February 1958: The construction of the Guérinière water tower

The Guérinière water tower was built in the wake of the Second World War by the brutalist architect Guillaume Gillet. Jason Ford recalls how The Engineer reported on both its functionality and its aesthetics

Three quarters of Caen was destroyed during the latter stages of the Second World War, and a feature of its reconstruction is arguably as brutal as the bombardment that flattened the  Normandy city. Resembling a giant shuttlecock at rest in a concrete ring, the water tower at Caen-La Guérinière counts renowned brutalist architect Guillaume Gillet as one of its designers, and is one of a long list of buildings that were built for the same utility whilst combining aesthetics as well as functionality.

Guérinière water tower

In fact, the water tower was built to accommodate subsidiary functions such as a sub-post office, shops, and several offices, in addition to providing a high and low-pressure system that would operate during periods of drought.

Our correspondent reported that 2,200 dwellings were being built by local authorities in the southern suburb of La Guérinière to accommodate approximately 10,000 people. Construction by private companies was also taking place, and the increase in demand for water created difficulties in supplying higher parts of the town on the right bank of the Orne river.

The Engineer noted that drops in water pressure were severe during periods of drought, when the normal supply of 12,000 cubic metres per day decreased to approximately a third of that.

“Accordingly, it was decided to construct a water tower which would allow the available supplies to be apportioned between the high and low-pressure zones according to any desired schedule,” our correspondent wrote, “and supply the high-level zone at an increased head, while the low-level zone would also receive water from the tower but with a lesser head.”

The total weight of the building – including water – amounted to approximately 5,000 tonnes, and ground pressure at the central footing was estimated at 10kg/cm2.

The comparatively large size of the reservoir was accounted for by the fact that its water was destined for the two supply zones. From the rising main, incoming water reached a weir fitted with a splitting plate to divide the flow between the two systems.

The high-pressure flow, according to The Engineer, went into the reservoir, from where it was withdrawn by a 500mm diameter downpipe. The low-pressure flow entered the central pipe, along with any overspill water. Since the water level in the central pipe varied between “30m and 49m sea level”, the water – if allowed to cascade into this pipe – would entrain air, which could disrupt the distribution system.

Guérinière water tower
Guérinière water tower

“To obviate this, the inlet was arranged to give a spiral inflow, so that the water descends in a helical path at an angle of one in five, being held to the pipe wall by centrifugal action,” our correspondent said. “In this way, very little air is entrapped and any such air can rise and escape up the centre of the vortex.  The reservoir is prevented from overflowing, in case of serious unbalance between inflow and withdrawal, by a shut-off disc valve equipped with a float and arranged so as to give a gradual closure and avoid water hammer.”

As well as function, this publication paid attention to the tower’s construction, describing the reservoir more formally as “an inverted circular truncated cone”,  which was designed to rest on 16 equally spaced columns rising from the centre foundation in the direction of the generating lines of the cone.

Horizontal extensions of these columns at first-floor level stabilised the tower vertically, supporting the conical roof under which the market was to be installed.

“In turn, the beams rest on an elliptical ring of columns,” The Engineer wrote. “A platform, cantilevered from the columns, carries a single-storey structure which is intended to house a number of offices of the municipality, a sub-post office and similar facilities.

“The building thus fulfils three functions, of which the two subsidiary ones have been ingeniously harmonised with the principal objective.”

Readers’ concerns about stability were allayed with remarks on the building’s construction. For example, the horizontal extensions of the supporting columns were observed as being joined flexibly to the outer ring of columns on which they rested.

“Another series of flexible joints is provided at the base of the outer columns,” noted our correspondent. “The weight of the cantilevered portion of these columns, together with that of the superimposed offices, balances the outward force on the main columns together with the effect of wind pressure.

“Buckling of the very slender main columns is resisted by stiffener rings, the upper two of which are placed along the inner edges of the columns while the middle ring extends across the whole column width.”