Site contamination – a major challenge, but one that can be overcome
The Klybeck site, known as the ‘cradle of colour and pharmaceutical chemistry’, has a chequered history. One hundred and fifty years of manufacturing and chemical and pharmaceutical research have led to the achievements that shape our lives today – but also left traces in the soil, groundwater and buildings.
Find out here how the past is being dealt with and what steps are needed to ensure the successful transformation of an industrial site into a vibrant mixed-use neighbourhood.
General conditions
Due to its history, a large part of the former chemical site is listed in the cantonal register of contaminated sites as contaminated and requiring monitoring. The statutory provisions, including the Federal Environmental Protection Act and the Contaminated Sites Ordinance, set out clear guidelines for dealing with contamination.
As long as the sealed subsoil remains undisturbed, there is no risk; however, risk assessments, safety measures, proper disposal and close supervision by the authorities are required for specific construction projects. Every construction project on contaminated land is assessed and monitored by the authorities.
This will ensure that, through the collaboration of all stakeholders – the owners, the authorities and the companies involved – the sustainable transformation of the Klybeck site into a new and liveable neighbourhood is a success.
Current status
Systematic surveys of the site are intended as a means of identifying potential risks to people and the environment at an early stage, with a view to taking action where necessary. They also help us to continuously review and expand our understanding of the status of contamination. The list of substances tested for is also reviewed on an ongoing basis and updated where necessary.
Thanks to these extensive investigations, the planning partners have a detailed picture of the status of contamination – both in the subsoil and within the buildings. The level of contamination varies depending on the location, geological strata and previous use.
There is currently a contaminated site that requires remediation. This concerns chlorobenzene contamination at Swiss Life’s site 3. The necessary remediation work is currently being prepared by previous owner BASF.
Some properties are already being put to new uses following the completion of remediation and refurbishment work. Others are still heavily contaminated as a result of their industrial past. In such cases, the pollutants are cleaned up and disposed of in connection with specific construction projects. This means that the properties can then be put to new use.
However, some of the buildings are so heavily contaminated that, in accordance with the ‘Städtebauliches Leitbild’ (urban planning model), they will be replaced by new buildings. The necessary demolition work is being carried out under strict safety precautions.
Since March, owners Rhystadt and Swiss Life have been making the results of investigations as well as documentation relating to site contamination publicly available via a data room set up for this purpose. The documents include the documentation made available to the two landowners at the time of their purchase of the site sections, as well as additional reports on completed procedures or key procedural steps commissioned by Rhystadt and Swiss Life in the course of the development project. This is the case, for example, with planned demolition and construction projects or in connection with the use of existing buildings.
Regular dialogue with various stakeholders – such as neighbourhood associations, local authorities, NGOs, and experts – regarding site contamination should also contribute to transparency and objective dialogue. To this end, Rhystadt and Swiss Life have set up ‘IAPSKA’, an information and exchange platform on site contamination at the Klybeck site.
Rhystadt: Site contamination Campus Klybeck: Site contamination
Rhystadt und Swiss Life
Rhystadt and Swiss Life acquired the former Novartis and BASF sites in 2019. Together with the canton of Basel-Stadt, they are transforming the Klybeck site into a green, mixed-use, climate-friendly neighbourhood. A key aspect of this regeneration is the proper management of building and subsoil contamination.
Where there are contaminated sites in the subsoil that require remediation, the owners are liable for the costs. By purchasing the land, they have committed themselves to implementing the necessary measures for the testing and disposal of hazardous substances. If responsibility for bearing the costs has not been conclusively determined, the Contaminated Sites Unit of the Basel-Stadt Office for the Environment and Energy (AUE) will, on request, examine the case and issue a decision on the allocation of costs. All measures required under the Contaminated Sites Ordinance – such as investigations, monitoring or remediation – must be notified to the AUE as the competent enforcement authority. The AUE must be informed of the outcome of these measures, before assessing whether this complies with existing legislation or whether any adjustments are necessary.
In the case of construction projects that involve disturbing contaminated soil, or when removing hazardous substances from buildings, property owners are required to carry out a thorough investigation of the contamination beforehand and to commission expert reports on how to handle and dispose of the contaminated materials.
Basel-Stadt Office for the Environment and Energy (AUE)
The AUE is the cantonal supervisory authority for environmental and energy matters. Its core responsibilities include water protection, wastewater management, waste management, remediation of contaminated sites, soil protection, energy efficiency and noise protection.
