I have a set of stairs into my basement that lead from an outside bulkhead. The floor under the stairs is dirt, and a source of water into my basement when the water table gets too high.

I would like to cement the floor and create a "tublike" water proofed area, to collect any water into bucket with a sump pump in it and pump any excess water out.

What do I need to put under the cement before I pour it, and what do I use to waterproof the Cement?