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unilogo Universität Stuttgart
Institute of Hydraulic Engineering

Research: VEGAS - Research Facility for Subsurface Remediation

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Field Site "THERIS-I"
Project manager:Dr.-Ing. Hans-Peter Koschitzky, AD
Research assistants:Dr.-Ing. Uwe Hiester
Dr.-Ing. Arne Färber
Duration:1.10.2003 - 31.5.2004
Comments:

This project is part of the research area:
In-Situ Remediation Technologies

Publications: Link

Abstract:

The first THERIS-field application was carried out in 2003/2004 at a former dry cleaners site with a CHC contamination in the unsaturated zone (UZ) in an urban, densely populated area. During the 50s and 60s of last century, primarily tetrachloroethene (PCE) has been spilled in the subsoil. The rehabilitation by a conventional "cold" soil vapour extraction (SVE) failed because of the low permeability of the subsoil and the limited availability of pollutants in the gaseous phase. The pollutant concentrations exceed locally the soil remediation target of 5 mg / kg soil by a factor of more than 30.

The geological structure at the site starts from the top with a sandy layer including demolishing material. The second layer down to about 2 - 2.5 m b.g.s. consists of fine sand and silty sand. This is underlain by a cohesive layer of sediment of about 4 to 4.5 m followed by a clay layer (marl) and from 6.5 m b.g.s. medium sand. The groundwater table is approximately at 11 m b.g.s. The highest concentrations were available at the bottom of marl and silt.

The target area which has to be remediated with the THERIS method was between approximately 4 and 6.5 m b.g.s. in the marl and the underlying silt. The remediation field had an area of approximately 80 m2. The in-situ remediation with the THERIS method should be completed within a few weeks. The remedy was successful within three months and was confirmed by the supervising authority. At this time, the average soil concentration was far below the remediation target value by more than an order of magnitude. The pilot application of THERIS procedure was technically very successful and proven in the field. An assessment of the economic and environmental success can be found in (Hiester, 2009). The rehabilitation time with the THERIS method compared to the projected recovery time with the "cold" SVE was reduced by more than an order of magnitude.