The cistern is a circular space with an internal radius of 4.5’ and height of 7’. The walls are made of 27” rammed earth tires in a running bond pattern with an internal 8” concrete layer to provide a waterproof barrier. The use of a circular shape creates a geometrically stable shape where no buttressing is needed. In addition, it allows to avoid the presence of sharp corners where stresses would accumulate in case of earthquakes, thus creating weak spots in the structure. A 10” deep concrete bond beam is poured atop the tires to tie the structure together.

The first two courses of tires in the cistern walls are filled with gravel in order to provide a solid footing for the walls while preventing any water infiltration via capillary action. Similarly, the 10” deep concrete cistern slab is poured on a layer of gravel. The sediment box from where the water can be pumped extends 2’ below the concrete slab, through the gravel layer into the ground.

The cistern is topped by a 10” concrete circular slab resting on the concrete bond beam and a 8” deep concrete beam crossing the slab in its centre. This additional beam also hosts respirators that let air in the cistern if it is sealed when the water is pumped out.

The cistern is fed by the rainwater collected on the adjacent roof as well as the water coming from the part of the water network located at a higher altitude. There are two outlet pipes: one feeding by gravity the buildings located at a lower altitude, and one connected to a pump system to feed the part of the network located at a higher altitude.