Water had collected in this gap when our team came in, causing the wood to rot at the bottom. We installed our TrenchDrain System. A trench drain is a linear channel with a U-shaped profile that’s covered by a drainage grate. Used to dispose of unwanted water a trench drain is installed flush with the basement floor at the foot of a the exterior stairway that provides access to the basement from a leaky bulkhead or hatchway door. A trench drain is typically connected to either a drainage channel or directly to a sump pump to remove the water that collects at the base of the exterior stairway.