Our garden is near the base of an incline where the subsoil is clay. When there is heavy rain, the lawn becomes sodden and often there is surface water. Currently considering putting in perforated pipe land drains and collecting the water in a large underground tank.

The plan then is to automatically pump out the tank when it is full and here is where I would appreciate some advice.

Should I go for a submersible pump or an above ground pump that will work with a negative head ie a lift of about 4 feet? Alternatively should I put a pump in the pit alongside the tank?

Any advice would be appreciated. Thanks.