For every construction project, the AUE sets out binding requirements, particularly with regard to contaminated sites requiring remediation as well as any other site contamination issues. On sites with higher levels of contamination, a construction-related risk assessment is required to demonstrate compliance with environmental legislation and the Contaminated Sites Ordinance. In addition, a plan for excavation, sorting and disposal, as well as a health and safety plan, are required.
If the existing studies are insufficient, further investigations must be carried out before construction begins. Only after carrying out an assessment in accordance with statutory requirements will the AUE grant approval for a construction project to go ahead. All construction projects are closely monitored by the regulatory authorities.
Building and Hospitality Inspectorate of the Basel-Stadt Department of Construction and Transport (BVD)
The BVD is responsible for reviewing planning applications. It also coordinates all comments and conditions issued by the specialist departments involved in the planning application. Construction projects where contamination is suspected require, if sufficient information is not available, additional preliminary investigations as well as plans for dealing with contamination.
Air Quality Office
The Air Quality Office, a joint agency of the cantons of Basel-Landschaft and Basel-Stadt, monitors air pollution levels and trends – and is therefore responsible, for example, for monitoring potential emissions of air pollutants during demolition and construction work.
Why is the Klybeck site considered to be contaminated?
For over 150 years, the Klybeck site was an industrial hub, initially for dye manufacturing and later as a major production and research centre for the chemical and pharmaceutical industry. During this period, substances were used that are now considered harmful to the environment or to human health.
What is the current situation on the site?
The Klybeck site is continuously monitored, with the former industrial site listed in the cantonal register of contaminated sites as contaminated and requiring monitoring. This monitoring is carried out in close consultation with the relevant cantonal authority and complies with the applicable regulations. This monitoring programme comprises comprehensive, regular groundwater monitoring and is continually supplemented by further investigations and analyses.
Are there any site contamination issues and, specifically, contaminated sites that require remediation on the Klybeck site?
The site is classified as contaminated and requiring monitoring. This classification requires the owners to carry out regular inspections. There is currently a contaminated site on the premises that requires remediation: a chlorobenzene contamination at site 3. Preparations are currently under way for the remediation of this contaminated site.
How long does it take to clean up a contaminated site?
That depends very much on the nature and extent of the contamination. Typically, a remediation project spans several years, from the preparatory phase through to implementation and monitoring of the remediation objectives. The work takes so long because thousands of tonnes of material and groundwater have to be pre-screened, analysed, excavated or pumped out where necessary, treated and disposed of, all under strict safety precautions.
How do the investigations work?
The level of contamination at the former Klybeck industrial site is well documented, and the handling of contaminated materials and soil is governed by comprehensive and detailed regulations. The industrial site is being monitored in close consultation with the cantonal authorities, with the monitoring system being continuously expanded to include further investigations. For example, comprehensive indoor air quality tests are being carried out at the existing temporary occupancies to ensure that premises can be used safely at all times. The groundwater on the site is also being constantly monitored. Furthermore, surveys and trial remediation projects are being implemented on existing properties as part of the development and planning work, with further investigations to be conducted once a specific building project has been identified. These investigations are very comprehensive, are tailored to the specific building project wherever possible, and also address which substances might be released during the construction phase.
Who will bear the costs of the remediation work?
In principle, owners Rhystadt and Swiss Life will bear the costs of remediating contaminated sites.
How can we ensure that future users of the site are not exposed to any health risks?
The owners may only build in areas where it has been established that there is no longer any danger. Clear statutory limits have been set for this. Only once the requirements have been met will the Basel-Stadt Office for the Environment and Energy approve the site for use.
Which independent bodies are overseeing the remediation work?
The Basel-Stadt Office for the Environment and Energy (AUE) is the main authority supervising the remediation work. Its responsibilities include reviewing the expert reports, assessing risks and, where necessary, setting out binding measures. Implementation of these measures is monitored on an ongoing basis. The AUE may also engage external specialist firms to independently review compliance with the relevant requirements.
How sure can people in Basel be that the subsoil will actually be remediated?
The planning partners are aware of their responsibility in dealing with site contamination and are guided in the remediation process by the strict statutory provisions on site contamination laid down by the federal government and the relevant authorities. As part of the regeneration project, the Klybeck site is set to become a green, mixed-use, climate-friendly neighbourhood where current and future generations can live safely and healthily.
