Environmental-technical consultancy services on the water quality improvement of waterway ‘De Vaart" ordered by water board ‘Hoogheemraadschap Hollands Noorderkwartier’.
Waterway ‘De Vaart’ has been classified as a surface waterbody under the EU Water Framework Directive. The quality of the environmental was threatened by high metal concentrations and increased levels of (polycyclic aromatic) hydrocarbons. By Tauw sediment cores were taken to characterize the internal layered structure and the extent of the contamination. Consequently, an environmental risk assessment was performed to determine the proportion of the water contamination by diffusion at the soil-surface water interface with the use of software program ‘SEDImentASsistent’ (SEDIAS). In combination with geotechnical location inspections, results indicated that action had to be taken to ensure the standards for water quality.
Tauw developed a customized recovery action-plan that formed the base for the executive proceedings with Computer Aided Designs (CAD) in order to remove as much contaminated sediment as possible and prevent shores from collapsing. In the period from January until March 2017, over 11.000 m3 of sediment was remediated. To finish the project, a thin 0,3 m sand layer is deposited to cover the area of around 2.5 hectares to prevent future diffusion of left contaminants to surface waters and oxidation of peat. Also, the sand layer will improve water clarity, since resuspension is limited.
Finally, control measures taken in waterway ‘De Vaart’ will have a positive environmental impact on the biodiversity and shores