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Sanitation of waste deposits ARGE W18 - Gasworks Simmering

Facts and Figures
Company PORR Umwelttechnik GmbH in a consortium
Principal Wien Energie Gasnetz GmbH
Location Vienna - Austria
Type Remediation of contaminated sites
Runtime 10.2010 - 04.2012

100,000 t of residual waste secured

Between 1899 and 1975 the city gas was produced at the site of the Wien Energie Gasnetz GmbH in  Vienna-Simmering. Thus, environmentally hazardous by-products or residues such as tar, gas purifier mass and ammonia water was deposited on the site. During World War II parts of the Gasworks were damaged - among others, the coverings of the bricked gas tanks were burned down, the light oil plant was destroyed and the tar cistern partially collapsed. The remaining contaminated debris were mostly deposited on the site or used for backfills. Due to product residues, deposits, manipulation losses and as a result of war damage large areas of the old industrial site were contaminated. Typical pollutants included particularly PAHs, as well as phenols, BTEX and cyanides. In the area of the former Gasworks and its vicinity there are numerous groundwater utilizations partly as industrial water and for irrigation purposes.

A total of 187 ramming core samplings were made in order to determine the contaminated areas. On the entire area of the old industrial site anthropogenic mounds of up to 7.2 m thickness were found. The eastern part was contaminated through massive tar oil components. Particularly in the area of the tar cistern there was a seepage of large amounts of tar oil in the subsoil. In places with low permeability subsurface layers the contaminants reached the ground water body at depths exceeding 10 m. Here the tar oil  had spread laterally as well, depending on the surface topography of these layers.

The greatest exposures to PAHs were detected in the former tar and ammonia cistern, at tar tower, at tar sheath and ammonia scrubbers building, and part of the light oil scrubber plant. In the area of the former tar and ammonia cistern, the tar tower, the light oil scrubber plant and the coal scrubber building massive deposits of hydrocarbons were also detected. The contaminations of the subsoil with cyanides were distributed over the entire site. Selectively, contaminations with phenols, ammonium and sulphate were also detected. These resulted in severe groundwater contamination.

By means of two locking fountain rows hydraulic safety of the site has been achieved. The aim of the measures was to ensure long-term usability of downstream groundwater. As preparation for this purpose those areas have been cleared in which based on the risk assessment the highest pollutant concentrations and the potentially most mobile contaminants were present. This includes in particular the former tar or ammonia cistern as well as some hot-spot areas.

The total excavation amounts to approximately 100,000 t