The former Josefstrasse waste incineration plant left pollutants underground.
Increased dioxin levels have been measured in the deeper soil of the Josefwiese.
The soil of the Josefwiese in Zurich District 5, which is popular far beyond the neighborhood as a recreation area, is partially contaminated with dioxin – an environmental toxin that is produced during combustion processes and is hardly broken down in the soil. The values in the deeper layers of the earth are in a range that slightly exceeds the test values and therefore requires an in-depth investigation in the next few months, as the canton of Zurich reports. However, the meadow can be used as before.
This year, the canton had playgrounds, parks and school grounds in the vicinity of waste incineration plants randomly tested for dioxins; the Josefwiese is located right next to the former Josefstrasse waste incineration plant. It is the oldest such facility in Switzerland; last spring it was shut down after almost 120 years of operation.
The background to these investigations is the very high levels of dioxins that were detected in the early summer of 2021 in the vicinity of the former waste incineration plant in Lausanne. They probably originate from flue gas emissions from previous years of operation.
The numbers were alarming: in some places dioxin levels of over 600 nanograms per kilogram of soil were measured; According to the national ordinance on soil pollution, values from 20 nanograms are considered potentially dangerous for humans and animals. Extensive soil remediation is therefore necessary in Lausanne.
Things are different in Zurich. The tests on the Josefwiese showed that the test value was maintained in the top five centimeters of the soil layer and that the current use of the meadow is therefore unproblematic. At a depth of up to 20 centimetres, on the other hand, the test values of 22.5 nanograms per kilogram of soil are slightly exceeded. For comparison: From a value of 100, the use of the Josefwiese would no longer be possible.
“The ground on the Josefwiese is covered with grass, so the probability of picking up contaminated soil material is low,” says Wolfgang Bollack, media spokesman for the building department. Although the test values are only slightly exceeded, it still makes sense to examine the topsoil more closely.
No problematic values were detected on the other areas examined in the canton. At the Unterer Letten river pool and at the bakery, dioxin levels above the guideline value of 5 were found, but they are well below the specified test value and do not pose a risk with the current use of the areas.
Efficient filter systems have been prescribed for waste incineration plants since the mid-1980s. As early as the 1990s, the canton examined soils in the vicinity of the Hagenholz waste incineration plants in Zurich and Hinwil. At that time, too, the loads determined were below the specified test value. As the canton reports, the investigations carried out this year confirmed the results of earlier measurements.