Zurich-West: The ewz Herdern Site Reimagined

Built in 1974, the oper­ations build­ing will not be demo­lished: it is being stripped back to its load-bearing con­crete struc­ture and compre­hensively re­newed. This approach con­serves resources and is in line with ewz's sustain­ability strategy.

Marti AG Zürich is leading the project and carry­ing out all struc­tural and special foun­dation works. Four com­panies of the Marti Group are work­ing together on the site, cover­ing comple­mentary fields of exper­tise, from decon­struction and asbestos removal to pol­lutant reme­diation and ground­water manage­ment.

Pre­cision work in a con­fined space
The decon­struction demands the utmost pre­cision from both crews and machinery. Remote-controlled demo­lition robots are deployed wherever pre­cision and safety allow no com­promise. Around 100 tonnes of asbestos-con­taining material and a further 3,200 tonnes of waste from the non-struc­tural decon­struction were removed and dis­posed of in strict com­pliance with regu­lations. The work was carried out using decon­tami­nation air­locks, fil­tration systems and a moni­tored fresh-air supply.

Engi­neering above Mühleweg
The archi­tectural centre­piece of the project is the canti­levered exten­sion: the pro­jecting main girders, resting on three inclined columns, were built on special heavy-duty false­work. Two new storeys were then con­structed on top. The canti­lever extends 35.68 metres over Mühleweg, with a clear height of 19.4 metres from the ground floor to the under­side of the pro­jecting struc­ture. Once com­pleted, the build­ing will mea­sure 128 metres in length, 23 metres in width and 29 metres in height.

Ground­water as an energy source
To build the enlarged under­ground car park, the ground­water table had to be tempo­rarily lowered: 16,000 litres per minute were pumped out, the equi­valent of some 80 bath­tubs per minute. After passing through a settling basin, the water is returned directly to the ground­water. In the long term, ground­water will become the build­ing's main source of energy: a new recircu­lation system, comple­mented by a photo­voltaic instal­lation of almost 2,000 m², will gene­rate around 160,000 kWh of solar power per year. The build­ing will meet the Minergie-P-ECO standard.