Case

Remediation of groundwater contamination in Central Denmark Region

Remediation of groundwater contamination in Central Denmark Region

Since 1999, Sweco has served as Central Denmark Region’s project manager for the remediation and monitoring of one of Denmark’s most severe trichlorethylene contamination incidents at a former industrial site in the town of Hedensted. The ongoing remediation measures include a reactive wall around the hot spot and a plant for pumping and stripping of groundwater from the contamination plume.

The groundwater under the site is contaminated with chlorinated solvents extending in a 2-3 km plume underneath the town of Hedensted. The purpose of the remediation measures is to remove the contamination in the groundwater and safeguard the indoor air quality in a large residential area located downstream of the industrial site.

A reactive wall is an onsite technology for clean-up of contaminated groundwater. A permeable reactive barrier is installed perpendicularly to the groundwater flow, consisting of a permeable treatment zone, which contains reactive material. When the contaminated groundwater flows through the reactive zone, contamination is retained in the reactive material or converted to less toxic or easily degradable substances. This way, the wall serves as a barrier to the contaminants but not to the groundwater flow.

As a supplement to the reactive wall, a remediation plant has been installed in the contamination plume in the form of horizontal filters in the secondary aquifer. The groundwater is then pumped to and treated by this plant.

Sweco’s team continuously monitors the groundwater contamination through documented water sampling in around 30 boreholes and sounding of the groundwater table in some 40 boreholes as well as operation of data loggers in 10 boreholes. The team also sample pore air under selected homes.

Sweco’s specialists continuously assess the analysis results and adjust the monitoring programme to ensure that the reactive wall and stripping plant are working optimally. Data are recorded and updated in Central Denmark Region’s database.

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