holes in a poured concrete retaining wall? -Mike
A heavy duty hammer drill or rotary hammer with a high quality masonry bit is the tool of choice for drilling into concrete.
The hammer action on the drill propels the bit through the concrete and breaks up any aggregate imbedded in it. This allows you to drill much faster without wearing out either the operator or the bit.
Good luck with your project,