The city of Berlin squats on a flat plain with a very high water table. This has meant that for nearly a hundred years drainage and sewage have been distributed by mechanical pumping. The city has 140 pumping stations, some approaching 100-years-old, standing as wonderfully robust monuments to its industrial past. The old red-brick station at Wilmersdorf, on the west of Berlin in the heart of a densely developed urban district, was built in 1903-6. Although its structure is sound, the equipment has reached the end of its life.
Following a proposal to build a new pumping station next to the old one, which is being converted into a technical museum, the Berlin water authority organised a competition. This was won by the Munich architect Ackermann und Partner.
In a deliberate contrast to the cathedrallike proportions of the old station, the new building announces itself as a delicate steel and glass structure, two-storeys high. The interior - a gallery resting on a mezzanine - is visible through a glass facade that minimises the impact of the bulky 20 x 40m building. The gallery is open to the public and while most of the visitors are expected to be schoolchildren, it can also be used for exhibitions, book launches or small parties.
A visit to the gallery gives a true picture of the building. Running along each side of a huge well, the gallery measures 8m wide and nearly 40m long. Look over the railings and a Piranesian underworld is revealed, containing pumps, ducts, generators, sewage tanks and plant. This is where the real technical business is done.
Staircases and gantries in the central well give access to the four levels of plant. The vast basement is flanked by concrete walls measuring more than a metre thick. The whole basement block was cast above ground as a caisson and then lowered 18m to its final position by flushing out the sandy sub-soil beneath it. Although this may seem a relatively unusual construction method, it is frequently used in Berlin because of the high water table.
Above ground, the mezzanine - a solid enclosure formed of concrete slabs supported by sheer walls and composite steel columns - runs at the sides of the central well. The first-floor gallery, with its steel structure, sits on top of the mezzanine.
Clearly visible through the glass skin, it consists of four 20m triangulated truss girders, which bridge the central well. These are supported at each end on trestle-like props with canted legs (see Working Detail). The connection between the trusses and the props - the most visible part of the structure - is made by an articulated cast-steel node, giving the structure a machine-like quality; a reference to the great pumping machines below. The composite roof is fitted with a series of large rooflights above the well.
These are fitted with prismatic glass, which directs daylight into even the deepest parts of the basement.
Because it is closely surrounded by houses and flats, the huge glass facade of the pumping station was designed to provide sound insulation and save energy by exploiting solar gains. It consists of two separate glass layers. There is an external layer of 15mm toughened glass sheet connected by stainless steel structural bolts, an intermediate space 700mm wide that allows for maintenance and gives a means of escape in a fire, and an internal skin of steel-framed doubleglazed units.
The facade support structure is independent of the main building. It uses a series of 200 x 30mm steel columns at 3.3m centres on the outer layer of the facade, braced at the corners with tension rods. Similar columns at 1.65m centres support the inner layer.
Although there are no permanent workplaces in the pumping station, temperature extremes had to be avoided. Even under exceptional weather conditions, the doublelayer steel and glass facade is designed to maintain an internal temperature of about 14degreesC. No additional energy is used to keep this temperature constant. The six electric and diesel pumps emit 199kW of waste heat, with a total capacity of 20,000 m 3/hour.
ARCHITECT Ackermann und Partner
PROJECT ARCHITECTS Christof Simon, Eoin Bowler
STRUCTURAL ENGINEER Buro Happold, Bath and Happold Ingenieurburo, Berlin: Terry Ealey, Michael Vitzthum