Remediation will be considered wherever necessary and feasible. However, under the Contaminated Sites Ordinance, remediation does not always involve excavation, and experience shows that this is not necessarily always the best option. Nevertheless, the plan is to eliminate site contamination wherever possible. ‘Sham remediation’ is out of the question – nor is it tolerated by law or under the AUE’s supervisory mandate.
Why aren’t contaminated buildings systematically demolished?
Whether demolition is the most sensible option for a contaminated building on the site, or whether it should be dealt with in some other way, is part of a comprehensive planning process being carried out by the landowners in collaboration with the authorities. The aim is to take into account not only pollutants but also building quality and sustainability considerations. Current and future use must always be considered when dealing with buildings contaminated with hazardous substances. Contaminated sites may only be developed or altered if this does not result in them requiring remediation, or if remediation is carried out at the same time as the development. When planning a refurbishment, a demolition or a new build, it is necessary to determine during the preparatory work whether any contaminated materials are present and, if so, in what form. On this basis, the relevant remediation and protection plans are then drawn up and submitted to the relevant authorities. In addition, further samples will be taken from the contaminated materials during remediation and demolition work, and the remediation steps will be planned in detail and carried out.
How is the public being kept informed about the status of contamination?
In March 2025, owners Rhystadt and Swiss Life published comprehensive information on the status of contamination at the Klybeck site. Around 200 reports are available to the public. Further events addressing the issue of site contamination will also be held. These will focus on dialogue with stakeholders.
What happens if further harmful substances are discovered during construction?
Before building can begin, the owners must carry out a detailed assessment of the building site and any potential contamination, and submit a remediation plan. If additional pollutants are nevertheless discovered during the construction work, a clearly defined procedure will come into effect, involving a halt to work in the affected area as well as immediate notification to the Basel-Stadt Office for the Environment and Energy. Construction work may only continue once a risk assessment has been carried out and the remediation measures are determined. This ensures that people and the environment remain protected at all times.
Is there a health risk to the public while the remediation work is still ongoing?
The site has been thoroughly investigated. The monitoring programmes are designed to identify potential risks to people and the environment, and to enable action where necessary. Based on current knowledge, there is no risk to humans or the environment. All accessible areas or buildings can be entered without any danger.
Sites requiring remediation
This refers to contamination in the subsoil that is classified as requiring remediation due to its harmful effects on people and the environment. Contaminated sites are often found underground, but only a small proportion of them are legally classified as contaminated sites that require remediation to eliminate or mitigate the risk. Usually, the term ‘remediation’ is only referred to in relation to genuinely contaminated sites. The simple removal of contaminants is known as decontamination or, simply, disposal.
Contaminated Sites Ordinance
The Contaminated Sites Ordinance (CSO) is a federal ordinance governing the management of contaminated sites. It is intended to ensure that contaminated sites are remediated if they give rise to harmful or nuisance effects, or if there is a real risk that such effects may occur. The Office for the Environment and Energy (AUE) is the competent enforcement authority in the canton of Basel-Stadt.
Contaminated sites
Contaminated sites are locations where the subsoil contains pollutants originating from waste, but which do not pose an immediate hazard. Contaminated sites are usually limited in size. They include disposal sites, operational sites and accident sites.
Building pollutants
These are harmful substances found in buildings, parts of buildings, or building components that can have adverse effects on people and the environment. A distinction is made between pollutants resulting from the building itself (like asbestos) and those resulting from its use, which have, for example, penetrated the building fabric during chemical production. Switzerland is no exception, in that the handling of hazardous substances in buildings here is, likewise, subject to specific rules and regulations designed to protect human health and the environment. However, the Contaminated Sites Ordinance deals only with pollutants in the subsoil and the environment, and contains no provisions regarding the investigation, handling and disposal of building pollutants.
Register of contaminated sites
The cantonal register of contaminated sites is a source of information on soil contamination resulting from past land use. It provides information on whether a site is contaminated and whether it requires further investigation, monitoring and/or remediation. The federal Contaminated Sites Ordinance requires every canton to draw up such a register.
Site contamination
Site contamination refers to pollutants found in the subsoil and/or groundwater at a specific location that may be harmful to people and the environment. They are caused, for example, by industrial production, waste disposal or the improper use of chemicals.