Apologies for being slightly off topic but this maybe of some interest.
I have just completed modifications to my sunken garden shed to avoid the problem of a continuously rising water table threatening the integrity of the storage of my rolling stock.
My rolling stock is stored in a standard wooden garden shed which is located about 4 feet below ground level within a retaining wall of solid breeze blocks on a 6 inch concrete base. Originally I bored a plug hole in the concrete base to allow residual water to drain naturally but after about 3 years the water table would sometimes rise about 1 foot up into the shed threatening the structure and contents.
The best solution seemed to be to block the plug hole and install an automated bilge pump from a yacht underneath the shed. The only slightly tricky issue is balancing the size of the sump that the pump sits in with the pump detector level and the backflow after the pump stops as this can easily end up with the pump "cycling" continuously.
I guess the pictures are self explanatory.