New high-rise building, Zurich Complete decontamination as part of a tightly scheduled construction project

The project

Location: Zurich-Altstetten (ZH)
Customer: UBS AG
Phases: Preliminary investigation, submission, specialist support, contaminated site remediation
Duration: 2017-2019
Building costs: --


As part of a new-build project in the city of Zurich, the former commercial premises had to be demolished and the entire site decontaminated. Assessments revealed the existence of extensive slag backfilling under the building as well as localised production-related concrete and soil contamination. As part of the excavation works, further localised contamination came to light that needed to be removed during the excavation works. An area of mineral oil hydrocarbon contamination emanating from a former soakaway, which extended beneath the planned excavation into the aquifer, presented particular challenges. Ecosens AG provided support across all stages of the project, from preliminary investigation and planning to implementation.


Our services

  • Undertaking a preliminary investigation of the contamination present (concrete slabs, asphalt, topsoil and earth)
  • Creating a process and decontamination plan
  • Preparing an estimate of additional costs for the excavation tender
  • Organising and managing the site remediation in collaboration with the main contractor and engineers
  • Specialist earthworks management, including final documentation for “independent monitoring”


  • Required additional excavation work up to a depth of approx. 4.0 m beyond the planned excavation, required to ensure the deletion from the Register of Contaminated Sites as required by the contract
  • The area of oil contamination beneath the excavation to a depth of approx. 7.0 m (in the aquifer) à Rapid planning and implementation of remediation works using sheet pile enclosures, including coordination with the authorities
  • Overall, a tightly scheduled construction project with difficult spatial constraints, high cost pressures and challenging coordination between contractor, construction manager, the other contractors and planners involved

Project manager:

Melanie Vögtli Co-divisional manager: Contaminated sites
MSc Environmental Engineering, ETH (Federal Institute of Technology) +41 44 839 47 71 More