Basement Tanking - Project 2

Lift Shaft Drainage

Click on any of the images for a larger view.

ISCA Preservation was contacted about a water ingress situation where the base of a lift shaft was constantly flooding. The shaft was holding approximately 700mm of water, and was pumped out three times a day.

Because the shaft was suffering from hydrostatic water pressure from the water table, and natural spring water, we devised a system that would allow the water to continue to enter the shaft and discharge it by a sump pump with a battery back up system.
In conjunction with engineers and the main contractor, the base of the lift shaft was redesigned. Here the contractor is cutting through the shaft base.

The sump basin excavated with additional steel reinforcement.

The requirement of the lift installers was that there was no drainage pipe work interfering with the floor or wall surfaces. Consequently when the concrete was poured, channels were made to accept the discharge pipe work from the sump pump.

The base of the lift shaft was connected to an additional shaft adjacent to this lift shaft, which was also flooding. We decided that it would be beneficial if both shafts could be drained by the same sump pump system, and so apertures were made to connect the two shafts.

The sump basin with pump installed, with the drainage pipe work exiting through the shaft wall.

Cut outs to allow water to enter the lift shaft from the adjoining chamber.

This system of drainage required that if the pump system failed due to a power cut, an independent system would be activated. Shown is the pipe work for the battery back-up system, again set below the shaft floor level.

One more pipe was set to carry the cables, and the sump was filled with 20mm drainage gravel.

A bitumen seal was applied to the block work to create a vapour seal for the membranes.

With the cavity drain membrane installed, one section of sheet was folded to create a basin to hold any hydraulic oil lost from the lift. The turn up of the membrane at its lowest point is higher that the total volume of hydraulic oil.

The end membrane installed and sealed to the bitumen for a vapour seal, and also to the sides and base, using a water proof over-tape.

The membrane was then cut to expose the sump cover.

Cavity drain membrane sealed to the sump basin.

Finished work in the lift shaft.